Does a mountain top have higher gravity than a nearby sea-level surface? Regardless the latitude and centrifugial 'force' is the gravity on mountains higher or lower than at sealevel?

Gravity is depending on the radius to the centre and the mass. Now if you are on a mountain you are further from centre but it looks like you have more mass under you. Probably the differences would be tiny but is it likely that on mountains the gravity is higher or lower than at see level? As far as I could see till now where there are mountains the gravity is lower, but are there mountains where the gravity is higher?

I gave this one some thought and ran some numbers.

The real answer to your question is that you would be lighter because the material that makes up continental plates is lighter than the basalt rock under it.  It might not look that way but continents, mountains and oceans are actually balanced with about equal weight under them.  Continents are above sea level because of larger amounts of crust which is lighter than basalt.  The earth, which is pretty malleable as a whole, adjusts for significant unbalanced changes in mass, it's still rebounding from the melted glaciers from the last ice age for example.

This happens with Mountains too, also slowly, but mountains are formed over millions of years so the adjustment has time to take place.  Mountains are formed when two continental plates push against each other, one slides under the other, so both what forms the mountain, and what goes under the mountain is lighter than basalt under the Earth's crust.   When you climb a mountain, you're not actually on top of more mass because much of the rock under you is lighter rock.  Mountains are actually puffy (I always wanted to say that).    If mountains were actually greater mass relative to the (relatively) spherical Earth, then they'd sink into the Earth, which they do to some extent, but, as I said above, Mountains are puffy buoyant compared to the Earth's crust, so the mass is pretty much the same on top of the mountain and at the foot of the mountain.

That's not to say the Earth is perfectly balanced, it's definitely not, but the imbalance doesn't appear to follow mountain ranges.  Google "Earth Gravity Map" for more on that.  Article with pretty picture here.

But I suspect, your question wasn't just real world but also a mathematical query, so, moving on.   If we create a cone shaped mountain, a large flat one, lets say it's 6.371 km tall (reason I picked that number will become clear soon), and lets give it 4 times that as a radius or 25.484 km radius to it's base and a specific density of 2.7, the mass of our mountain, using 1/3 base times height is:  3.1416 * .333333 * 2.7 * 25,484^2 * 6,371 * 1000  (the 1,000 is for density of 1,000 KG per cubic meter at specific density of 1) = about 1.17x10^16 KG.

So, on top of this artificial mountain that, if it was actually added to the earth, it would push the earth down and the earth would adjust it's mass around it over time, but ignoring that, the mountain is 1/1000th the radius of the earth so the distance from the Earth's center is increased by 0.1%

The mass of the mountain, 1.17E16kg is about 1/510,000,000 the mass of the Earth, 5.97E24kg, So we have a mass increase of about 0.0000002% and a corresponding reduction in gravitation by increased distance to the center of the earth (the square of 0.1%), or 0.0001.   or, 510 times as much is lost by the higher altitude than is gained by the increase in mass.  Now if you make the mountain flat enough, you'd probably be able to increase gravity the tiniest bit, but past a certain point the foot of the mountain is so spread out that the calculation grows inaccurate.  The short answer is simply, no, as the other two posters have said.  The mass of any mountain is simply insufficient to increase the force of gravity more than it loses by what's lost in the higher altitude.

A 3rd real factor, completely unrelated to your question is air density.  Heavier air does create some buoyancy which reduces our weight and the gravity we feel, this effect varies with high and low pressure and temperature, but on an average day at sea level air buoyancy reduces our mass by about .12%, so if you weighed yourself in a vacuum chamber vs your regular bathroom routine, you'd find you weigh about 2 or 3 ounces more for an average person.   Climb a mountain, the thinner air, you might gain an ounce due to loss of air buoyancy and that more than makes up for any small changes in gravity, so if you measure gravity by a scale and a weight, things weigh more on top of a mountain, because of thinner air, even though the G force is slightly lower.

The rotation of the earth and the centrifugal force also decreases mass, depending on how close the mountain is to the equator, (see picture).  as does the bulge of the Earth around it's equator, but all these changes are tiny.


Would oceans regenerate if removed? On Earth, there is enough Hydrogen and Oxygen to make 13,88 million km$^3$ of water (calculation below). However, oceans contain only a tenth of that.

Clearly, most of the hydrogen must be stored in other chemical compounds different to water. Or, as water deep within Earth's interior: some studies suggest the water on Earth's interior could contain three times as much as the water near the surface.

On the other hand there are many chemical reactions, like the well known photosynthesis and respiration, that can transform water into other compounds and vice versa.

We often think that there is a fixed amount of liquid water on Earth (plus or minus what is being recycled in the atmosphere). But it seems to me that the processes above could change the water amount significantly over geological timescales.

So my question could be stated as follows: over geological timescales, what determines the amount of liquid water on Earth?

Here are two examples of the processes I'm thinking about:

Reservoir transfers: If water from a well is removed, the ground water reservoir around it will slowly re-fill the well. Would the same happen with Earth's oceans if removed? Would water from the deep Earth's interior partially re-fill the oceans through volcanic eruptions?
Chemical balance: For a chemical reaction that can go both ways, if the reactants and products are in equilibrium and I remove the product compounds, more of them will be generated until a new equilibrium is reached. Would the same happen if I remove the water from Earth's surface? Will Hydrogen and Oxygen from rocks and air combine to partially replenish the oceans?

(This question was inspired by How much water is the atmosphere losing to space?)

Calculation of the maximum possible water on Earth

The maximum amount of water you can have on Earth is limited by the available hydrogen. Now, for each gram of bulk Earth there are 260 $\mu\text{g}$ of hydrogen and plenty of Oxygen.

Given that the Earth's mass is $5.972 \times 10^{27}$, and 260 $\mu\text{g/g}$ correspond to Hydrogen, that would total $1.552 \times 10^{24}$ g of Hydrogen, that at a molar mass of 1.007 g/mol, corresponds to $1.540 \times 10^{24}$ mol, enough to make $7.703 \times 10^{23}$ mol of water (as two atoms of hydrogen are required in a molecule of water). And since water has a molecular mass of 18.0152 g/mol, such an amount of water would weigh $1.3877\times 10^{25}$ grams. Finally, assuming a density of 1 $\text{g/cm}^3$ we get a total of $1.3877\times 10^{25}$ $\text{cm}^3$ or $13,877,025,731\, \text{km}^3$; that corresponds to 10.01 times the amount of water near Earth's surface (including oceans, lakes, rivers, ground water, etc.) and that is estimated to add up to 1,386,000,000 $\text{km}^3$.

I'm ignorant of all the organic and inorganic chemical reactions that can destroy or create water, and the factors controlling them. But I can give a shot to the part of the question related to volcanoes and the water stored on Earth's interior:

The most abundant gas in volcanic eruptions is water, corresponding to more than the 80% of emitted gases in volume (source).
If we consider on of the largest volcanic eruptions we know about: The toba supervolcano eruption 75,000 years ago. The water volume emitted has been estimated in $540\, \text{km}^3$.

Figure: Comparison of ejected material from notable eruptions (source)

From that perspective, you can see that you would need about 2.5 million Toba eruptions to re-fill the oceans.

In the past, over the history of Earth it could be reasonable to think that the volcanic output could average to the equivalent one Toba eruption every 2000 years, something that would be enough to deliver the volume of water currently in the oceans, but over 4.5 billion years.

However, most volcanic activity on Earth is related to subduction volcanism (including Toba), and such volcanism relies on water input to produce the erupting magmas, and arguably, a large fraction of the erupted water is the same water that was lost in the corresponding subduction zone.

We can then conclude that volcanic water input could eventually help keeping the level on a drying ocean, but at a very slow rate and over very long timescales. But if the oceans ever go dry, volcanism is unlikely to revert the situation.

In the context of the question that motivated this one, the rate at which volcanoes release water dwarf that of water losses to space. However, over long enough times those losses could dry our both the ocean and the Earth interior. But more importantly, I don't know if the net transfer of water from/to the Earth's interior is zero (in balance) or if the mantle is actually sucking water from the oceans, or filling them up. It might be that instead of worrying of planets loosing their water to space, we should worry about them loosing it to their guts.


How much of the underwater land masses within the arctic ocean is considered continental shelf? Right now I'm in the middle of writing my master thesis which is about modelling the ocean bottom pressure (obp) under areas with sea-ice coverage.

In most Oceanic General Circulation Model's (ogcm) obp is calculated prognostically, so it's basically just the sum of the sea-surface height $\zeta$.

Recent studies show an increase in $\zeta$ for regions with continental shelf within a reasonable timespan, so I was wondering how much of the arctic sea is above continental shelf? I know it is probably a lot, but are there any numbers, units of $\text{km}^{2}$?

Yool & Fasham in An Examination of the Continental shelf pump in an open ocean general circulation model Global Biogeochemical Cycles Volume 15, Issue 4, pages 831–844, divide the continental shelves into 32 named regions (see Fig. 2), and give areas for each (see table 1).

The regions that are completely in the arctic ocean are:

Russian arctic shelf 1,503,000 sq. km.

Siberian arctic shelf 1,825,000 sq. km.

North American arctic shelf 498,000 sq. km.

There are three other regions that are partially in the arctic ocean,

Iceland and Greenland shelf, North Sea shelf, and Berring Sea shelf, but looking at Fig. 2 and table 1 these seem like small contributors.

Roughly 4 million sq. km total.


How stable is the Gulf Stream? Could it stop suddenly? I'm not completely clear on what Western intensification means, but it looks like a pretty powerful (combination of) forces that presumably wouldn't be likely to change on a timescale of years (or even decades, centuries).

But I recall reading some time ago that global warming is already known to be causing a significant increase in the amount of fresh (as opposed to salt) water being introduced into the system at the European end. I assume that's "one-time-only" melting of glaciers and snow/ice in areas that were previously permafrost, but for all I know there could be much more simply arising from a (potential) massive increase in precipitation across north-western Europe.

I freely admit I don't know the relative importance of warm/cold salty/fresh water in the thermodynamics of the Gulf Stream system, which is probably relevant. But what I really want to know is...

  Do we understand the Gulf Stream well enough to answer the question posed in my title?

There's a pretty good rundown of this issue over at RealClimate, and a wikipedia article dedicated to the topic.

A summary of the main points from there:

The Gulf Stream is part of the Meridional Overturning Current (global ocean conveyor), which is primarily wind-driven, and secondarily thermohaline-driven. The Gulf Stream itself is also primarily wind-driven.
There has been some reduction of the thermohaline drivers in the north Atlantic, due to increased temperatures, and influxes of fresh water, largely from melting of the Siberian permafrost. This part of the system does fluctuate (as do most parts), but there does appear to be a trend.
These changes are not enough threaten the Gulf Stream, and there hasn't really been any observations of an over-all slow down that couldn't be otherwise explained by natural variation.
It is likely that the Gulf Stream will slow down over the next few centuries (slow downs appear in some of the IPCC models out to 2100).
A complete shut-down is possible (it has happened before, notably during the Younger Dryas), but it is hard to predict, as causes are not very well understood. But it seems unlikely to happen any time soon.


Does Earth's rotation cause sea levels to increase from east to west? Intuitively if the Earth were to rotate fast enough from west to east, the average sea level would be noticeably higher on the west edge of the oceans. Does Earth's rotation cause this effect in reality?

I ask as in Bill Bryson's book 'A Short History of Nearly Everything' on p.334 ch.18, he says

  The Pacific is about a foot and a half [~46cm] higher along its western edge - a consequence of the centrifugal force created by the Earth's spin.

No source is mentioned in the notes section and I found no exact source with a Google search. The closest I found was

Is sea level the same all across the ocean? - National Ocean Service

This is the change in sea level from 1993 to I assume 2019 (when the article was last updated). The data shows an increase in sea level on the Pacific's west side (and not the east side) but of course this is not exactly what Bryson stated in his book. Maybe there has been a mix up?

I ask as in Bill Bryson's book 'A Short History of Nearly Everything' on p.334 ch.18, he says

The Pacific is about a foot and a half [~46cm] higher along its western edge - a consequence of the centrifugal force created by the Earth's spin.

Bryson is right in the sense that in places there is a difference in height between the eastern Pacific and western Atlantic, at least in some places. He is however wrong about the magnitude of that height difference and wrong about the cause. From the Permanent Service for Mean Sea Level,

Sea level is about 20 cm higher on the Pacific side [of the Panama Canal] than the Atlantic due to the water being less dense on the Pacific side, on average, and due to the prevailing weather and ocean conditions. Such sea level differences are common across many short sections of land dividing ocean basins.
The 20 cm difference is determined by geodetic levelling from one side to the other. This levelling follows a 'level' surface which will be parallel to the geoid (see FAQ #1). The 20 cm difference at Panama is not unique. There are similar 'jumps' elsewhere e.g. Skagerrak, Indonesian straits.
If the canal was open sea and did not contain locks, i.e. if somehow a deep open cutting had been made rather than the canal system over the mountains, then there would be a current flowing from the Pacific to the Atlantic. An analogy, though imperfect because there are many other factors, is a comparison between Panama and the Drake Passage off the south tip of Chile, which has a west-east flow. (The flow in the Drake Passage is primarily wind-driven, but Pacific-Atlantic density must play some role.)


How do mountain springs get their water? I am curious how do mountain springs get their water. The water flowing from them eventually forms rivers.

Is it only from rain and snow? Or does water also come from underground-below the mountain (if so, then how does it "climb" to the spring which is at a high altitude)?

Ultimately, it comes from precipitation.  Ordinarily we think of rain as coming from low-level clouds, but Putkonen[1] has compiled rainfall data in the Himalayas showing significant rains up to several thousand meters altitude, covering the range where practically everyone lives.  It is this precipitation that fills the underground tables mentioned by Jean-Marie Prival in a comment to the question.

Such a source is subject to the effects of climate change, which accordingly has led to significant environmental issues.  See Ref [2].

References:

1.
Jaakko K. Putkonen, "Continuous Snow and Rain Data at 500 to 4400 m Altitude near Annapurna, Nepal, 1999–2001", Arctic, Antarctic, and Alpine Research, 36:2, 244-248 (2004)

2.
Sandeep Tambe, Ghanashyam Kharel, ML Arrawatia, Himanshu Kulkarni, Kaustubh Mahamuni, Anil K Ganeriwala,
"Reviving dying springs: climate change adaptation experiments from the Sikkim Himalaya",
Mountain Research and Development 32 (1), 62-72 (2012)


What is the difference between radiation balance and the global energy balance? Looking at two diagrams below, they seem to depict the same system. How are they different? Why one is a radiation balance model and the other a global energy balance model?

RADIATION BALANCE MODEL:

GLOBAL ENERGY BALANCE MODEL:

Radiation balance only account for energy transfers trough electromagnetic radiation. Something very useful for the Earth as a whole. As it is the only (or most important by far) way of energy exchange between the Earth and the outer space.

Energy balance in the other hand, account for energy transfers trough all possible processes, namely radiation, conduction, sensible heat, latent heat, convection, etc. That are very important to account for the energy transfers within the atmosphere and between it and the surface.

In this case your global energy balance includes evaporation and convection (thermals), that are forms of energy exchange not mediated by electromagnetic radiation.


Where on Earth is the magnetic field intensity stronger? Are there places on Earth that have a strong magnetic field other than the magnetic north and south poles?

Can living where (rare) earth magnetic ore is abundant provide a mini-magnetoshere?

If we consider only the magnetic field generated by natural sources, and not the ones generated by human activities. The general trend is that higher intensities of the magnetic field happen close to the magnetic poles. However, this is just a general trend. The southern hemisphere experiences the highest magnetic fields intensities, reaching over 65,000 nT, and this southern maximum matches fairly well with the south magnetic pole. In contrast, in the northern hemisphere, the maximum happens in Siberia, quite far from the north magnetic pole that is currently very close to the geographic north pole.

There are many models of Earth's magnetic field. You can find a comprehensive list at geomag.org. You can find the intensity output of NOAA's World Margentic Model for 2015, here. Shapefiles with the contours are available for 2018 here (as well as more maps), and the coordinates of north and south poles computed by the WMM model up to 2020 are available here. Putting together all the information for 2018, the map looks like this

The contour interval is 1000 nT, grid lines interval is 10°, and the green dots represent the south and north magnetic poles.

The maximum intensity contour in the northern hemisphere happens in Siberia with a value of 61,000 nT and the center of the contour is located roughly 3,100 km away from the magnetic north pole.

The maximum intensity contour in the southern hemisphere is between Australia and Antarctica, with a value of 67,000 nT and the center of the contour is located roughly 450 km away from the magnetic south pole.

So the answer is: Yes, there are. Maximum field intensity doesn't happen at the magnetic poles. Specially in the Northern hemisphere, the maximum intensity happens in Siberia, a few thousand kilometers away from the magnetic pole. The maximum intensity globally according to NOAA's WMM model is located in the southern hemisphere, approximately at 60° 15' S, 135° 52' E, about 450 km away from the south magnetic pole

The projection in the map above (geographic) generates a big distortion of the distances, the images below show the same information in polar stereographic projection:

Now, it is worth adding that the above information wouldn't be significantly modified if you consider natural magnetic anomalies due to magnetic crustal deposits. This is because magnetic anomalies are usually smaller than a few hundred nT, therefore the magnetic field intensity pattern is largely controlled by the internal magnetic field. Magnetic anomalies are not mapped over the whole world, but the World Digital Magnetic Anomaly Map, provides a pretty good estimate

However, these anomalies are measured  at an altitude of 5 km above mean sea level, and have a resolution of 3-arc-minute resolution (~5 km). Therefore, it doesn't rule out the existence of very strong and localized small scale anomalies, that might lead to large variations on the magnetic field intensity but over a very small area.
The maximum value within the World Digital Magnetic Anomaly Map dataset is 8570.78 nT, but even considering all anomalies, the largest field intensities remain within the same contour near the magnetic south pole.


How to open old GOES-1 satellite image files downloaded from NOAA CLASS This is the first time I have ordered satellite imagery via the NOAA CLASS system using the shopping cart, so I am a complete novice.

I have requested and downloaded old GOES-1 images from May 1979, but the problem is it seems the way in which the files are named perhaps and I don't know how to fix this, as it is affecting the file extension which creates something you subsequently can't open.

For example, the files I have downloaded (whether over ftp or www option) are called:

goes01.1979.149.1130.AREA_IR
goes01.1979.149.1130.AREA_VIS

And when you save them, it says you are saving a file with the '.AREA_IR' and '.AREA_VIS' file extension, which is of course not what I want, as how do you open it?

Now, under user preferences, there are only two options for these old images - AREA format or RAW format. So, I choose .raw format which I know I can open. I request another download and I get these two files for downloading:

goes01.1979.149.1200.a
goes01.1979.149.1200

and, this time it wants to download a '.a' file and a '.1200' file which is obviously not what it's supposed to be.

I have tried renaming the files (especially the second set) to no avail -- I have tried .raw on the end, and I saw they use the word dataset so I have even tried .tar and .tar.gz in case it might be an archive -- nothing works.

When you go into the details of your order, they do say it is .tar file initially, but I tried to download it by adding the .tar extension upon saving even, and still nothing -- won't open in archive software.

Has anyone encountered this? How do I use these files?

Unfortunately, the older weather satellite data is, the harder it is to read.
Perhaps NOAA's Weather and Climate Toolkit can open it.

The old stuff usually comes in tightly packed binary formats that may or may not be well documented (these satellites were designed to take pictures of clouds for weather forecasters to use, us future generations were more or less an afterthought).  Just to illustrate the difficulty: I've previously worked with data from the NOAA HIRS instrument from the late 1970s/early 1980s, and found that the headers contained a mixture of ASCII and EBCDIC information, and that some necessary calibration parameters for the thermistors on the on-board internal warm calibration target were simply lost, and that for some satellites, the available header documentation did not match what was actually in there, and I couldn't read most of the headers.  Other information useful for interpretation existed in the NOAA library, but was unavailable to me due to export restrictions (ITAR).

The imager on the first generation GOES satellites is the Visible-Infrared Spin Scan Radiometer (VISSR, flown on GOES-1–3 between 1975 and 1993.  A similar instrument with the same name has flown on several Japanese HIMAWARI GMS satellites between 1977 and 2000.

Pytroll is a series of Python packages to read and process satellite data.  It includes Satpy, which can read a large number of meteorological satellite imager data formats.  I think that anything that can be read by Satpy should be openable by the Satellite Information Familiarization Toolkit (SIFT), under development at the University of Wisconsin-Madison.

Unfortunately, I don't think Satpy has a reader for GOES VISSR (most focus is on current and future instruments), although there are plans for GMS VISSR (I don't know why this issue was closed).  Considering the similarity of the instruments, a reader for one should hopefully be similar to a reader for the other.  At least for GMS VISSR, file format documentation is available.  For GOES VISSR, some information appears retained at CEDA, but unfortunately that appears to be lacking in the detail you would need.

If you plan to develop a reading routine (you'd need to learn Python first if you don't know it already), do hop in to the Pytroll slack for advice.  There are also Pytroll workshops (normally twice a year) that are a great resource if you intend to work on a new satellite reader.

There might exist propriety software that can read this data, but unless you work at an employer that holds a license for such, that is going to be difficult to access.


What caused the Cretaceous uplift of the Harz mountains (Germany) What are the likely stresses that caused the uplift of the Harz mountains? Was the uplift connected to another orogeny, lithospheric-scale folding or a mantle process?

The intraplate compression responsible for this uplift has had a couple of explanations over the years; historically, it's been ascribed to Alpine collision, i.e. the collision of the Alpine orogen with the Europe. However Kley & Voight (2008) reviewed evidence and concluded it was the effect of Africa-Iberia-Europe convergence:

  ... the onset of intraplate contraction coincides with an important change in relative motion between the European and African plates. At ca. 90 Ma, Africa's SSE-directed sinistral transform motion relative to Europe changed to NE-directed convergence. This agrees well with the timing and kinematics of intraplate thrusting in central Europe. Structures of similar age and kinematics occurring in southern France, Spain, and North Africa suggest that the Late Cretaceous pulse of contraction was caused by pinching west-central Europe's thin lithosphere between Baltica and Africa. Only since the onset of N-directed thrusting in the Alps in Paleocene or Eocene time are the kinematics of the Alps and their European foreland compatible, indicating that mechanical coupling between Africa-Europe and the Adria microplate had been achieved.


Did a crater cause the break up of Gondwanaland & separate Australia from Antarctica In 2006 it was reported that the Largest Ever Killer Crater was found under ice in Antarctica. Gravity measurements taken by NASA's GRACE satellites indicate the crater is 250 million years old.

The size and location of the crater, apparently 480 km across, located in the Wilkes Land region of Eastern Antarctica, south of Australia have lead to suggestion the crater could have initiated the break up of Gondwanaland by creating the tectonic rift that pushed Australia northward.  The rift cuts directly through the crater, so the impact may have helped the rift to form. Australia split from the ancient Gondwana super continent about 100 million years ago.

Has the existence of the crater been verified and did it lead to the break up of Gondwanaland and Australia separating from Antarctica?

To clarify:

Your question is valid, although if you are referring to Dr. von Frese's words as paraphrased in this article, you may be conflating a potential "breakup initiation" with something like the "creation of a geologically weak area prone to rifting under extensional stress". I believe the thought that such a crater could have caused the beginnings of the rifting process was not entertained by Dr. von Frese himself. Instead, according to the article you cited, von Frese explains that Antarctica and Australia began rifting roughly 100 million years ago, and rifting just so happened to occur very near the proposed impact site. From the article:

  The rift cuts directly through the crater, so the impact may have helped the rift to form, von Frese said.

It's a little unclear, but I think von Frese is making the connection here that a crater of that size could have potentially created weak planes in the crust near the impact site, which would have directed extensional stress relief to a localized region, thus centralizing a rift locally. This is a plausible conclusion, but as far as I can tell, no evidence other than proximity has been found to support it.

To answer:

The existence of the crater has not been verified, and more recent research casts doubt about the validity of claims that the Wilkes Land structure is in fact an impact crater.

Furthermore, the date for the final breakup of Gondwana is fairly well established, and enough research has been conducted to construct extensive historical summaries of the time period. As stated by von Frese, most geologists put the start of rifting in the Wilkes Land region at about 100 million years ago, in the Cretaceous period.

If we allow the assumption that the crater is indeed caused by a bolide impact, most studies suggest an impact date near the time of the Permian-Triassic boundary, a period known for its multiple mass-extinctions, around 250 million years ago. That would leave roughly 70 million years between impact and Gondwana's very earliest rifting (~180 mya), which is a relatively significant amount of time by tectonic standards. As stated in the above reference, the current most accepted "method" of Gondwanan rifting is via mantle plumes forcing the continents apart from below.

Based solely on these two pieces of evidence, I'd feel relatively confident in putting forth that the breakup of Gondwana was not caused by a bolide impact. If the Wilkes Land structure is ever drilled, and shocked quartz or other impact indicators are found in the samples, I would want to revisit this answer to investigate what I'll call "Dr. von Frese's Planes of Weakness" claim more closely.


Why aren't seismic stations installed very deep underground so as to pre-warn from earthquakes? The velocity of p-waves emanating from earthquakes is in the range of 5-8 km/s (link)--let's assume it is 5 km/s. The earthquake depth is up to hundreds of kms deep underground (link)--let's assume it is 100 km.

That said, if a seismic station is installed at a depth of 50 km, and there are many of them in any given metropolitan area, then we can have a warning that is tens of seconds before the earthquake reaches the surface.

While I realize that drilling down to 50 kn is no easy task, I would have imagined that saving human life is well worth the efforts. Why hasn't this been done so far? Is it that such a short notice (10s of seconds) isn't worth it?

The simple answer is that you can't drill to 50 km depth.

The deepest holes ever drilled were to a little more than 12 km, one is named the Kola Superdeep Borehole in Russia, which was a scientific drilling project. The very few others were oil exploration boreholes.

Drilling that deep is extremely expensive and hard. If you go and ask anyone who ever worked on a drill rig, drilling the second 100 metres is always harder than the first 100 metres. And we're talking about kilometres here! There are several problems with drilling that deep. It's extremely hot down there, and the drilling equipment just breaks and stops working. You also need to pump cooling water in and pump out the stuff you're drilling and it gets harder with depth.

This is simply not feasible. Now let's say that you did somehow manage to drill a hole to that depth. How would you put monitoring equipment inside? That equipment has to sustain heat and pressure and still keep working, while being able to transmit whatever it's reading back to the surface. This is not going to happen, not at 50 or 10 km depth.

Another problem is that not all earthquakes are that deep. Some earthquakes originate near the surface, or just several km deep. Having a monitoring station down there isn't going to help. The 2011 Tohoku earthquake (the one that triggered the tsunami at Fukushima) was only 30 km deep. Same thing for the 2004 Indian Ocean earthquake.


Ozone layer and radiation absorption The ozone layer if compressed to a minimum on the earth's surface can absorb infrared radiation. How is it possible that the same molecule can absorb radiation of two different wavelength with changing altitude?

Ozone can indeed absorb UV and infrared radiation. The UV part, plays an important role in protecting us from harmful radiation, and the infrared part makes it an effective greenhouse gas.
All gases absorb/emit radiation at multiple different and discrete wavelengths. That's know since the early 19th century when the Fraunhofer lines where observed. The wavelengths can change depending on ionization and other factors. But in this case,I don't think there is any change in the absorption wavelengths between stratospheric and tropospheric ozone.

If you have information about such phenomena, please provide documentation. However, my guess is that in different situations studies might mention the absorption wavelengths that are relevant to the case, but that doesn't mean that it doesn't absorb in other wavelengths too.

In particular, close to the Earth's surface there is plenty of infrared radiation, and very little UV radiation. Therefore, ozone might absorb more energy in the infrared. The oposite happen in the stratosphere, where it probably absorbs more energy in the UV bands.

UV absorption bands are the most known for Ozone, but as I said it has infrared absorption bands too. You can see those bands in the following infrared spectrum obtained from NIST:


Could a reported rainfall pH of 3.1 actually be realistic? In this Chemistry question Is there any reason to fear personal exposure to rain with a pH of 3.1? I haven't gotten any answer, but there was some discussion about the reality of the measurement.

So I'll ask here, is a sustained rainfall with a pH of roughy 3.1 possible on Earth? Of course it would have to be related to some serious sources of pollution - perhaps intensive coal burning over a large geographic region. I say 'sustained' to rule out any fluke or highly unusual situations. Could I really fill a plastic bucket with a substantial amount of pH 3.1 water by putting it outdoors, under the sky, in the rain, in the right place on Earth?

Oh, for this question I'd like to exclude unusual situations related to volcanic eruptions as well.

A quick literature search seems to confirm Gordons estimation, even at the scale of a whole bucket:

  [T]he annual mean pH, based upon
  samples collected weekly during 1970-1971 and weighted proportionally to
  the amount of water and pH during each period of precipitation, was 4.03
  at the Hubbard Brook Experimental Forest, New Hampshire; 3.98 at Ithaca,
  New York; 3.91 at Aurora, New York; and 4.02 at Geneva, New York. Measurements
  on individual rainstorms frequently showed values between pH 3
  and 4 at all of these locations. Data from the National Center for Atmospheric
  Research included precipitation pH values as low as 2.1 in the northeastern
  United States during November 1964.

Patel, C. K. N., E. G. Burkhardt, and C. A. Lambert. "Acid rain: a serious regional environmental problem." Science 184 (1974): 1176-1179.


Are the storm cones introduced by Robert Fitzroy still in use? In 1860 or so, following the tragic wreck of the Royal Charter with the loss of over 400 lives, storm cones were installed in many UK ports, under the direction of Admiral Fitzroy, head of the government's forerunner of the modern Meteorological Office, to warn mariners of expected gales. My question is, please, are these storm cones still in use?

A page in the book Come Rain or Shine, A Weather Miscellany states that the cones were discontinued on June 1, 1984, due to their being superseded by radio broadcasts and other methods.


Is increase in atmospheric $\mathrm{CO}_2$ concentration affecting Earth's atmospheric pressure? It's well known that the $\mathrm{CO}_2$ levels around the world are increasing, leading to an increase in overall surface temperature, etc.

But I'm wondering, are these gases (or the effects from these gases) increasing the global atmospheric pressure to any great degree, or is the atmospheric composition changing without any major change to air pressure levels, compared to centuries or millennia ago?

The air in the atmosphere is a fluid. The pressure exerted by a fluid on a horizontal surface can be calculated using the formula.

$$ P = \rho\,\mathrm{g}\, h $$

Where:

$P$ is pressure
$\rho$ is the density of the fluid
$\mathrm{g}$ is the acceleration due to gravity
$h$ is the height of the fluid

The acceleration due to gravity is a constant and the height of atmosphere can be considered constant. That leaves only the density of the air in the  atmosphere as the only variable that will affect pressure on the surface of the Earth, in this situation.

The amount of carbon dioxide in the atmosphere is around 400 parts per million — a very small proportion.

Air density varies according to temperature and pressure but is within the range of $1.146$ to $1.422\ \mathrm{kg/m}^3$. By comparison, water has a density of $1000\ \mathrm{kg/m}^3$.

If the quantity of carbon dioxide were to increase, even tenfold, it would have a negligible affect on the density of the air and thus a negligible affect on the atmospheric pressure on the surface of the Earth. Its effect on temperature is another matter.

Edit

Answer to the additional question: Can you expound on what effect the increase in temperature will have on pressure?

The relationship between pressure, temperature and volume for gases is given by the universal gas law which states,

$$ PV = m\, \mathrm{R}\, T $$

Where:

$P$ is pressure
$V$ is volume
$m$ is mass
$\mathrm{R}$ is the universal gas constant
$T$ is temperature

Rearranging the equation,

$$ P = \frac{m\mathrm{R}T}{V} $$

When considering the affect of temperature on atmospheric pressure, $\mathrm{R}$ is already a constant and the mass and volume of the atmosphere can be considered to be constant because any changes due to increased $\ce{CO_2}$ will be exceedingly small and can be regarded as being negligible.

Consequently $m\mathrm{R}/V$ is a constant $\mathrm{k}$ and the equation becomes,

$$ P = \mathrm{k}T $$

The Kelvin temperature scale, used in the equation, is an extrapolation of the Celsius temperature scale, thus a rise in temperature of $1^\circ\mathrm{C}$ ($1\ \mathrm{K}$) will increase atmospheric pressure by $1\ \mathrm{pascal}$.

The average atmospheric pressure is $101\,325\ \mathrm{Pa}$. Assuming a very bad case scenario of a rise of $10^\circ\mathrm{C}$, the pressure would increase $10\ \mathrm{Pa}$, or $0.0099\%$, which is insignificant.

Weather reports report atmospheric pressure in units of hectopascals ($\mathrm{hPa}$). A pressure of $101\,325\ \mathrm{Pa}$ is $1013.25\ \mathrm{hPa}$. A rise of $10\ \mathrm{Pa}$ is the same as $0.1\ \mathrm{hPa}$. Atmospheric pressures vary between $890\ \mathrm{hPa}$ and $1090\ \mathrm{hPa}$.


Is it possible for a natural fluorescent mineral to glow from the sun's rays? I have been searching certain fluorescent minerals, such as Andersonite, and all websites are saying how the mineral will glow if exposed to Ultraviolet light. Does enough ultraviolet light come through the atmosphere (from the sun), to make any natural minerals actually glow, and to keep glowing for a time if the light was removed? If there is not enough UV light, or if no such mineral exists, would it be possible for such a mineral to exist?

The lifetime of a fluorescence excited state is on the nanosecond to microsecond time scale.  So once the excitation source light is removed, the emission of light will stop within microseconds.

Note that fluorescence is distinct from phosphoresence, and phosphorescence can involve longer lifetime excited states.

Spectroscopic Characterization of the Uranium Carbonate Andersonite provides quantitative information on fluorescence lifetimes for Andersonite, and lifetimes are in the microsecond range.

Regarding phosphorescence, see Phosphorescence; or, The emission of light by minerals, plants, and animals (1862):

  SEVERAL substances manifest the strange property  of emitting light
  when they are placed in darkness,  after having been exposed for some
  time to the  direct rays of the sun. In some cases a very short
  exposure to sunlight is sufficient to excite the  manifestation of
  this remarkable property, and in  others the direct rays of the sun
  are not necessary :  it suffices that the substance experimented upon
  be exposed to the dull light of a cloudy day. To  this phenomenon the
  denomination of Phosphores-  cence after insolation has been given.

  ' The substances which possess this property in  the highest degree
  are the Bologna stone, or solar  phosphorus, certain varieties of
  fluor-spar and  carbonate of lime, some fossils, calcined shells or
  pearls, phosphate of lime, arseniate of lime, etc.  Many diamonds
  shine with brilliancy in the dark  if they have previously undergone
  an exposure of  some seconds' duration only to solar light. But  no
  substance surpasses in this respect sulphuret  of barium.

  It is now a long time since the cobbler of Bologna,,  in Italy,
  astonished and amused his friends with a  peculiar substance since
  known as Bologna phosphorus, Bologna stone, or Solar phosphorus,
  which  shines brightly in the dark after having been placed  in the
  sunlight for some time. This substance is  sulphuret of barium. The
  cobbler prepared it by  heating red-hot with charcoal a piece of
  sulphate  of baryta, or Barytine, (Fig. I,) a stone which he...


Is the continent with Australia in it Oceania or Australia? I am making a quiz and I want to know whether Australia or Oceania is the continent? I have searched it on Google but I can't find an answer.

Partly, it depends on where you got educated. In many countries of Europe, Oceania is the continent. Calling the continent Australia is pretty much considered "English-centric". The reasoning for calling it Oceania is that Australia is only part of the continent. The extend of the mainland during the ice ages included part of today's Indonesia and Papua-New Guinea. While calling it Australia makes some sense and it is the largest part of the continent, in a sense it is like if we were to call Asia, Russia.

Source: Wikipedia (Maximilian Dörrbecker (Chumwa) - Self made, using this map for the background, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=7382691)


Similarities between grand circulation solvers and mantle convection solvers My impression is that both ocean grand circulation models (e.g. MITgcm), and Mantle Convection models (e.g. CitcomS), both use Navier-Stoke's as the governing equation. What are the other major similarities between these two types of models?

Should there be more shared between these two modeling communities since they both rely on fluid dynamics?

Edit: For those wondering why this might be important: You can use mantle convection to calculate dynamic topography, and then couple it with heatflow models to predict sea level rise. Of course, you also need to couple that with glacial melting dynamics and GCMs. See Muller et al., 2008 for more information. I know there are a few geodynamicsts now working on this problem in general, but no substantial work has been published . (May 2015)

Disclaimer: This is a partial answer given that my background is modeling of the ocean. I hope that some mantle convection modelers can complement this answer.

The question is good but the answer is complex. The short answer is:

No, they are not the same. Simply because computationally it would not make sense.

I will try my best to break it apart and make it as concise as possible.

Preface

As many people have pointed out scales are key. The environmental fluid dynamics problems we try to solve range enormous scales. However, every single motion is described by the Navier-Stokes (NS) equation, from the simplest flow you can think of all the way to the most complex - that includes turbulence (the continuum hypothesis says that the NS equations are valid when the Knudsen number $K_n \ll 1$).

Take a look at the chart below for oceanic processes alone. Temporal scales span 10 orders of magnitude, while spatial scales span 12 orders of magnitude. Presumably mantle solvers would extend the upper bounds on each of these scales.

The question you ask is specifically regarding oceanic grand circulation (OGC) models and mantle convection (MC) models. So according to the chart below, out of all oceanic models, the OGC and the MC models are the closest as far as temporal scales and spatial scales go.

The complexity of the Navier-Stokes equations and the difficulty in solving them

The Navier-Stokes system can be classified as a hybrid elliptic-hyperbolic type for steady flows and a hybrid parabolic-hyperbolic type for unsteady flows (the hyperbolic character comes from the continuity equation).

Where the nature of the equations say the following about each one and their respective numerical difficulties:

Hyperbolic nature is associated with wave phenomena and advective transport:

Fast waves lead to numerical stability restrictions
Nonlinear part of NS is hyperbolic ($\mathbf{u} \cdot \nabla \mathbf{u}$), which is the part of the equation that leads to turbulence.
Possibly one of the most difficult aspect of CFD is the propagation of sharp density fronts which are hyperbolic.

Parabolic nature is associated with diffusion and mass transport:

Boundary layers are governed by parabolic phenomena and are very thin compared to the environment that drives it. Notice the large scale disparity and associated numerical difficulty.
Turbulence, can be modeled from a parabolic perspective and this typically results in stability concerns on the numerical method employed.

Elliptic nature implies instantaneous propagation of information:

For environmental fluid dynamics, the nonhydrostatic pressure is of elliptic nature.
Although, theoretically, any disturbance propagates at infinite speed throughout the domain, numerical iteration sets a finite speed at which information can propagate.
Non-hydrostatic solvers have to invert a Poisson equation which is very computationally
expen  sive. In general, for the nonhydrostatic pressure, the 2-d problem requires the solution of a pentadiagonal, while the 3-d problem requires the solution of a
septadiagonal (7 diagonals) (not all near the main diagonal!).

Scales and numerical solvers

So as one can see by now, solving the NS equations numerically is not a trivial matter. Numerical solvers must face concerns regarding accuracy, stability and consistency, which pose constraints on the timestep and grid resolution that one can employ. See this answer regarding different approaches to numerical solvers. Scales are important for numerical solvers because of the nature of the system of the NS equations (described above) and the analytical mathematical techniques available to us to transcribe those equations to computational mathematical language. As it stands, it is impossible to resolve all temporal and spatial scales, so modelers resort to specific techniques (solvers) that apply to the problem (the scales) that they are interested in.

Conclusion

From their website:

  The MITgcm (MIT General Circulation Model) is a numerical model
  designed for study of the atmosphere, ocean, and climate. Its
  non-hydrostatic formulation enables it to simulate fluid phenomena
  over a wide range of scales; its adjoint capability enables it to be
  applied to parameter and state estimation problems. By employing fluid
  isomorphisms, one hydrodynamical kernel can be used to simulate flow
  in both the atmosphere and ocean.

and

  CitcomS is a finite element code designed to solve compressible
  thermochemical convection problems relevant to Earth's mantle.

My guess is they both use different numerical techniques to solve different versions of the Navier-Stokes equations that make the most sense given the scales of the problem that each one aims to resolve.


Can the dew point temperature be more than drybulb temperature? I am extracting data from WRF model output for a specific area. The area I am extracting data for is 5000m above mean sea level. When plotting on a graph, I found that the dew point temperature is higher than the dry bulb temperature.

Is it possible that the dew point can go higher than the dry bulb? If yes, what is the inference of this phenomenon? Or can I simply assume that WRF could not calculate temperature values properly for this hill station?

Dew point gives an indication of the moisture content of air; it is the temperature at which air can no longer hold water vapour.

The following graph shows the relations of dew point to air temperature (dry bulb) for various levels of humidity.

For humidity less than 100 percent, the air temperature is always higher than the dew point temperature and for a humidity of 100 percent air temperature equals the dew point temperature.

The dew point cannot be higher than the dry bulb temperature, it can only be lower of equal to it.


How does soil redox potential affect the rate of denitrification? Denitrification requires low oxygen conditions as wells as organic carbon.
Are reduced soils (e.g gleysols) more likely to have higher denitrification rates because they have low oxygen levels?

Denitrification requires anoxic conditions, organic matter, and NO3-.

Gleysols are anoxic soils formed in wetlands. Waterlogged wetland soils are generally both anaerobic and high in organic matter. For a given concentration of NO3-, denitrification rates should be higher in Gleysols than similar soils that are aerobic soils (because there will be less organic substrate and less anaerobic habitat).

Notably, even in aerobic soils, denitrification can occur within anaerobic microsites.

references:

Bedard-Haughn 2010. Prairie Wetland Soils in Prairie Soils and Crops Journal (pdf)
Schlesinger and Bernhardt 2013 Biogeochemistry 3rd Edition p 205-208


Golden and red colored light even after sunset I heard about the golden hour, but yesterday I saw golden and red colored patches in the sky even after sunset. Why does it happen? And I would like to know more about the science behind the golden hour.

This is a result of Rayleigh scattering, the same reason the sky is blue.  As the sun sets the optical path for a photon passing through the atmosphere to your eye  increases.  Because of this increased distance through the atmosphere, more scattering occurs and the shorter wavelengths are scattered away, leaving the longer wavelengths.  This results in light that is reaching your eye tending toward red and the yellow to orange and gold hues are produced on the way to red.

The reason you can still see this persist after sunset is because the sun below the horizon can still reach you through scattering though clouds can enhance this effect (because clouds are good at scattering all visible wavelengths and clouds you can see can be illuminated by a sun you cannot see).  This is the same principle as above, with the addition of the scattering by the cloud.  You'll have Rayleigh scattering on the way to the cloud through the atmosphere, uniform scattering off the cloud and then more Rayleigh scattering between the cloud and your eye.  The longer these distances become, the more red the light reaching your eye has become, and thus the sky will take on the reddening hue (with the yellow/orange/gold colors in the transition to red).


What was the highest temperature ever recorded on the surface of Earth? The article entitled "54 Celsius degrees in Iran, the highest temperature ever recorded?" says 56,6 Celsius may be the highest temperature ever recorded, in Death Valley, California, and it also mentions that Iran's heat index peaked at 61,2 Celsius in the event the story was about.

I ask this question because several cities in my province in Argentina are registering heat indexes of over 60 Celsius, with a maximum in the center of Santa Fe city of 65,7° Celsius.

So what was the highest temperature ever recorded on the surface of the Earth?

The record the article is referring about seems to be the same as registered at Guiness World Records:

  On 13 September 2012 the World Meteorological Organisation
  disqualified the record for the highest recorded temperature, exactly
  90 years after it had been established at El Azizia, Libya, with a
  measurement of 58°C. The official highest recorded temperature is now
  56.7°C (134°F), which was measured on 10 July 1913 at Greenland Ranch, Death Valley, California, USA.

Those records are usually well researched, and in this case it matches what is reported by the WMO. Since 2007, the WMO Commission for Climatology (CCl) has maintained the Archive of World Weather and Climate Extremes. In that archive, the same record is reported as the current highest temperature ever recorded:

More details about the record are described here.
The official WMO press release about the invalidation of the 1922 El Azizia record can be found here.

It is surprising however, that with most the hottest years on record happening in the last few decades, the maximum recorded temperature is still from 1913.

Some people have questioned the reliability of those old measurements. More recent and much more reliable measurements seem to top-up at about 54.0°C as pointed out by a very interesting article brought up by @Plutor in the comments.

Note that you are mixing temperature and heat index in your question. Make sure you understand the difference.

PS: "Greenland" Ranch... a rather sarcastic name for such a place.

Photograph of old Greenland Ranch Station, California, USA (source)


How were smaller reptiles/mammals more successful at surviving the KT event than larger dinosaurs? Last night, I was watching this programme on TV The Real T Rex where the presenter pointed out that smaller reptiles (crocodilians and mammals) "somehow managed" to survive the KT extinction event that wiped out the larger dinosaurs.

The survival of the smaller animals wasn't a subject of the programme, so this wasn't explored further.

But this got me to thinking...  What environmental/climatic factors could have promoted the complete extinction of the larger air/land/sea animals but allowed smaller species to survive?

It mostly has to do with three factors, numbers, fecundity, and behavior. Let's start with the last, certain behaviors that increase your chances of surviving are far more likely in smaller animals things like burrowing, and hibernation. They are also more likely to be generalists able to eat almost anything, specialization is a death sentence during a major environmental change. They also require less total amounts of food as individuals, it is far easier for a rat to find enough food to survive in a wasteland than an elephant, This is also true in comparing cold-blooded vs warm-blooded animals.

Second you have numbers, there are several billion rats in NYC alone, even with the total destruction of the city it is very easy for a some rats to happen to be lucky enough to survive, small animals will die in larger numbers but there are so many of them they are more likely to have some survive. They literally have the law of large numbers in their favor.

Last is reproduction, size is connected to reproduction, an elephant reproduces once every two years under ideal conditions, while a rat can breed every 24 days, so even if a few elephants do survive they repopulate so slowly they may never recover and some other minor event may finish them off.

So if you combine these not only are small animals more likely to survive they can recover far faster than most large animals, so all things being equal you should expect small animals to be better at surviving and diversifying after a event.


Total CO2 is not constant? I've got a friend who is a climate change sceptic.

He argues that because all the CO2 in fossil fuels originally came from the earth's atmosphere. Then there can't be a problem releasing the CO2  back into the same atmosphere.

Intuitively it seems obvious to me that the quantities CO2 was stored up over a long time and now is being released back into the atmosphere is just a few short decades which is causing problems but his counter is that the earth is a closed system and so the total amount of carbon CO2 is constant. This part I'm less sure on but I have a feeling he must be wrong on that too.

Can someone please explain where the flaw is his logic is? I want to debunk this in as scientifically accurate as way as possible.

First of all, earth doesn't have the same atmosphere it had, back when dinosaurs walked the earth, when most of current carbon-deposits formed. Some atmospheres earth had would even be toxic to humans. So, you're right, changing the atmosphere at the speed we're doing it is the problem, not the change in general.

Second, yes, earth is a rather closed system (with minor leaks, but anyway). Still, the timescale is important.

Let's go with a simple allegory:

Say, your friend had a pickup-truck (sorry, in my mind deniers all drive SUV or pickup^^). He uses it to transport a lot of material, e.g. paving stones. He knows, his truck is able to transport the total amount of stones (because he tried in the past, or because the specifications say so, or because someone told him, doesn't matter - like we know that earth's atmosphere held a lot more CO2 back in the day).

Is he going to just dump the whole load at once from 2 m height into the back of his truck? I doubt so, because that would at least put some dents in the truck, or might even break the springs or an axle.

He'd pack the stones there manually and use enough padding to make sure nothing gets damaged or slips during the transport.

Currently we're dumping the stones all at once - and we'll surely break the vehicle, if we really continue. Earth, like the truck, needs to adapt to changes. And, as we know, geological timescales are a lot longer than we can truly observe - thus the current changes, though stretching over several generations, are way too fast for earth to really adapt.

Third: While earth is a closed system, states within a closed system may change. Say, you have a terrarium with some mice and a lot of wood. Then you burn the wood. The mice might survive the fire, but in the end will suffocate, since there is a lot more CO2 in their atmosphere now.

So, yes, releasing trapped carbon from fossile fuels and whatnot to the atmosphere doesn't change the overall mass of system earth. But it changes the state of the system - and we are depending on the current state of the system.

Also - I know, this is not scientifically - say we are wrong when it comes to greenhouse gasses, and he is right. What if we undertook a lot of effort to not to produce them, to clean our environment, to create less waste? We'd wake up one morning and be "Dang, we made our planet worth living on again, how could we?!" - Or, as one of my professors put it: "Would you get on a plane when there is a 10 % chance, the plane is going to crash?"


Could a waterfall lashing onto a road lead to a landslide? Here is a video of a waterfall lashing on to a mountain road, with vehicles driving under it.

https://youtu.be/cHaguj--YBc

There appears to be a big hole carved out right next to the road, possibly by the force of the waterfall.

Is this a ticking time bomb for a landslide?

Potentially, a landslide could occur. Whether it would be a minor slip or a major fall depends on the geological conditions at the site, the force of the water and the duration that the site is impacted by the water.

In the video in question, the rock face above the road appears competent, but there are not guarantees. The main issue would be is the water undermining the road which could cause a slip and the road to slide.

The more loose the geological material is, the easier it is to dislodge it. Once one item moves a chain of events can occur where additional items are dislodged and a slide occurs.

In addition to high pressure water dislodging material, water acts as a lubricant, making it easier for rocks and regolith to be dislodged.

To minimise the potential for a slide to occur in such a situation, the surface of the road would need to be sealed very well and a very good drainage system installed that would move the water away from the road and the slope below the road


What is the age of the earliest traces of life on Earth? In the article Oldest rocks, earliest life, heaviest impacts, and the
Hadean–Archaean transition (Moorbath, 2005), the author states (based on previous referenced research) that the $\ce{^13C}$ depletion previously stated as being a biotracer of the presence of early life in the metamorphosed sedimentary Archaean aged (~3.8 billion year old) rocks found in Isua, Greenland is disputed, by what the author states as being a result of

  serious metamorphic
  and tectonic complications for a biogenic
  interpretation.

Hence, the presence of the traces of very early life at that location (and age) are not confirmed.

Thus, what is the age of the earliest traces of life on Earth?

Fossils are our strongest, and to most people most accessible, evidence of the great age of life on earth. The fossils in the Burgess Shale are clearly the imprints of critters, but are a mere 505 million years old. The oldest cyanobacteria-like fossils known are nearly 3.5 billion years old, among the oldest fossils currently known. There is Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks, but requires knowledge of isotopic chemistry to understand (or dispute.) Life on earth originated before 3.5 billion years ago.


Pressure as a function of altitude above 11 km I need to calculate the force that causes a weather balloon with a specific volume to rise. Having searched for quite a few hours, I found the needed formula that can be used to calculate the pressure at a certain altitude. (surprisingly, the formula given on the German Wikipedia gives better values than that from the English one )

This is needed to get the density of the air, which can then be used with Archimedes' principle to get the buoyancy force of the balloon a that height.

However, it is stated that the formula only returns valid values for altitudes up to 11 km. Is there a way to calculate the air pressure at a higher altitude?

Those formulas are based on an assumption that the pressure is hydrostatic and the ideal gas law. The example given is limited to 11km but uses the tables from the U.S. Standard Atmosphere which actually go up to $1000$ km. Starting at Page 58 one can find values for pressure density and temperature above 11km.


How sustainable is timber housing? Recently I watch a video on which they made a pretty impressively large building complex for housing out of timber. And they were saying that timber is sustainable compared to concrete and such.  From the outset this seems pretty straight forward, trees grow back so long you don't do anything terrible to the ground the grow on (like salt it or build a shopping mall), and concretes components (ie. the stones and calcium oxide. the water does evaporate) does not. However thinking a little harder I know that plants need phosphorous to grow, and currently there is a shortage of of phosphorous. If we are using tress to build our skyscrapers, wouldn't they be locking away our supply of phosphorous for our food and the world's ecosystem? Therefore, is using timber really that sustainable?

that all said it'll probably be better than concrete and steel, and nothing probably perfectly sustainable.

Building with timber is more sustainable than building with concrete at least in terms of the production of green house gases.  A timber building is using a raw material, trees, that have been sequestering carbon till they are cut.   Cement, or concrete, on the other hand is made by cooking off carbon dioxide from the calcium carbonate, limestone, to produce the lime which makes up a large part of the concrete.  In the production of lime you have CO2 released from the limestone and from the fuels used to heat the limestone, see Lime in Wikipedia.  In addition the timber panels are significantly lighter than the cement components which should also make the timber construction more sustainable.

Most trees used for timber production are grown in sites that are not generally ideal for other types of agriculture, though this is a gross generalization.  They get their phosphorous through local sources, primarily the soil, so forest growth wouldn't have an impact on the phosphorous used for agricultural processes.

The following quote from the North Carolina State University project site summarizes the overall impact on timber construction.  It is important to note that until the advent of CLT, cross laminated timber, it was effectively impossible to build larger structures out of wood.

  CLT paneling is also thermally efficient, requiring 1/3 the heating and cooling energy compared to other traditional building systems. CLT paneling is also beneficial to the environment.  Wood is the only major building material that grows naturally and is renewable, CLT also outperforms steel and concrete in terms of embodied energy required to make the product. It also has a less of an effect on air pollution (stores carbon) and water pollution. CLT Panels USA


How to install ESMF and ESMFPy in Ubuntu using gfortran, gcc, python? I am trying to regrid some of my latitude-longitude grid files to tripolar ocean grid and found that ESMF can be useful. However, I am finding it hard to install the same.

First download the esmf tar file from http://www.earthsystemmodeling.org/esmf_releases/public/ESMF_7_1_0r/reg/ESMF_Framework_Down.html

Then install netcdf library and gfortran compiler using

sudo apt-get install git tcsh pkg-config
sudo apt-get install gfortran
sudo apt-get install netcdf-bin libnetcdf-dev libnetcdff-dev
sudo apt-get install openmpi-bin libopenmpi-dev
sudo apt-get install libnetcdff-dev

Once you have the netcdf library and gfortran compiler in your /usr/local/lib and /usr/local/include You can check this also, login as root using

sudo -i

Then define the following environment variables

cd path_of_esmf_dir
export ESMF_DIR=path_of_esmf_dir
export ESMF_INSTALL_PREFIX=/usr/local/esmf
export ESMF_OS=Linux
export ESMF_NETCDF="local"
export ESMF_COMM=mpiuni
export ESMF_F90COMPILER=gfortran
export ESMF_CXXCOMPILER=g++
export ESMF_TESTEXHAUSTIVE=on
export ESMF_TESTSHAREDOBJ=on
export ESMF_NETCDF_INCLUDE=/usr/local/include
export ESMF_NETCDF_LIBS="-lnetcdf -lnetcdff"
export ESMF_NETCDF_LIBPATH=/usr/local/lib
export ESMF_BOPT=O3

Then run the following syntax to make the library ESMF

make all
make install
make installcheck

Now to install the ESMF python library

cd path_to_esmf_dir/addon/ESMpy/
python setup.py build --ESMFMKFILE=/usr/local/esmf/lib/libO3/Linux.gfortran.64.mpiuni.default/esmf.mk
python setup.py install

You can check the installation by

$ python
>>> import ESMF

ESMF python library has got limited features as compared to the ESMF library. Hence it is better to use ESMF directly.


Could the Earth's core lose its heat? Will all the drilling and digging to use the Earth's natural heat as geothermal energy affect the Earth's core, causing it to cool down?

If so, would it result in an ice age?  If not, how does the Earth's core retain its heat?

Part 1, see Neos answer.  Earth will lose its heat no matter what we do, and our extraction of geothermal energy is insignificant (Wikipedia quotes a BP figure of 11.4 GW electrical, 28 GW heating).

To answer part 2 of your question: if the Earth's core loses its heat, this will not have a major direct impact on climate.  Internal heat generation is estimated by Davies and Davies (2010) to be roughly 47 TW.  With a surface area of 5.1 × 1014 m2, this translates to roughly 0.1 W/m2.  This can be compared to the other flows in the climate system, illustrated by Trenberth and Fasullo, 2012:

—Trenberth, Kevin E., and John T. Fasullo. "Tracking Earth’s energy: From El Niño to global warming." Surveys in geophysics 33, no. 3-4 (2012): 413-426.  Weblink

So, from a climate perspective, internal heat generation is not important.  See also this post on skepticalscience.

However, we might lose our atmosphere, which would have inconvenient consequences.  An ice age would be the least of our worries.  A subsequent question would be: (How long) would Earth's atmosphere last without a global magnetic field?  That is a different question and I'm not sure if we really know the answer.


How do the pros measure humidity? I have used a wet/dry bulb setup to estimate humidity, and it appears that the Argentinian meteorological service uses one in Antarctica as well.

Wikipedia sez:

  Humidity measurement is among the more difficult problems in basic metrology. According to the WMO Guide, "The achievable accuracies [for humidity determination] listed in the table refer to good quality instruments that are well operated and maintained. In practice, these are not easy to achieve." ...Hygrometers must be calibrated in air, which is a much less effective heat transfer medium than is water, and many types are subject to drift so need regular recalibration. A further difficulty is that most hygrometers sense relative humidity rather than the absolute amount of water present...

Question: In practice, how do weather reporting stations measure humidity? Is there a difference between remote locations and those where people visit regularly? Does there tend to be a difference between instruments used in arctic and tropical conditions?

The WMO report Instruments and Methods of Observation has a chapter on Measurement of humidity and a separate chapter on Measurement of upper-air pressure, temperature, humidity. The first deals with instruments used for surface measurements. The second deals with instruments used for measuring vertical profiles, which have to deal with a larger range of temperatures and pressures.

For the surface instruments they list:

Gravimetric: take an air sample, extract all the water and weigh it (typically  used for calibration);
Chilled mirror: dewpoint or frostpoint: used for observations and for calibration;
Salt-solution: matching vapour pressure of a salt solution to atmospheric vapour pressure: used in automated weather stations;
Psychrometric: comparing wet or ice bulb temperature with actual temperature - used in observations and calibration;
Sorption methods: using hair or an alternative which stretches when wet, or using a material with a electrical resistance or capacitance that changes when wet.

In other words, the professionals use a lot of different methods.


Is there enough water to cover the surface of a topographically normalized earth? Is there enough water in the oceans, ice caps, rivers and streams to cover a completely flattened earth, in proportional to land volume and water volume?

Here is a very simplistic approximation:
The total volume of the oceans (no lakes, rivers, water vapor) is around $1.3\ 10^9$ cubic kilometers. The surface area of Earth is around $5\ 10^8$ square kilometers. Dividing the volume by the area, we get a depth of 2.5 kilometers. The fresh water contribution is about 3% of the volume of salt water.

In reality, other factors such as the fact that Earth is not spherical, density changes, and that the water will be acted upon by tidal forces and other interactions, will make the distribution uneven.


Great Pacific Garbage Patch Equilibrium Points I was watching the science channel yesterday and the program mentioned the Great Pacific Garbage rim. I was struck by the illustration (and pretty much every subsequent animation/picture I've seen now has the same basic illustration) below:

Unless I'm not understanding something, the garbage swirls around in a huge  closed trajectory and encloses two sinks ( the colorful swirly things; one on the left and one on the right). This isn't physically possible though, with the perfectly reasonable assumption that the tidal force field is continuously differentiable. Any closed curve has to enclose equilibrium points who's indices add to $+1$, but a sink has an index of $+1$ so this curve encloses a total of $+2$. There would have to be at least one other equilibrium point inside the closed trajectory that had an index of $-1$, so something like a saddle node:

But I can't find any illustrations showing any other equilibrium points other than these two. Does anyone know what they are, or perhaps if I'm not understanding something?

Theoretically, I agree that there should be one instable equilibrium point between the two stable equilibrium points when we have a 2D current field. However, there are some additional components of the problem:

Ocean currents are not 2D but 3D currents. Considering only the sea surface might lets field lines disappear.
The wind has an additional forcing. This is not true for all items and the wind already affects the ocean currents. However, litter items which are partly above the sea surface experience an additional wind forcing (see e.g. Yoon et al., 2010)
Ocean currents are not time independent and equilibrium points may undergo a seasonal multi-annual cycling
Accumulation zones are not necessarily stable equilibrium points but the residence time of the marine litter items in the named regions just needs to be sufficient long.
The gyres are macroscopic accumulation regions. Thus, if we have regions with a higher density of particle trajectories and lower particles velocities we could identify these regions as accumulation regions from a macroscopic perspective.

About item three (Ocean currents are not time independent) I am not completely sure, but I think to remember an animation or plots in a publication which showed seasonal variations between the both garbage patches you showed.

As far as I remember the publications on that topic of global transport modeling of marine litter correctly, the eastern North Pacific Garbage patch is the actual accumulation region. It has a long tail towards west. Howell et al. (2012) writes about the North Pacific Gyre and plastic debris accumulation within it. I did not have time to read it in detail.

For further reading it might be interesting to look into these publications:

Eriksen et al., 2014. doi: 10.1371/journal.pone.0111913
Howell et al., 2012. doi: 10.1016/j.marpolbul.2011.04.034
Lebreton et al., 2012. doi: 10.1016/j.marpolbul.2011.10.027
Martinez et al., 2009. doi: 10.1016/j.marpolbul.2009.04.022
Maximenko et al., 2012. doi: 10.1016/j.marpolbul.2011.04.016
Yoon et al., 2010. doi: 10.1016/j.marpolbul.2009.09.033


Is there any explanation for the large amount of sea ice around Antarctica in 2014? As can be seen from the below data, for the past year or so (2014), sea ice surrounding Antarctica has been well above normal.  Currently, Antarctic sea ice is at an all-time record high for this time of year, 1,344,000 square kilometers above normal (or about the size of Spain, France and Germany put together).

Is there any explanation for such an extreme excess of sea ice around Antarctica recently?

Source of data is the US National Snow and Ice Data Center sea ice news for April 2014 (for the upper graph) and University of Illinois's "The Cryosphere Today" (for the lower graph).

In the above link, the National Snow and Ice Data Center states "Antarctic sea ice extent for April 2014 reached 9.00 million square kilometers (3.47 million square miles), the largest ice extent on record by a significant margin."

Update 6/30/2014 :

Now the anomalously high southern sea ice has reached a record level for any time of year, at more than 2 million square kilometers above normal.

Antarctic sea ice extent for April 2014 reached 9.00 million square kilometers (3.47 million square miles), the largest ice extent on record by a significant margin.

  Is there any explanation for such an extreme excess of sea ice around Antarctica recently?

I'll give four separate answers:

It's not as significant an increase as you think.
The Interdecadal Pacific Oscillation is strongly in its negative phase.
The Southern Annular Mode is at a 1000 year high.
Natural and man-made variations have collectively caused increased melting of the Antarctica ice sheet.

It's not as significant an increase as you think.

It's important to remember what that "largest ice extent on record" means. That "on record" means in the satellite era. Data from before the satellite era (pre-1981) are rather spotty. Except they aren't.

There's a nice proxy for sea ice extent, at least during Antarctic summer, in the locations at which whalers made their catches and established their factory ships (Williams 1997). In the first half of the 20th century, whalers sought species that concentrated near the edge of the Antarctic sea ice. By the early 1930s whalers had developed a practice of anchoring factory ships within 20 km of the ice edge and followed the ice southward as summer progressed. This practice continued throughout the 1930s and resumed after WWII through to the mid 1950s. The practice was later restarted in the mid to late 1970s. Every whale caught by Norwegian whalers was tagged with date, latitude, and longitude. The practice of setting up shop near the ice edge gave Williams a nice way of estimating the pre-satellite era ice extent.

What Williams found was that summer Antarctic sea ice suffered a massive decline that continued throughout the 1950s and 1960s. The ice levels we are seeing now, at least during Antarctic summer, are on par with the levels seen eighty years ago.

The Interdecadal Pacific Oscillation is strongly in its negative phase.

The Interdecadal Pacific Oscillation (IPO) is highly correlated with a hiatus in perceived global warming and also with increased precipitation in the Antarctic (Meehl 2013). An increase in precipitation means that surface waters are less salty (increasing the freezing point) and cooler. The combination of reduced sea surface temperatures and reduced salinity makes for increased ice formation during the Antarctic winter during periods when the IPO is in its negative phase.

The Southern Annular Mode is at a 1000 year high.

It has long been suspect that stronger winds are one of the causes of the increase in the Antarctic sea ice levels (Zhang 2007, Zhang 2014). Winds help create polynyas, open areas of water surrounded by ice. That open water is subject to freezing during the Antarctic winter. Not only are the winds strong now, they are stronger than they have been for at least 1000 years (Abram 2014).

Natural and man-made variations have collectively caused increased melting of the Antarctica ice sheet.

Just as increased precipitation leads to increased ice formation, so does increased melting of the continental Antarctic ice sheet. And the ice sheet is melting (Shepherd 2012, Rignot 2013). Gravity measurements from the GRACE satellites, combined with ice height measurements from ICESat collectively show that Western Antarctica and the Antarctica Peninsula are decreasing in mass, and at a significantly greater rate than the slight increase in the mass of the Eastern Antarctica ice sheet. This influx of cold, fresh water during the Antarctic summer makes for increased sea ice production during the Antarctic winter.

References

Abram, N. et al., "Evolution of the Southern Annular Mode during the past millennium," Nature Clim. Change, (2014)

Meehl, G. et al., "Externally forced and internally generated decadal climate variability associated with the interdecadal pacific oscillation,"J. Climate 26 (2013), 7298–7310.

Shepherd, A. et al., "A Reconciled Estimate of Ice-Sheet Mass Balance," Science 338.6111 (2012): 1183-1189.

Rignot, E. et al., "Ice-Shelf Melting Around Antarctica," Science 341.6143 (2013): 266-270.

William, K. "Abrupt mid-twentieth-century decline in Antarctic sea-ice extent from whaling records," Nature 389.6646 (1997): 57-60.

Zhang, J., "Increasing Antarctic sea ice under warming atmospheric and oceanic conditions," J. Climate, 20 (2007), 2515-2529.

Zhang, J., "Modeling the Impact of Wind Intensification on Antarctic Sea Ice Volume," J. Climate, 27 (2014), 202–214.


What is the CO2 concentration by altitude and why? Here is a measurement of CO2 concentration by altitude measured by aircraft:(from Pulsed airborne lidar measurements of atmospheric CO2 column absorption)

Is this the usual vertical structure of CO2? Why is it at a higher concentration close to the surface and then uniform at a certain point?

The volume of carbon dioxide in the atmospheric column becomes uniform at altitude because the sources and sinks for CO2 are generally at ground level and, as it rises, CO2 becomes well-mixed into the atmosphere.

This is why, for example, David Keeling began the measurements for what would become known as the Keeling Curve at a station 3.3 kilometers above ground level at Mauna Loa.

At ground level, CO2 levels will be heavily influenced by local and seasonal sources such as forests, grasslands, and human activity. That is, if you have a city or industrial area, CO2 emissions will be high due to the burning of fossil fuels. In the case of nature, forests and grasslands will absorb CO2 during the local spring and summer when they grow and emit CO2 in fall and winter as they decompose. (Seen in the annual wiggles in the generally rising Keeling Curve.)

The specifics will vary by location. In the case of your graph, this late-fall test proofing lidar against balloon measurements over Oklahoma on Dec. 7, 2008 shows CO2 at about 395 ppm at about a half a kilometer, declining with altitude so that at about 3.3km, the measurement is around 385-386ppm.

At Mauna Loa, at 3.3km, the NOAA monthly CO2 data average for December 2008 was 385.56ppm.


WRF: EPSG code or spatial reference for Lambert conformal, Mercator and polar stereographic projections I'm building an R package (https://github.com/ibarraespinosa/wrftools) to read namelist.wps and return a dynamic map which you can make zoom. In my case, it would be very beneficial because writing a namelist.wps can be tricky. The problem is that I need to know the EPSG or spatial reference (http://spatialreference.org/) to transform the spatial data to WGS84.
Hence:
What are the EPSG code for:
Lambert conformal, Mercator and polar stereographic projections

Thanks

Edit 1: According to the WRF Manual , page 3-10: "As a general guideline,

the polar stereographic  projection is best suited for high-latitude WRF domains,
the Lambert conformal projection is well suited for mid-latitude domains, and
the Mercator projection is good for low-latitude domains or domains with predominantly west-east extent."

What I want to do is to tell R how to recognize these projections (spatial references), so that I can plot into the map.

Note: The example is from Brazil but the idea is that it can be used anywhere.

I would like to know:

If projection is lambert, the EPSG code is XX or the spatial reference is "+proj=lcc +lat_1=YY..."

Thanks

Spatial reference systems are coordinate systems that can be geographical coordinate systems defined on a model ellipsoid or projection coordinate systems.

A projection coordinate system is defined by four groups of parameters:

model ellipsoid,
projection type
projection parameters
measurement unit

EPSG codes refer to complete spatial reference systems or model ellipsoids.

You are saying that you want an EPSG code for projection coordinate systems that  use WGS84 as model ellipsoids and Mercator, Lambert conformal conical, and stereographic projections. These projections require additional parameters such as the central meridian and origin latitude. Choice of parameters depends on your region of interest.

You could start with EPSG:4326 which is a geographical coordinate system with degrees as units.

Next, since your region of interest seems to be in the south of Brazil, consider EPSG:32722 that stays for Universal Transverse Mercator zone 22S and uses the WGS84 ellipsoid.

For a Lambert Conformal Conic projection consider ESRI:102015 that stays for South America Lambert Conformal Conic. This spatial reference uses a model ellipsoid that is different from WGS84, so this might be a problem for you. The standard parallel numbers for this projection are 5S and 42S meaning that the distortion would be greater for regions that lie away from these latitude, i.e. the Northern hemisphere or the Antarctic regions.

Finally for a Stereographic Polar you might consider EPSG:3031. An Antarctic Polar Stereographic projection coordinate system that uses WGS84 as a model ellipsoid.


How many BTU per cubic meter does typical paper waste yield when burned in a modern domestic fireplace I am brewing on an idea where instead of cursing and throwing all our physical junk mail in the paper recycling bin, we process it into pellets to be burned in our fireplace as free fuel.

Before I start I would like to run the numbers but I am having a hard time finding the actual effect of burning said paper.

According to this page regular birch firewood will burn at 14 million BTU per cubic meter (20 per chord). What is the comparable amount for waste paper?

About 12 million BTU, or 3.5 MWh.

I searched for paper btu and got loads... of... hits.

Seems like 7000 BTU/lb is a decent starting point, or $1.6 \times 10^7\ \mathrm{J/kg}$. If we say a ream of letter-size paper weighs about 5 lb, then we can calculate that paper yields about $1.2 \times 10^{10}\ \mathrm{J/m^3}$ when burned — enough to heat the average US house for 15 weeks.


How to measure voltage differential across different altitudes Imagine two points, one directly above the other (
Point A - 10,000 feet (PA)
Point B - 20,000 feet (PB)
Imagine there's voltage potential between those two points
Q1: How could you measure the voltage between those to points?
Q2: What if the points were at the same altitude, but 10 miles away from each other. How could you measure the voltage potential? (i.e. PA is in Ohio at 10k feet and PB is in Indiana at 20k feet altitude - ground distance between the two points is 10 miles)
Q3: How could you determine if the potential was oscillating?

Q1: I imagine you could measure the potential difference using weather balloons. Send one balloon up to 10,000 ft (Balloon A) and one to 20,000 ft (Balloon B) with wires connecting them to a voltmeter. The challenge here is to account for the wire resistance, which, if the potential difference is low, will in all likelihood interfere with the measurement. If the difference is too low to be measured, you would have to amplify the voltage and then account for the amplification and wire resistance.
Q2: I would try using weather balloons again, but obviously Balloon A and Balloon B would be at the same altitude but 10 miles apart from each other.
Q3: Instead of a voltmeter measure with an oscilloscope. There's going to be noise no matter what; what oscillations are produced by noise and what is actual oscillations is a judgment call. I would say that truly oscillating potential difference is likely to be low frequency, so to filter out high frequency noise connect the circuit to a low-pass filter before processing with the oscilloscope.
Another way to determine oscillations is to measure the voltage with a data logger and post-process with computer software; any programming language that can easily manipulate large amounts of data would be sufficient, even excel would work. Plot the voltage vs time using a linear regression model to smooth the noise out. As an example, python's numpy has a regression function called polyfit. With a linear regression model and a moving window you will truncate the beginning and end of the dataset, but that shouldn't matter if you have a lot of data.


Are pumps used in geothermal systems? The water held underground in a geothermal system is under high temperature and pressure. Are pumps used to raise the very hot underground water to the surface or does the water rise under its own pressure? One source says that the water is pumped up[1] while another says that it rises on its own[2]. I am not sure if I just misunderstand the wording. Does anyone know which is correct?

[1]: energy.gov/eere/geothermal/electricity-generation

[2]: www.youtube.com/watch?v=kjpp2MQffnw

Pumped systems are much more common. However, there are some artesian type hot springs where the water flows spontaneously and is not replenished in the immediate area.


Is silicon dioxide (silica) found in all types of soil on the planet? Known that it is found in sand, silt and clay but is it found in all soils?

tl;dr

Silica is everywhere, in everything. The amounts can be close to 100% in quartz sand, or less than 1% in things like peat or limestones (and derived soils). Finding completely pure soils (let's say less than 0.1%) is wishful thinking.

Silicon dioxide (or silica, or silicon oxide, it's all the same thing) can exist in two "forms":

As the compound, most commonly known as quartz, but also all kinds of other materials such as chert, agate, jasper, opal, etc.
As the chemical component in other materials (think oxygen in water). Most of the hard and brittle solid materials you know have silica as a chemical component in them. This includes most rocks, clay minerals, concrete, bricks, ceramics, etc.

Silica the compound (as quartz and others) is one of the most abundant materials on the surface. Sand (the white-yellow stuff) is commonly 99% quartz. Silt and clay are actually definitions of grain size, not chemical composition. Most soils that are silt or clay size also have abundant quartz in it. Quartz is a component of dust. This stuff gets everywhere.

For soils that don't have quartz proper in them, most will have silica as a chemical component. Clay minerals, pyroxenes, amphiboles, micas, feldspars, and all silicate minerals (which are the most common rock forming minerals on Earth).

It is easier to talk about the rocks and soils that don't have any silica in them.

Peat and other organic soils (coal?). These form by decay of plant material, and should not have any silica in them. However, since silica is a component of dust, and dust accumulates when these soils form, there will be some amount of silica. The amount can vary from a few percent to as little as a tenth of a percent, but it will be there.
Evaporites. Things like salt, gypsum, etc. These are chemically precipitated rocks which should not have silica. Then again, dust. There will be some amount.
Carbonates. Limestone is calcium carbonate. Limestones are rarely pure though, and the most common contaminant is - you guessed it - silica. Because of dust. Or just silicate sediments floating in the sea when the limestones form.


What is the geologic origin of Cryolite, and could there be more? Cryolite is a mineral of aluminum (Na$_3$AlF$_6$). The only known natural deposit was found in Ivittuut, Greenland. It was mined from 1854 to 1987 and yielded 3.7 Mt of Cryolite ore.

Basically my question is, why is this the only cryolite deposit known? What is the origin of it and why didn't any more form?

There are a lot of similar islands in the arctic: Canadian islands, Russian islands, Scandinavia and Svalbard, etc. Do geologists believe other Cryolite deposits are out there, just not discovered yet?

Ivigtut Cryolite deposit, Ivittuut (Ivigtut), Arsuk Fjord, Sermersooq, Greenland deposit  is the first and largest occurrence of Cryolite but it is not the only location to report Cryolite.

Some of these other locations listed below have produced collectible specimens but cryolite does not occur in large enough quantities to be mined.

Other important locations are: Reference
(I have seen specimens from these locations)

ST PETERS DOME PEGMATITE PROSPECT, Pikes Peak Colorado
Francon Quarry Mt St Hilaire, QUEBEC

(other listed locations, Reference)

MONZONITE GROUP, Gunnison County Colorado
FANNY GOUGE MINE, Yancey Co. North Carolina
BARINGER HILL MINE, Llano, Texas
MC GUIRE PIT Marathon Wisconsin.
Also reported from near Miass, Russia.

I also suspect there are other Canadian locations but Canada publishes less mineral data than the United States does.

Cryolite occurs in syenite vein deposits (igneous rock which is quartz deficient) which had abundant amounts of fluorine.

There are 13 other known mineral specimens that contain primarily: Na, Al, F.
Cryolite is the most common mineral, due entirely to the Ivigtut deposit.
The geologic conditions at the Ivigtut deposit led to deposition of cryolite instead of an other mineral phase containing  Na, Al, and F.

I believe additional deposits with cryolite may be found in the future but the Greenland deposit is likely to remain the first and most important deposit.
There are a handful of completely unique ore deposits on earth, Ivigtut Cryolite deposit is one of them.

See zincite from Franklin New Jersey as another example where a specific mineral was only ever commerically mined from a singular location.


Does the relative abundance of radioactive isotopes reflect their half-lives? In Radiometric Dating: A Christian Perspective, the author argues (persuasively, I think) in favor of the mainstream interpretation of radiometric dating (as opposed to the claims of young earth creationists). He says the fact that short-lives isotopes are generally not found on Earth is evidence showing that the Earth is billions of years old.

  Just about the only radioisotopes found naturally are those with very long half-lives of close to a billion years or longer.... The only isotopes present with shorter half-lives are those that have a source constantly replenishing them...

  The Earth is old enough that radioactive isotopes with half-lives less than half a billion years decayed away, but not so old that radioactive isotopes with longer half-lives are gone.

I would guess that some of these shorter-lived elements still exist in minute amounts because a decay curve has a long tail, but is the basic statement correct - that shorter-lived, non-replenished radioactive isotopes are absent (or nearly so) from Earth?

Where can I read more about this?

Clarification: I didn't make it clear enough, but I'm specifically asking about the relative abundance of non-replenished radioisotopes - those that are not produced on Earth by natural processes. Eg, excluding carbon-14 (produced in the atmosphere by cosmic rays), excluding thorium-230 (produced by the decay of uranium-234), etc.

Yes, the general idea you have is correct: isotopes with relatively short half-lives are found in quantities so minute as to be marginally detectable, and then only if they are being produced by something else: either as decay products of some long-lived isotope, or by cosmic-ray bombardment.
An example is gadolinium-150. This has a half-life of about 1.8 million years, and I believe simply does not occur naturally at all.  Gadolinium-152, with a half-life of about $10^{14}$ years, does occur naturally.
So whatever primordial gadolinium-150 there was has gone (in 4 billion years, you get a decrease of a factor of about $10^{669}$: the Earth contains around $10^{50}$ atoms, so there is a chance of $1/10^{619}$ of finding an atom of it on Earth).  Unfortunately in order to know how much there was you would need to understand nucleosynthesis in supernovae in considerable detail (gadolinium is heavier than iron and so originated mostly or entirely in supernovae), and I don't.  But I think it's safe to say that they probably made at least some, on the grounds that anything we do in the way of crashing particles into things to make isotopes (which we have done to make $^{150}\mathrm{Gd}$) supernovae also do, except much, much more.  If we assume the Earth was only a million years old, then about $68\%$ of the primordial $^{150}\mathrm{Gd}$ would still be here: we'd find it.
Now of course, there are two catches here:

perhaps the $^{150}\mathrm{Gd}$ has all gone somewhere secret where we can't find it;
this all rests on the idea of supernova nucleosynthesis.

So to answer the first: if this was true it would be utterly extraordinary.  In particular we spend a lot of time (really a lot of time) trying to isolate different isotopes of elements: people go to really enormous efforts to distinguish between different isotopes of uranium for instance.  This is something you can't do chemically, because the different isotopes have the same chemical properties.  Instead you have to do things like spin them in very high-speed centrifuges, or use mass spectrometers.  These things just don't exist naturally on Earth, so, since we do find other isotopes of gadolinium (including ${}{150}\mathrm{Gd}$, which is not stable), how come we don't find this one?  Well, we don't find it because it's not there, of course.
The second problem is perhaps more severe: people who believe the Earth is a million years old probably have no truck with supernovae at all, or are happy to just argue that, well, supernovae don't produce some isotopes because they just don't.  I don't think there's a useful argument against that.


Why are there more intense earthquakes in Iran than in Iraq? Why are there more intense earthquakes in Iran than in Iraq, if they are so close together?

I often hear news items of earthquakes in Iran that are higher on the Richter Scale than those that happen in Iraq.

Are there maybe more earthquakes in Iraq with lower magnitudes, while less earthquakes in Iran with higher magnitudes?

These two images probably explain it best:

This is a map from the US Geological Survey Earthquake Hazards Program, which shows all recorded large earthquakes in the region from 1900 to March 2012.

The black lines are tectonic plate boundaries. The plate in the middle is the Arabian Plate. The current movement of that plate is show in this image from mediawiki:

So the Arabian plate is currently pushing north against the Eurasian plate, and sliding under it, causing uplift in Iran, and probably causing various slip and thrust fault lines. The pressure on those fault lines is released as earthquakes.

Iraq is not so affected, because it is on the plate. Maybe it will be in a few hundred thousand years :)