How we can find hot spring genesis time? Is there any way we can calculate the time when a particular hot spring come into existence? Also I wanted to know what is average time period for a active hot spring in general, whether it can flow for geological time scale or can be only in 100s of years?

The answer to the first question is a maybe, hot-springs often have mineral saturated water that can create layered deposits which may be datable, much like tree rings. If reasonably uniform flow and mineralisation rates can be demonstrated over time then reasonably accurate dating may be possible.

As to the second question, we have a saying "how long is a piece of string?" meaning there is no universal answer, some springs may be seasonal, only flowing for a few months at any given time, while others may flow continuously for hundreds of years then stop abruptly for no apparent reason. There are no "in general" each and every set of geothermal plumbing is unique.


Thermohaline Circulation in the Oceans I'm slightly confused by how thermohaline circulation works in the Earth's oceans. Is it different  for surface water as opposed to deep water? I thought that warm water from the equator is transported to the poles, cools down, and then returns to lower latitudes. Is my thinking incorrect? Isn't water denser near the equator because of higher salinity? How does this impact the ocean circulation?

Thanks!

Salinity and temperature both affects the density of sea water. When water with a fixed salinity cools down, it becomes heavier and sinks. In the same way, when vapor or ice removes water from sea water, the remains is more saline and heavier.
Thermohaline circulation can work as you describe. Surface water in the tropics is saline, due to evaporation, but warm due to high temperature in the atmosphere and therefor low density. As it reach colder climate (less solar energy per area), it cools down and the high salinity makes it sink. Surface water in polar regions also get heavier as ice is formed of water and leave the salt behind in the sea.

This is very simplified model, you can read more on the topic here and here.


How is surface pressure generally measured, and at what actual height? In various atmospheric equations, surface pressure is one of the variables used. For example, in calculating the density of air or pressure-corrected relative optical air mass. How is surface pressure measured?

I imagine it's the pressure at the height of a sensor on a weather station. Is that considered effectively pressure at Earth's surface / a good-enough approximation, or do scientists generally adjust measurements from weather stations to be corrected for the height difference between the sensor and Earth's surface? Or is surface pressure measured by a sensor actually at Earth's surface?

When you look on meteorological maps the "surface pressure" is actually the reduced MSLP (mean sea-level pressure) value.  See this NWS page for more info.  So whatever height the sensor is at above the ground, they regardless compare that height back versus the sea-level to report the pressure.

I always figured barometers were sited along with the main instrument set.  Those indeed will all generally be raised up off the ground certain heights (aside from any soil temperature thermometers) to prevent issues with any standing water or snow cover.  See for example the instrument list and extensive pictures for Oklahoma Mesonet site locations (slightly different setup, but the 2 meter temperature and 10 meter wind are widespread standards).

But I was surprised to read in the ASOS User's Guide that:

  At virtually all locations, the pressure sensors are located indoors
  within the ACU.

And:

  The ACU, which is the central processing unit for the ASOS, is usually
  located inside a climate controlled structure, such as an observing
  office or control tower building. It ingests data from the DCP(s) and
  pressure sensors, and is capable of accepting information from the FAA
  New Generation Runway Visual Range (NGRVR) system.

So it sounds like the barometer is often not on site, and there are indeed no specifications for height.  But since it's reduced to sea level regardless, the elevation is all that really matters to reduce it to MSLP, and so some variation in height of the sensor shouldn't matter.


How Warm Was the Paleocene? It's been said that 55 million years ago, a massive carbon surge raised global temperatures by five to eight degrees (or, in a more preferable translation, nine to 14.4 degrees Fahrenheit).  This catastrophe was known by scientists as "The Paleocene-Eocene Thermal Maximum", or PETM.  It showed how warm the Eocene was before the opening of the Drake Passage which left Antarctica to be iced, yet it never mentioned what the weather or climate was like BEFORE the PETM.

So the simple question is:  How warm was the Paleocene epoch?

Redrawn after Zachos et al. 2001.

This is a plot of the Cenozoic variations of $\delta\ce{^{18}O}_{Cibicidoides}$ according to Zachos et al. 2001 (this is a bit outdated now but the Paleocene is roughly the same in more modern curves such as Zachos et al. 2008 or Cramer et al. 2011). It is supposed to follow variations in deep ocean temperatures and thus reflect the climate state at a given time. The Paleocene is the timeframe delimited by the two vertical bars (you can see the PETM quite clearly on one of the two bars).
From that plot it seems the Paleocene deep-sea temperature prior to the PETM is roughly at the same level at it is during the Middle Eocene (ca. 45 Ma), i. e. warmer than most of the Cenozoic but colder than the Early Eocene or most of the Cretaceous.
There isn't actually that many studies focussing on the Paleocene itself, this is clearly a time interval that is studied so far mostly because of the K/T boundary or the PETM, i. e either because of its start or its end.


Estimated volume, daily or annually, of sea level rise due to melting ice? Its a big number, difficult to estimate I assume. But is there a peer reviewed estimation (at current conditions) of the volume of daily or annual increase of water?

I don't know if this helps, but since you have no response yet perhaps I can offer some thoughts.Your question is problematic due to the fact that volume itself is variable according to the temperature of the water. If you look at the Nasa site concerning sea level change:

  Sea level rise is caused primarily by two factors related to global
  warming: the added water from melting ice sheets and glaciers and the
  expansion of sea water as it warms.

(some nice graphics here showing change amounts)

This expansion due to warming literally changes the volume of the water, adding to the sea level rise. So glacial melt may be measured or estimated, but the change in sea level caused by this volume of water is variable; over time it will change temperature and expand. But this isn't straightforward either. Nasa again:

  Thermal expansion of seawater can be the product of regional
  phenomena, such as El Niño, the periodic warming of the eastern
  tropical Pacific. But some of these regional cycles so far show no
  direct link to long-term global climate change—despite, at times,
  independently exerting a powerful short-term influence on global
  climate.

So bottom line is that it is easier to measure the amount of change, then to calculate direct figures concerning how much actual water was involved in causing that change. Hope this helped.

Update: There is some specific data on another page of the Nasa site concerning the volume of water being generated by the melt of the Greenland Ice Sheet:

  The estimated total loss is in the range of more than 200 to more than
  300 gigatons per year (1 gigaton is approximately 264 billion gallons
  of water. Melting 365 gigatons of ice would add 1 millimeter to global
  sea level; there are 25.4 millimeters in an inch).

This does give you some approximations in gallons per year of one of the main contributors to the sea level rise.


Is the Great Artesian Basin a closed basin? Areas where topography prevents the outﬂow of water are called closed basins. Is the GAB a closed basin? What if external bodies of water flowed in? Is that still "closed"?

In the far north of the Great Artesian Basin, there is groundwater outflow to the Gulf of Carpentaria. Everywhere else the aquifer behaves as a closed basin with outflow in the form of vertical seepage (e.g. to the Mound Springs of South Australia), artesian overflowing boreholes, and pumped boreholes. There may once have been hydraulic connection to the Southern Ocean, but that ceased several millions of years ago - not such a long time when one considers that the longest through-flow time of groundwater, from east to west, is about two million years.


When will glaciation resume? Has global warming delayed return to global cooling? As far as I understand, we are currently living in the Holocene, an interglacial period of the Quaternary glaciation, i.e. the current ice age that has so far lasted 2.6 million years. The Holocene began about 12,000 years ago. While humans emerged about 200,000 years ago, human civilization is almost entirely coterminous with the Holocene.

Questions:

(A) Are there any generally accepted estimates for how long the Holocene will last?

(B) Is anthropogenic global warming delaying the return to glaciation?

First, great question, though answers are likely to be non specific and speculative.

  As far as I understand, we are currently living in the Holocene, an
  interglacial period of the Quaternary glaciation, i.e. the current ice
  age that has so far lasted 2.6 million years. The Holocene began about
  12,000 years ago. While humans emerged about 200,000 years ago, human
  civilization is almost entirely coterminous with the Holocene.

As others have said, defining our current period as the Holocene is iffy.   Human influence is pretty huge, and perhaps, even as many as 6,000-7,000 years ago the growth of the agricultural revolution, some farm animal domestication and early, though much smaller, deforestation may have played a role in climate, at least, I remember reading that, though a quick google didn't provide a good source, but I've read that.   It's probably not consensus though, just some people's opinion.

  (A) Are there any generally accepted estimates for how long the
  Holocene will last?

So, how long?   There's 2 very different answers to this.

First one, if we take out the human effect, or, lets say, in the relatively near future we "fix" our CO2 and other human effects on the planet and return the Earth mostly to how it was.   Then the answer is kind of simple, we just Look at past warm periods and make an estimate from those.

Without human activity the Holocene would very likely be just another inter-glacial warm period between ice ages in the continuation of the Quaternary with a similar length of time.  See chart:, If the average length of inter-glacial warm period is about about 20,000 to 40,000 years we can just subtract 11,000 from that and reach a rough estimate.

Or, if you want more accuracy, you can look closely at the 3 orbital cycles and calculate based on that - but I'm not going to do that as it would get more complicated.  More on that here.

It's also likely that there would be a cooling period within that time-frame.  We can see cooling, like the little ice age, without it being an actual ice age.

  When will glaciation resume? Has global warming delayed return to
  global cooling?

  (B) Is anthropogenic global warming delaying the return to glaciation?

First, it's worth pointing out that returning to global cooling and a return to glaciation aren't entirely the same thing.   If, lets say, we continue our CO2 footprint/production and reach 450 PPM before we cut back enough to level off for a few decades, then, cut back enough to see the oceans gradually take in CO2 and reduce the levels in the air, we could see a gradual global cooling within 100 years or so - maybe, provided the higher ocean temperatures and Albedo drop due to loss of ice cover didn't created a new equilibrium.   But in general, the earth can go through cooling periods without glaciation, so those 2 questions are similar but not entirely the same.

But in general, calculating glaciation with the human factor, it's a much harder question, especially since we can't see the future and how high CO2 levels will get.

Modern ice ages are defined as an advancing glaciation across a significant range of the Northern land, which, as pointed out above, coincides well with Milankovich cycles, but to actually have that happen, you need a few things in place.   Milankovich cycles don't cause ice ages all by themselves, cause they were there during non ice ages too.

The modern ice age cycle only started about 2.6 million years ago and it is thought to have been brought about by the formation of Isthmus of Panama about 5 million years ago, which separated a current between the Atlantic and Pacific Oceans which helped the arctic ocean cool and freeze over.  Shortly after that Isthmus formed, the Earth began to cool.   See here (chart from Milankovich link above).

Modern ice ages also coincide with falling CO2 levels, and while the CO2 drop follows the temperature drop, there's a reason for that.  Colder oceans hold more CO2, so the Atmospheric CO2 drops when temperature drops.  This serves as a feedback loop where cooling leads to more cooling and that's part of why ice ages are as big as they are.   Albedo is another feedback loop, so the trigger to get an ice age started is actually pretty small.   The Orbital cycles of the Earth are thought to only contribute about 1 degree of cooling in and of themselves and the other 9 or so degrees of global cooling between peak ice age and average Holocene is thought to be caused by these feedback mechanisms, primarily albedo and drops in atmospheric CO2.

So, there's 2 questions to ask as to whether man made global warming will prevent the next ice age and perhaps future ice ages.   We know that the Milankovich cycles will continue, but will CO2 be low enough for the cycle to lead to glaciation, and, how fast will CO2 levels drop, so, over the next 10,000 - 30,000 years.    Nobody knows the answer to those questions.

Looking at the last 800,000 years or so, based on ice-core samples, warm periods between ice ages you usually have about 260-280 PPM and peak ice age periods, about 180-200 PPM CO2 with the ranges in between, mostly during transitional periods.  When these changes occur, most of the CO2 is believed to be absorbed into or released from the oceans, though I see no reason why a smaller portion of the change couldn't be driven by changes in living bio-mass corresponding to the changes in temperature, ocean size and grow-able land area.

By burning fossil fuels, we've added carbon that was effectively removed from the Carbon cycle. For a rough calculation for how much, every year we add a bit over 30 billion tons of CO2 by burning fossil fuels every year.

The Atmosphere, at 270 PPM with a mass of the Atmosphere, about 5.148 x 1018 KG is about 2,320 billion tons.   Since the industrial revolution, CO2 PPM has increased to about 400 PPM, which is an increase of about 1,030 billion tons (atmosphere only) with roughly about 400 billion tons (rough estimate), having been absorbed into the oceans.

Oceans are estimated to store about 50 times the CO2 than the Atmosphere, Source, so assuming that's accurate, Oceans currently store over 110,000 billion tons of CO2 and since the industrial revolution, we've added (ballpark) 1,400 billion tons from burning fossil fuels - about a 1.2 - 1.3% increase to the total CO2 in the Oceans, Air and Land-biosphere.   That's the crux of the question, what effect will that have.

Over enough time, like, 10,000-30,000 years when the next ice age might be due, the oceans could absorb most of the atmospheric CO2 and the effects could be fairly small.   But as the Earth warms and Oceans warm and warming oceans increases the Atmospheric CO2 cause oceanic absorption drops.  With warmer oceans there will be a new equilibrium and with that in mind, it's entirely possible that the new atmospheric CO2 equilibrium, if left to it's own devices, might already be sufficient to prevent ice ages for a long time, perhaps a few hundred thousand years.

Predicting atmospheric CO2 levels 10,000 to 30,000 years from now, for all practical purposes, impossible, and that's what we'd need to know to estimate if we've stopped the next ice age or not.   What we have done is increased the amount of CO2 in the biosphere of earth by about 1.2–1.3% and since we continue to burn fossil fuels, we're likely to have created an increase of 2% before alternatives are in place, perhaps a bit more than that.

All of this, however, is probably irrelevant, cause we have some ability to trap CO2.   It's not easy, but we can do it and if, as our technology improves and we begin a gradual CO2 trapping program, we could re-start the next ice age in 10,000 years or so, assuming that's what we want to do.   Now, I don't mean to make light of the CO2 problem cause we appear to be facing very big and real issues over the next 20-50-100 years and that's much harder to avoid at this point, but over 10,000 years, we could probably fix our CO2 situation and bring the Earth back into the ice age cycle, or, we could use CO2 to avoid future ice ages if that's preferred.  Collecting and trapping 1–2 trillion tons of fossil fuel generated CO2 isn't easy and we don't have nearly the technology to do that today, but over 10,000 years I feel pretty confident that we could be able to do it, provided we keep progressing technologically.


Is it true that earthquakes are not felt in a cave? I took a tour of a cave in northern California last weekend. The tour guide asked us, "If an earthquake occurred, what would we feel in here?"

My answer was, "fear," but she said we would feel nothing - that earthquakes are not felt underground.

Although I did not contest her assertion, I have my doubts about it - after all, don't earthquakes normally have their epicenter underground (well, all the time, I reckon, as they can't emanate from the air)? And if an earthquake happened to erupt from within a cave[rn], wouldn't it most definitely be felt there?

I would think one might even end up with a stalagtite stuck in his noggin.

UPDATE

And, if I'm right (that there could be a whole lotta shakin' goin' on while on a journey to the centre of the earth), has anybody lived to tell the tale and really done it (told the tale)? A first-hand account could be riveting.

Ground motion results due to passage of elastic waves. Now there are different kinds of waves, e.g., P waves, S waves, surface waves, etc. Most of the shaking (and therefore damage) is caused by surface waves. So if you are in a deep cave or mine then the amount of shaking you might experience can be much lower than on the surface. This of course assumes that the mine or cave is not right on the fault, but some distance (10s of km) away.

Having said that, there are some situations (based on the type of earthquake and local geology) in which waves can interfere constructively to cause significant shaking even at large depths, but this only happens in certain areas and not everywhere.

In many ways elastic wave propagation is similar to acoustic or water waves. Imagine a small explosive source in a lake/pond, let's say 50 m underwater. After the explosion there will be more 'shaking' on the surface, but not much underwater unless you're extremely close to the explosive source.


What methods exist for remote profiling of oceanic columns? Remote sounding of the atmosphere is a well-established method used extensively used extensively for operational weather forecasting and scientific research.  Active or passive instruments carried on satellites (or aircraft) can measure profiles of temperature, pressure, trace gases, and particulate matter.

Is anything similar possible for a ship sailing on the ocean?  What methods exist, in theory and in practice, to remotely sense a profile of temperature, density, salinity, etc., from the ocean floor to the ship?  Or can such profiles only be obtained in-situ?

There are a number of programs and instruments that sample the ocean autonomously. Examples of such programs are:

The ARGO program (http://www.argo.net/): Currently around 3000 floats are freely drifting in the ocean measuring temperature, salinity and in some cases velocity of the upper 1000-2000 meters of the ocean. The floats drift for around 10 days most commonly at 1000 or 2000 meters and then conduct a vertical profile to the surface where they transfer the data to a satellite.
RAFOS floats (http://www.whoi.edu/instruments/viewInstrument.do?id=1061): They map the ocean currents using the SOFAR channel (a horizontal layer in the ocean where sound speed is minimum).
Gliders (http://www.ioos.noaa.gov/glider/): A type of autonomous underwater vehicle (AUV) that uses buoyancy to control its vertical position in the ocean. They sample along predetermined routes and can be equipped with instruments to measure temperature, salinity, turbidity, velocity...
Other AUVs: Most other AUVs use propellers powered by rechargeable batteries and are able to carry a lot more instruments, but are limited to shorter missions.

Measuring oceanographic interior conditions remotely is much more challenging. While satellites provide data for sea surface (or near-surface) parameters, such as temperature (e.g., MODIS), salinity (SMOS & Aquarius), height (e.g., Jason 2) and color (SeaWiFS, MODIS), remote interior data are more challenging to acquire.

Seismic oceanography is a recently developed technique that uses multichannel seismic reflection to characterize the ocean interior. It provides continuous mapping of the finer structure associated with the thermohaline (temperature and salinity) structure of the ocean. One of the best examples is Holbrook et al., 2003 Science paper (sciencemag.org/content/301/5634/821.full). You can find more information in: steveholbrook.com/research/seismic_oceanography and www.utm.csic.es/so


Who would know how to manage rainwater erosion on a sloped property? I'm a meteorologist with little experience in hydrology. I'm studying my land with the rainwater flow patterns during heavy rain events and looking to manage the erosion, flash flooding, and ponding on my property. Thankfully it backs up to natural wetlands. The main issue is that the ditch in front of our house overflows faster than it removes water downstream. Our neighbors frequently have to place sandbags at the front of their driveway to keep their garage from flooding.

I'm not sure where to go next. Any thoughts on where to look for more information?

Erosion:

Establishing a deep rooted vegetation may help.  What would work best
is dependent on where you live.  Your local conservation office would
be able to help with what would work best in your area.  This
site has some good information for choosing plants on slopes.
Rip-rap (rock) is also commonly used to help slow erosion.  The size
you would need would depend on the slope and flow of a the drainage,
if it would be within a drainage area.

Source: http://www.erosioncontrolnetwork.com/rip-rap/rip-rap.aspx
Another option would be gabion baskets, however they would be one of
the most expensive options.  Gabion baskets often look like chain
link fencing wrapped around rock.  In this way the rocks stay in
place and the can be placed in a more vertical position.

Source: http://www.svca.on.ca/page.php?page=erosionandfloodcontrol

Flash Flooding:

The first thing I would do is establish who is responsible for maintenance of the ditch.  The capacity may need to be re-established or increased if run-off from additional developments have been added to it.  If increasing the capacity of the ditch is not an option, I would see if I could construct either berms (a slight rise in topography) or swales (a minor trough in topography) to direct the water away from any structures on my property.  However, you would need to make sure that you are not increasing flow onto any other neighboring properties or impeding flow from any other properties.

Ponding:

Dry wells are often used to address ponding in yards.  They are
basically an underground chamber that water is directly to through
pipes.  Holes in the container let water slowly soak back into the
surrounding soils.  These need to be sized properly to accommodate
the volume of water one is trying to remove from the surface of their
yard.  Also, these may not work well in clay soils that the water
would percolate slowly into.  More information can be found at the
source link below.

Source: http://www.svca.on.ca/page.php?page=erosionandfloodcontrol
Rain gardens are a more decorative option that includes water storage
in a depression, water infiltration,and native vegetation. The basic
idea of a rain garden is captured in the image below.  Additional
helpful information can be found here.  Some municipalities may
also have funds available for installing rain gardens on private
property.

Source:
http://vienna-wv.com/portal/2013/07/18/what-is-a-a-rain-garden/

Again, I would definitely contact the local jurisdictional authority before I do anything.  There are many government agencies that have codes that need to be met.  Additionally, they would know what works best in your area and may have subsidies that would help defray costs.


How are stratigraphic limits defined before the Phanerozoic? International Commission on Stratigraphy defines the limits of geological ages and they create this chart:

Click on image for full view.
Acording to Wikipedia:

The standard stratigraphic nomenclature is a chronostratigraphic
system based on palaeontological intervals of time defined by
recognised fossil assemblages.
Source: chronostratigraphy, Wikipedia.

However, until Cambrian, there are not fossils (except chemical traces of unicells).
How are the limits between units defined at Precambrian?

The standard stratigraphic nomenclature is a chronostratigraphic system based on palaeontological intervals of time defined by recognised fossil assemblages.

That's wikipedia for you. This is incorrect. The point of a Global Boundary Stratotype Section and Point (GSSP) is to identify a global boundary with a very specific archetypical example. While a recognizable and global fossil assemblage is preferred, sometimes there are better choices and sometimes such assemblages don't exist.

For example, the stratigraphic boundary that marks the start of the Cenozoic Era, (and the Paleogene System, Paleocene Series and Danian Stage) is a millimeter thick layer of fossil-free clay near El Kef, Tunisia. This clay layer was laid down about 66 million years ago and can be found in many places around the world. This layer is distinct, unique, and occurs worldwide. That clay layer contains the remnants of the dinosaur killer asteroid.

  How are stratigraphic limits defined before the Phanerozoic?

Getting to point of the question, the base of the Ediacaran "is defined as the base of the Marinoan cap carbonate (Nuccaleena Formation) in the Enorama Creek Section of the central Flinders Ranges, Adelaide Rift Complex, South Australia." The GSSP is the archetype, but as with that thin layer of red clay, this layer of cap carbonate can be found in many places around the world. That layer of cap carbonate represents when a worldwide glaciation event ended.

All of the International Commission on Stratigraphy boundaries that predate the base of the Ediacaran are currently defined in terms of time called Global Standard Stratigraphic Ages (GSSAs). That's a fancy name for a rather arbitrary point in time.


Discrete distribution of daily rainfall How can I estimate the rainfall rate every ten minutes during a day having the total amount of rainfall during that day ?

Put a cylindrical beaker out in the open at mid day. Remove it at mid day on the following day. Measure the depth of the accumulated rainfall and divide by 24 to give the average rainfall per hour, and divide that by 6 to give the average per 10 mins. In the summer, some of your collected rainwater will be lost through evaporation, so to find that, put your beaker of water outside, but under some sort of roof. Measure the depth when you put it out, and measure it next day when you take it in. That will give an idea of losses due to evaporation, which reckoned in losses every ten minutes would by tiny. If there is not much rain but plenty of hot sunlight, things become tricky, because you will be measuring very tiny quantities. Other than that, you could camp outside and weigh your beaker every 10 minutes, but that's not something I would do myself. The roof I mentioned is only necessary if it is raining, because rain would destroy your figures for evaporation.


How did New Zealand's continental crust get split between two plates? In New Zealand today, the Alpine fault features two pieces of continental crust sliding past each other, with the whole Eastern side of the South Island falling on the Pacific plate.

But when New Zealand separated from Gondwanaland, it was entirely on it's own plate with the Pacific plate subducting beneath it.

How did most of the south island end up colliding with the very plate it used to be travelling with?

The continental crust and shelf of new zealand is one peice that has a fault running through it due to it running over a boundary between two oceanic plates. Continental crust cannot really* subduct due to its lower density so if forced onto a subduction zone they will actually slide over it onto the other plate. It helps of you remember oceanic crust and continental crust can exist on the same plate but have different properties.

Something similar has/is happening in North America the san andreas fault is caused by part of the north american continent running over the old east pacific (farallon) plate and spreading center, so now the portion attached to the north american plate is being dragged in one direction and peice sitting on/in the (west) pacific plate is moving in a different one. it is slowly pulling the continent apart and eventually may create an island like new zealand.

Here is more in depth discussion of strike-slip/transcurrent plate boundaries.

*small pieces can get dragged down but not much.


Sediment layer chronology In the new Cosmos series, Neil DeGrass Tyson in explaining different ways the age of the world has been determined, shows how sedimentary layers at the Grand Canyon are a fossil record of a lot of the Earth's history. He points out how each layer is (obviously) laid on top of the last, showing the chronology of various stages in the biosphere.

I remember learning how the Colorado river "carved" the canyons, on a trip there as a kid. You can visualize this -- the huge open canyons being eroded over millions of years, the riverbed turning grooves into valleys until enormous mesas are separated by the river. But, if the river "carved" the canyons, doesn't that imply the sediment layers were exposed from the top layers down, chronologically? How was all this fossilized life embedded in rock that at one point was a mile under the surface, that was later exposed by the river's erosion?

I'm not doubting the science at all, just trying to understand how the canyons formed.

In simple big picture terms, Sediments were deposited first from the bottom upwards (as you understand). Then the area was uplifted and the river eroded from the top down.

Most erosion is from the top down (there are scenarios such as dissolution and caves which are relatively rare exceptions). So here in Texas we find a large amount of the center of the state was covered with Cretaceous sediments which have since eroded away. We see signs of this from "outliers" - basically remnant caps of Cretaceous on the tops of hills.

As I say this is big picture viewpoint. The very bottom of the Grand Canyon has metamorphic rocks. And sedimentation will not have been continuous. There are gaps from erosion, uplift, etc. But yes the bottom is about 2 billion years old, and erosion of the canyon itself is "relatively" recent.


How large can local surface CO2 concentration vary due to natural processes? I'd like to have a rough idea of how large local surface CO2 concentration vary due to natural processes.

For example, a purely hypothetical experiment:

If I set up some CO2 monitors in a wide variety of locations around the globe (e.g. mid-ocean, jungle, desert, plains, tundra, mountaintop, beach...), say at 2 meters off the ground, and took some measures to avoid close proximity to substantial anthropogenic CO2 sources (industrial, transportation, population, farms) and fires or episodic geological sources (e.g. volcanos or magma pockets under lakes per @jamesqf), roughly speaking what might the variation look like?

A starting guess might be that they'd all be nearly featureless, around 400ppm, with only say +/- 10 or 20 ppm daily and yearly oscillations. Of course there is a whole lot of important science within those variations, but for the purposes of this question, I'd call those variations small.

Would my detector in a forest or jungle see higher peaks, or deeper troughs than one in a desert, or mid-ocean? What might the biggest excursions be? Might it ever reach down to 300 or up to 500 ppm due to natural processes?

The reason I'm asking is that while I tried to so some searches, it is very popular to show data from urban and suburban locations, where peaks of 500 or 600 ppm or even higher are seen that are attributed to wind direction and concentrated man-made sources, and that variation is not what I'm after. Here is just one example (48 hours and yearly) but there are many much larger studies published with sensors in urban areas.

There are many studies quantifying temporal CO2 variability for a static location. Conducting such studies isn't particularly difficult, the cost of equipment is low, and it's an easy way to publish meaningful results. You may have a hard time wading through all of the publications to select the few that mean anything to you, specifically.

A quick 2 minute search found this paper (among a slew of others), entitled, Diurnal and Seasonal Variation of CO2 levels of surface air in Garwhal Himalaya
in which this graph highlights daily CO2 variations over the course of a year, in mmol/mol. You'll have to look up the conversion to ppm CO2:

You may to search using these key words: CO2 variability, diurnal, yearly
Seasonal and diurnal variations in moisture, heat and CO2 fluxes over a typical steppe prairie in Inner Mongolia, China

Temporal variations of atmospheric CO2 concentration in a temperate deciduous forest in central Japan

Seasonal and Diurnal CO2 Patterns at Diekirch, LU

Interannual variability in the atmospheric CO2 rectification over aboreal forest region


Measuring Transect Length on Sea Floor I was wondering if anybody had any insight or thoughts on a technological bottleneck we are facing in data collection.

Basically, we have vessels (single operator) dig the substrate for collection purposes in water depths generally shallower then 35' (maximum of 35' but average about 15') via bullrake (large clam rake with a telescopic handle). The digger stands aboard a vessel with the rake and is drifting along by current/wind, thus completing a "transect" after a period of time based on how quickly the vessel is drifting. Transects typically range from 5-50m in length. Currently we are measuring the length of the transect (which is define as the point at which the rake first begins digging along the bottom until the point digging ceases on the bottom) via GPS fixes at the start and end of each transect.

At it's best, this induces inherent inaccuracy in transect length relying on GPS (although GPS accuracy is at least recorded at each fix). I was wondering if anybody here could think of a solution to record transect length more reliably or a workaround to equate transect length more accurately? Is there a piece of equipment which could be affixed to the rake to measure its distance traveled?

Proper solutions must be able to be operated by a single person while aboard a vessel and be straightforward and quick enough to rival (preferably beat out right) the time it takes to allow for a proper GPS fix and manual recording of coordinates.

The easiest and larger improvement in accuracy you can implement is switching from the non-differential single frequency GPS measurement to a double frequency and/or differential GPS measurements. That usually takes down the error of single measurements from a few meters to a few tens of centimetres or less.

The GPS systems that are within cell phones, tablets and most ships calculate their position standalone and in real-time using only one of the two civilean frequencies that the GPS satellites broadcast. The greatest source of error of those measurements are the discrepancy between the atmospheric and ionospheric models and the reality.

There are two workarounds to this problem, both often used simultaneously to get even better results.

The first workaround, is two use more sophisticated GPS instruments that can record the two civilian frequencies that the GPS satellites transmit. As each frequency is refracted by the atmosphere in a different way, the GPS can better calculate its effect and correct for it.

The second workaround is to do differential measurements. That is correcting the measurements of your GPS based in the errors recorded at the same time by a nearby GPS station at a fix known position. That is call a base station.

You can install your own base station on the ground near the area you work, or use one from the international network of base stations.

My recommendation, would be that you buy a double frequency GPS. If cost is a constrain, go for an used one on e-bay and you can get an excellent quality GPS for just a few hundred dollars. Then you put that GPS to record while you do your transect and it will generate a file with raw GPS measurements. Then, later, at home you upload that file (maybe after a format conversion) to a free GPS processing service and you will get back a file with the GPS track with MUCH better accuracy than your handheld GPS.
This would be equivalent to use the first workaround I described and the processing I'm suggesting here is called PPP (Precise Point Positioning).

When you record the raw GPS data and do the processing later is called post-processing, and it is the best practice if you don't need the high accuracy measurements in real-time. After a week or so, the DoD issues high accuracy corrections of the positions of the satellites and their internal clocks. So if you wait for this high accuracy corrections you can get better precision than any real-time processing. All this is already embedded in those free online processing systems. So you just need to wait a week, upload your file and wait for the result.

The next step would be to have a second GPS and set up your own base station (or check if you work reasonably close to an existing base station). However, my guess is that the gain in accuracy won't make much sense given the errors in the relative position between your GPS and your bullrake.

A second different approach would be to equip your bullrake with some sort of distance measuring wheel, that rolls over the sea floor and records the distance traveled by the bullrake. But it might be significant technical challenges to make such a device work reliably.


Material used in river embankment and difference between levees and dykes What is the difference between levees and dykes in terms of river embankment and also which type of materials are generally used in making river embankment ?

Generally, the terms are used somewhat interchangeably. However, a levee can be formed along a river or ephemeral channel due to natural causes. Mainly: flooding of the river/channel and subsequent deposition of suspended material on its banks. In case of a river: as this occurs on the sides of the river where the flowing water has the least energy, it mainly carries fine material such as fine sand, silt and clay. A dyke, on the other hand is often man made and can consist of numerous materials. In the Netherlands for instance, it is often made of various components of sand, clay and peat.

As the description in the image is dutch, the yellow parts are sandy materials, the brown/reddish are clayey materials and the orange/pink materials are peaty or clayey. You will often find peaty and clayey material on the outer parts of a dyke. These materials conduct less water than sand and serve as a first protective layer. In the Netherlands, the core is often made of sand, as the stability and geotechnical behaviour of sands are less influenced by water than those of clay. Clays shrink and swell as a result of water content, in extensive drought this may cause clays to crack and dykes to be damaged. Additionally, sands are more easily drained than clays, as a result of their bigger pores.
Sources:
Deltares


What's the diference between claystone ,silt,mud, mudstone ,mudrock, clay ,shale and siltstone? Here in Perú , we call those rocks ; lutita = shale , siltstone = limonita , but as far as I know we don't use the terms claystone and mudstone in spanish terms.

Clastic sedimentary rocks are classified by size of the sediment particles making up the rock.  Particle size descriptions like sand, silt, and clay have specific meaning in geology and engineering. (see chart below).

Shales, mudstones and claystones are rock types that are very similar to each other.

Siltstone - greater than half of the composition is silt-sized
particles.
Claystone - greater than half of the composition is
clay-sized particles.
Mudstone - hardened mud; a mix of silt and clay
sized particles.

The difference between mudstone and shale is that mudstones break into blocky pieces whereas shales break into thin chips with roughly parallel tops and bottoms.

The terms shale and claystone are sometimes used interchangeably.

References:
Mudstones and shales
Fun rock charts on pinterest


Is there sand in Antarctica? There's a song "Blizzard's Never Seen the Desert's Sand". Given Antarctica is a desert, someone questioned the title's validity. BUT is there sand in Antarctica?

I'd imagine yes as it's a pretty basic soil and Antarctica is a big place, and I know there is land mass, not just ice, in Antarctica. I'm not sure though - any more info or evidence about the presence of sand?

Yes. In fact, there are sand-dunes in Antarctica [1:15].


Seeing a varied change in brightness across the landscape during sunrise? In this video of sunrise at Cadillac Mountain, Maine, the landscape closer to the horizon appears to brighten sooner than the foreground. It makes sense to me, the terrain at the horizon is experiencing the sunrise before the terrain at the water level in the foreground. I'm wondering what is the minimum height someone would have to be see the difference in the brightness on the ground in the distance to the brightness on the ground nearby.
For example, if from 200' high one can see at least 15 miles to the horizon, and the sun rises over a minute earlier 15 miles away from the observer, would the observer be able to see a difference in the brightness of the two locations?
I'm assuming a latitude of 50°N.

TL;DR: It certainly is possible from a geosynchronous orbit, an altitude of 35786 km. It is also possible from a very high altitude weather balloon.

A key issue is that the terminator is not a line. Thanks to the Earth's atmosphere, the terminator is instead a band that is about 1000 km across that gradually transitions from sunlit to dark. At most latitudes sunlight notably  starts to decrease at least 10 minutes before sunset, but one can continue with outdoor activities for a half hour or more  after sunset. (The reverse is true for sunrise.) That 40 minute period or longer time span corresponds to a very wide band. Even an SR-71 could barely have seen that ~1000 km wide band that transitioned from sunlit to dark.
In addition to barely being high enough, another issue with an SR-71 was that they moved so fast. Something that flies even higher than did an SR-71 but flies much, much slower than an SR-71 is needed. That would be a high altitude weather balloon. A high altitude weather balloon (30 km or higher) could see both the bright and bright sides of that 1000 km band, and it could see that band slowly moving.
Even higher up (much higher up), that widish band doesn't look at that wide from the perspective of a geostationary satellite. Now it does looks a bit like a line. Just as is the case with a geostationary high altitude weather balloon, a geostationary satellite would be able to see the terminator (now a line rather than a band) move over the more or less stationary Earth.


Groundwater unloading and corresponding changes in fault zone stick-slip behavior I was intrigued by this Slate piece, more or less a summary of Amos et al. (2014)'s Nature article, which essentially states that groundwater depletion and subsequent crustal unloading causes a decrease in the stress normal to the San Andreas fault, thus bringing the fault "closer to failure" (to quote from the abstract).

Does that mean, as Eric Holthaus, the author of the Slate post suggests, Amos and his co-authors believe that due to the drought, the next "major" earthquake may not be quite as significant in magnitude? (The idea being that an increase in small-magnitude slip events over several years will help ease the intensity of short-period rupture propagation during a larger event?) Or, does it mean that the released stress is just being redistributed to locked sections of the fault system, which I assume experience decreased Mohr–Coulomb forces due to the region wide groundwater draw down? Elsewhere in the Slate article, for example, Holthaus notes that the August 2014 Napa Earthquake actually redistributed some of its released stress onto the Hayward Fault, which doesn't quite seem to support the "easing" hypothesis.

Am I wrong in thinking that the two ideas referenced (easing vs. redistribution) might be mutually exclusive? I sort of wish Holthaus had delved a little deeper in his analysis, since it seems that the clarity of the Slate article takes a fair hit from this inconsistency.

Changes in water level effect the pore pressure at depth around the fault. The general assumption is that the pore pressure is proportional to fault-normal stress which can be thought of clamping stress (i.e., the stress that prevents it from slipping). Basically the higher the clamping stress the more shear stress is required to make it slip. Now the shear stress on San Andreas accumulates due to plate motion between the North American and Pacific plates and that rate remains unchanged. But the normal stress can change slightly due to water level changes, so it can either advance or retard the occurrence of an earthquake in time. But under no circumstances can it stop them from occurring.

The main idea in the paper is that the normal stress on faults have slightly decreased (due to water level drop) which helps to unclamp the fault(s) which in turn increases the background seismicity rates.

So given all this, the first argument by (Holthaus) is correct. However the unclamping can also advance (in time) the occurrence of the big one. Having said that please remember that stress changes we are talking about are rather small.

With regards to the Napa earthquake: The point of an earthquake is to relive the accumulated shear strain. If there are two faults in parallel (as is the case in the region) and both are accumulating strain then an earthquake on one will decrease the 'effective shear stress' on the other fault, directly parallel to it. However at the same time it will increase the shear at the two ends. So things are slightly more complicated.


Are Great Britain and Italy parts of the same geological feature? The Great Britain island and the Italy peninsula look somewhat aligned on the map, like continuations of each other.

Are they part of the same large scale geological feature?

No

Great Britain doesn't necessarily have a unitary geological origin, but the mountains on it (such as there are mountains) are well worn left-overs from the Caledonian orogeny of 400 million+ years ago. These were thrust up before the tetrapods even took to land as part of the plate collision that formed the northern half of Pangaea. This is the same orogeny that made the Appalachians in the US and contributed to the mountains of Scandanavia, as well.

The Appenines are a result of the much more recent Alpine orogeny. Caused by the collision of Africa into Eurasia over the last 60 million years or so, this orogeny built mountains from Spain and Morocco to the Zagros and Alborz in Iran.


How does Earth's heat escape to space? I know that if the sun stopped shining, Earth would lose it's heat and we'd all freeze and die. On the other hand, we don't keep increasing temperature when the sun shines because heat escapes to space. But how does the heat leave earth's atmosphere if space is a vacuum and vacuums don't conduct heat except through waves?

How does Earth's heat escape to space?

TL;DR: By the exact same method heat from the Sun escapes into space. Electromagnetic radiation does not require a medium. In fact, electromagnetic radiation works best in a vacuum; no medium is required. Intervening matter has an annoying tendency to absorb electromagnetic radiation. That absorption, in a nutshell, is the greenhouse gas effect.

Earth's heat escapes into space via a complex set of processes. One is convection. Eagles, hawks, and other birds use those rising thermals to get a free ride to altitude. A second mechanism is latent heat. Evaporation of water is an endothermic process, meaning it absorbs energy from the surroundings (this is why sweating keeps you cool). Condensation is an exothermic process. While falling rain cools the surface, the net transfer is upward.

Those rising columns of warm air can only go so high; they only rarely cross the tropopause (the boundary between the troposphere and stratosphere), and that is only in the case extremely unstable of conditions. Latent heat, along with birds, ride those rising columns of air. This brings up a third and the ultimate mechanism by which the Earth's heat escapes into space, which is electromagnetic radiation.

Every object, including the Earth's surface, absorbs and radiates heat electromagnetically. The atmosphere does the same. The atmosphere absorbs most of the electromagnetic radiation emitted by the Earth's surface. (I qualified that with "most" because there is a small window in the thermal infrared that goes directly into space, at least when there aren't clouds.) This absorbed radiation is quickly re-emitted as thermal radiation, but in a random direction.

The heat carried upward by thermals, by latent heat, and by surface radiation eventually does make its way into space as electromagnetic radiation.


Using current technology, is it possible to directly measure magma flow in the mantle? Can a device or radioactive tracer be inserted into a volcanic lava lake, sunk to the mantle, and study the flow of magma within the mantle?

There are many issues I have with your suggestion. How would you distinguish the radiation that your source would emit from other sources of radiation? Also how would you detect the radiation? Where would you place the radiation detector? A detector placed on the surface of the Earth would not detect any radiation from the Mantle because the Crust would absorb the radiation, due to its thickness.

Any device that would be placed in a pool of magma would most likely be melted by the heat of the magma. If the shell of the device managed to survive, the electronics and sensors would be damaged to the point of being inoperable.

If a device were to survive the heat how would the device send signals to the surface of the Earth? Extreme ultra low frequency radio might work, but the source signal would need to be very strong and I don't envisage that being possible for a device dropped into a volcano.

Getting a device to sink into magma would require the device to have a density higher than that of the magma.

Drilling very deep holes to conduct a seismological survey of mantle magma is not possible given that the deepest hole ever drilled was the Kola Superdeep Borehole, drilled by the Soviet Union during the 1970s and 1980s. Its final depth was 12 262 metres - one-third of the way through the Baltic continental crust. Drilling was terminated short of the 15 000 metre target due to the rock temperature being 180 degrees Celsius.

Using electric potential variations within magma to study magma within the mantle would not be possible because the technique requires an antenna to be place in a drilled hole.


Gaps in locations of volcanos (Peru & Chile) The figure below is taken from Reath, K. et al. (2019)

A couple of things can be seen from this representation

Volcanism seems to be strongly correlated with subduction zones, in this case the Nazca plate and South America plates.
There is a significant gap of volcanoes in both Peru and Chile. Which suggests that subduction is not the whole story. There must be something else happening

Question is: do we know what? What is the reason for these gaps?

As you said, the Andean belt is divided into four segments, usually called the northern, central, southern, and austral volcanic zones (NVZ, CVZ, SVZ and AVZ, respectively; your map lacks the AVZ). This has been interpreted as a difference in the angle of subduction. Under the active zones, the subducting plate (called "slab") sinks into the mantle, releasing water, and the hydrated mantle partially melts, a process called "metasomatism". But under the gaps, the slab has a low angle ("flat slab subduction"), so it doesn't sink deep enough to trigger the melting process. There is no partial melting of the mantle under these zones.

Now, why has the slab failed to sink under these zones? This is due to the presence of submarine ridges. Between the NVZ and CVZ, there is the Nazca Ridge. Similarly, there is the Juan Fernandez ridge between the CVZ and SVZ. Those ridges are young, making the oceanic crust less dense, thus more buoyant (usually it is old, dense oceanic crust that subducts). The ridges also make the oceanic crust thicker, thus harder to subduct.

Image source; by Chiton magnificus in 2011 and placed in the public domain.

Two papers if you want to go further:

Volcanic gaps due to oblique consumption of aseismic ridges
Geodynamics of flat subduction: Seismicity and tomographic constraints from the Andean margin


Can the moon shadow angle change? I've got an argument with a mate.

He thinks that the moon shadow angle can change from night to night.

For example, one night, the near side of the moon is half black/white, black side on top, white on the bottom, and he believes that it can change, and another night, be, for example, black section on the left, white on the right, all observable from the same point on the planet.

Is it right?

Yes. The moon is lit by the sun, so as its position relative to the sun changes, so does the angle from which it is lit.

I recommend reading the Wikipedia page on lunar phase for a good overview, some data, and some good references. This diagram from that page more or less sums it up — the bottom row shows how the moon looks from the earth over the course of a lunar month:

Image is CC-BY-SA by Wikipedia user Orion 8.

The angle of the shadow depends on the time of the observation, and many lunar calendars seem to rotate the lunar images (as above). But this one gives a hint to the shifting relative sun position:

Image is of unknown origin, found here. Unclear rights; fair use.


How can I create multi model ensemble from output of 3 CMIP5 models? I have a output of 3 models of CMIP5, they are CCSM4, IPSL and MPI. I have two scenarios RCP 2.6 and RCP 8.5 for each model. I want to know that how can I create a multi model ensemble from these 3 models? Because when I plot different graphs of various  variables, I end up with so many lines. So is multi model a sensible approach? But how can I create a multi model of these models in R? and what is the science behind multi model ensemble of cmip5 models  (because I have seen in many research papers that authors have taken ensemble means).

Suppose I have 3 lines of each model in a graph, and then showing the mean of all lines by ONE line, is that considered as an ensemble?

What is an ensemble?

An ensemble is a set of several model simulations. One simulation of an ensemble is denoted as ensemble member.

A multi-model ensemble is an ensemble created by simulations with several models (e.g. each model is run twice).

Alternatively, one might create an ensemble by performing several simulations performed with one model. Each simulation is disturbed by some noise so that the model produces slightly different result for each model run. We denote each run as a realization. The generation of the appropriate noise is model dependent (the results should cover the natural variability) and a scientific topic itself. Additionally, we might use other initial conditions or different physical parameterizations.

The individual simulations of a CMIP5 model are identified according to the rip nomenclature: rXiYpZ (r: realization; i: initialisation; p: physics; X, Y, and Z are integers), e.g. r12i1p1 or r1i1p1.

It is also explained here: https://portal.enes.org/data/enes-model-data/cmip5/datastructure

Summarizing ensemble simulations

If you calculate the mean of your models runs, you call it the "ensemble mean". If you calculate the standard deviations, you call it "ensemble standard deviation". The "ensemble" prefix just means that you calculated the mean/std.dev./etc. from an ensemble of simulations.

Example: This plot of the 5th Assessment Report of the IPCC (synthesis report of Topic 2 - Future Climate Changes, Risks and Impacts, online version) shows the ensemble mean (solid thick colored lines) and the space covered by the 5% to 95% percentiles (shaded area).

Please have a look here for the caption and more details: http://ar5-syr.ipcc.ch/topic_futurechanges.php#figure_2_1


How are 'Morning Glory' clouds maintained? Reading the Physics.SE question What is the current physical theory of what causes the 'Morning Glory' roll cloud over Northern Australia? (pictured below):

Image source: NASA Astronomy picture of the day 24 August, 2009 of a Morning Glory roll-cloud over northern Australia. The origin and processes are quite well understood.

In the paper linked in the answer: Travelling Waves and Bores in the Lower Atmosphere:
The 'Morning Glory' and Related Phenomena (Smith, 1988), the author expressed an uncertainty in his concluding remarks, which are the basis of this question:

  The structure and origin of northeasterly
  morning glories is relatively well-understood,
  although questions remain about the precise
  mechanisms inhibiting the leakage of wave
  energy to the upper atmosphere, and the
  transformation of disturbances over the land
  during the day when the original wave-guide
  is destroyed by convective mixing.

The italicised portion suggests that some mechanism(s) prevents these effects from occurring, resulting in the roll-cloud persisting.

What meteorological factors maintain the Morning Glory roll-clouds?

These are some of the most recent areal photographs taken of this phenomenon. The Morning Glory clouds are the visible manifestation of atmospheric Internal Solitary Waves (see the schematic in (b) below). They propagate on a sharp interface between a relatively dry layer ambient air above and a layer of sea water laden air pushed in from the night before below. When the moist air rises the cloud is formed above the condensation level and eventually evaporates at the trailing edge of the wave.

In these photographs, the cloud itself appears as a cylindrical shaped core with high vorticity at a height of $500$ m and a $1$ km diameter. They may stretch for thousands of kms while traveling at up to $50$ km/h.

Internal Solitary Waves are stable by definition, they are waves of permanent form which owe their existence due to a balance between nonlinear wave-steepening and linear wave dispersion. Of course in the environment there are several other nonlinearities which could potentially break apart this structure through various mechanisms. However, devoid of other atmospheric forcing these waves can travel thousands of KMs without loosing much energy.

A final point is that these waves are ubiquitous but the thing is that we very rarely can observe them is such glorious ways, so there is nothing that says that the Morning Glory is special as far as stability goes compared to other locations on Earth. It is in fact common for such disturbances to maintain their shape over large distances.

Source: Ouazzani, Zaim R., et al. "The Morning Glory: Flow visualization by Mother Nature." Physics of Fluids (1994-present) 26.9 (2014): 091110.


Why is Carbon Dioxide a Greenhouse Gas whereas Ammonia is not? Why are some gases Greenhouse gases while some are not?
I did search this on the net but didn't get any clearcut/credible answers.
What exactly is the property that is common among Ozone, Water Vapour, CFCs, and Methane that makes them all greenhouse gases?

A molecular gas is a good infrared absorber if it has several atoms (not just 2, like O2 and N2) or if it is hetero-nuclear (e.g. CO and NO).  These type of molecular arrangements allow more infrared energy to be absorbed because there are more vibrational states that are possible.  Yes, ammonia fits that description, but it is not long-lived in the atmosphere and it is not widespread.  So, even though ammonia is a good infrared absorber, it is not an important greenhouse gas.

Ammonia in the atmosphere is very reactive, and will form to make nitrates and sulfates while in solution (e.g. in cloud droplets).  Thus, the atmospheric lifetime of ammonia is short-lived, whereas most important greenhouse gases are long-lived and not reactive.  For global  warming discussion, you would likely associate ammonia with a net cooling effect since the increased formation of particulate (clouds/haze) increases the albedo of the Earth (which scatters light back to space).


Converting glacier volume to mass: what ice density to use? The density of ice is 0.9167 g/cm3 at 0 °C (under atmospheric pressure).

I know of two factors that may influence this (are there more?)

Pressure

The glaciology faq (Common Questions and Myths about Glaciers) at the Alaska Science Center of the  U.S. Geological Survey (USGS) mentions for glacier depth:

  A good guess is that the ice thickness is about one-half of the surface width of the glacier. Although few glaciers have been measured, the measured thicknesses range from a few tens of meters for small glaciers to about 1,500 meters for the largest glaciers in Alaska.

Does the density of ice change significantly with depth?

The Wikipedia article on ice mentions the density of ice increasing slightly with decreasing temperature, and the different phases of ice under pressure, but nothing on density.
Inclusion of air

Googling for pressure ice density the (my) first search finds Density of glacier ice at the International Glaciological Society. This focuses on air in glaciers making the density lower, and concludes that at larger depths we reach that 0.92 limit:

What would be a good average to take?

This is a non-trivial issue. When you look at volume change of a glacier, you typically subtract two digital elevation models to obtain the difference between the two. First, you must differentiate between ice sheets where ice berg calving reduces volume and more ordinary glaciers with melt processes. There are of course calving glaciers as well so it is possible to get into great detail for any one specific glacier, so here I will just discuss the most common case which is a smaller glacier with melt-freeze conditions.

The change in elevation differs in magnitude across the glacier surface due to the movement of the glacier and accumulation-melt processes. The surface material can be (1) glacier ice, (2) snow, (3) firn snow that has survived a melt season) or (4) super imposed ice all with more or less differing densities, you need to assess what sort of material has been removed.

Ice can be approximated by a density of 900 kg/m3, firn has a density of about 600 kg/m3 but it must be remembered that the firn is converted to glacier ice by metamorphic processes so that the density changes with depth from 600 to 900 kg/m3. the transition to ice occurs at depths of about 30 m in temperate glaciers although few studies exist on the actual processes that occur. Snow have very differing densities but considering averages, I would say that it would vary between 350 to maybe 500 kg/m3 for winter (cold) conditions and around 550 kg/m3 for a melting snow pack. Super-imposed ice is closer to ice and probably varies in the upper range of 800--900 kg/m3.

To make matters worse, snow superimposes firn which in turn superimposes ice. This means that in the accumulation area, volume change can result from both a reduction in a snow cover and the firn layer. In the zone near the equilibrium line there can be a loss of both firn and ice. this is also where the superimposed ice will play a role.

So there is no simple density to use since the loss you try to estimate will involve varying types of densities spatially as well as vertically. For annual changes, you can largely ignore the vertical distribution, but with volume changes covering larger periods where climate change influences the longer term location of the equilibrium line and the size of the accumulation area, vertical layering also has to be included.

As a first approximation, a surface zonation of ice snow and possibly firn can be used and perhaps lumping snow and firn with a single density of around 600 kg/m3 can be used. I would, however, say that to some extent any choice you make will be wrong, so being aware of complexity and the limitations is the only way forward.

EDIT:

A couple of useful sources relating to the question:

Huss, M., 2013. Density assumptions for converting geodetic glacier volume change to mass change. The Cryosphere [Open Access]

Moholdt, G., (Referee) Interactive comment on “Density assumptions for converting geodetic glacier volume change to mass change” by M. Huss. The Crypshere Discuss. [Open Access]


What precursor geological activity occurred prior to the Parícutin Volcano eruption in 1943? Parícutin Volcano, sometimes referred to as the 'A Volcano Born in a Mexican Cornfield' (which is also the title of a book published in 1993, more information here), was one of the most well documented and observed volcanic eruptions in the world.

Quite literally, it grew out of a fissure in a cornfield in February 1943, continuously erupting until 1952.

Parícutin Volcano image from the USGS in 1946.  Image source: Oregon State University Volcano World.

What does the evidence suggest for precursor geological processes occurring immediately prior to the Parícutin Volcano eruption in 1943?

The region around the Parícutin volcano is within the Trans-Mexican Volcanic Belt and is affected by the subduction of the Cocos and Rivera Plates (Gardine et al. 2011), as seen in the image below (from Langridge et al. 2013):

As the petrology is very recent, it has provided scientists an unprecedented opportunity to study a complete volcanic sequence. Petrological observations reported by Erlund et al. (2010) determined that there were 3 main distinct phases of volcanic activity, the initial phase, which lasted only about 4 months, is what is relevant to this question.

Erlund et al. (2010) extensively studied the basal tephra, their results suggest the following occurred immediately prior to the 1943 eruption:

magma ascended from depth through dyke and sill systems quick enough to prevent substantial fractionation from olivine settling.
magma was stalled at shallow depths under sufficient pressure to allow plagioclase phenocryst growth.

This magma movement is likely to have caused the ~45 days of seismic activity that was noted before the fissure opened up in the cornfield, initiating the Parícutin volcano eruption.

There is a more modern day analogue to the associated seismicity, based on models developed by Gardine et al. (2011) from an earthquake swarm that occurred near to the Parícutin volcano in 2006, where the low magnitude earthquake swarms occurred in clusters that demonstrated reasonably rapid ascent and lateral movement - suggesting not only a possible mechanism for magma ascent, but also demonstrates the region is still very active.

References

Erlund et al. 2010, Compositional evolution of magma from Parícutin Volcano, Mexico: The tephra record, Journal of Volcanology and Geothermal Research

Gardine et al. 2011, Dike emplacement near Parícutin volcano, Mexico in 2006, Bulletin of Volcanology

Langridge et al. 2013, Preliminary paleoseismic results from the Pastores fault and its role in the seismic hazard of the Acambay graben, Trans-Mexican Volcanic Belt, Mexico, Revista mexicana de ciencias geológicas


Why are deserts mostly located on the western side of continents? I read somewhere in a book that mostly desert found in the western part of a continent.  So my question is that why is it so? I searched on the internet but I didn't get a reasonable answer for that.

Some of the driest deserts on Earth occur in the western side of continents and they are called Coastal Deserts. Examples of such deserts are the Atacama desert (Chile, the driest desert on Earth), the Baja California desert (USA/Mexico), the Namibia desert (southwestern Africa), and the Atlantic coastal desert of Morocco/western Sahara/Mauritania. In mid-latitudes, the western side of continents is most frequently occupied by deserts, while the eastern side tends to be covered by forests (e.g., Amazon rainforest).

. Distribution of non-polar arid regions. Source: USGS.

Coastal deserts occur east of the strongest coastal upwelling regions in the world. The upwelling is associated with eastern boundary currents flowing equatorward (due to Coriolis): the Canary Current (off Northwest Africa), the Benguela Current (off Southwest Africa), the Humboldt Current (off Chile and Peru), and the California Current (western North America). The prevailing winds in these regions are the trade winds that flow parallel to the coast and generate upwelling dynamics: surface Ekman balance is setup (in deep enough waters) with water transport being to the right (left) of the wind in the northern (southern) hemisphere; this causes a deficit along the coast that needs a compensating flow in the deeper part of the water column bringing cold, nutrient rich waters (some of the most productive regions in the world) to the surface.

 Source Commons Wikipedia.

The cold waters near the ocean surface results in a cool, stable coastal atmosphere. In this region, evaporation from the ocean is reduced and produces extremely low rainfall over land. Precipitation is limited to morning fog and produces some of the driest ecosystems on Earth. The Atacama desert is the best example of such environment with average rainfalls of 15 mm/year (the driest non-polar region). In some areas, they are trying to take advantage of the little moisture the fog (Camanchaca) brings to establish some agricultural zones. The fog droplets are too small (1-40 micrometers) to form water drops and precipitate, so they use fog-catchers to collect moisture from the fog.

 Source: newatlas.com


What is the oldest fossil on Earth? What is the oldest fossil ever found on Earth? Where and when was it found? What was the oldest fossil with a brain with 2 hemispheres ever found?

The oldest undisputed fossil are Stromatolites, bacterial mats, the oldest of which are dated ay 3.7 billion years ago. The key term here is undisputed, there are other possible fossils but it is very hard to have certainty with chemical or cellular fossils. The oldest uncertain fossils trace back to 4.28 billion years and are possible bacteria trapped in hydrothermal vent products.

The oldest fossil of a creature with a brain is weird. it is actually several creatures from Ediacaran biota. These are also some of the oldest multicellular life fossils, lacking any hard parts fossilization of early small animals is incredibly rare event even considering how rare fossilization already is. There are several bilaterally symmetrical animals capable of movement, this combined with the fact they are more than two cells thick means they almost certainly had a brain.

Kimberella and Spriggina and their relatives are both almost certainly mobile, with some form of nervous system based on phylogenetic bracketing, others are also likely since the ancestor of chordates may in there somewhere. We know there were moving creatures from the ediacara because we actually have trace fossils that are consistent with a muscular moving organism like anemone.


Why has the Earth's average sea level risen 'only' by nine inches after one degree C increase in temperature? I am only doing gross calculations here, but...
If the Earth has warmed by about one degree Celsius in the last century or so, and the thermal expansion coefficient of water is about .0002085, then the (admittedly salty) ocean should have expanded in volume by about .02%, or 1 part in 5000.  Right?
Well, the average depth of the ocean is about 10,000 feet, and if the water has (mostly) nowhere to go but up, shouldn't the seas have risen by about 2 feet, not .75 feet?
Ummm, I just thought of something...  Has the ocean not warmed as much as the atmosphere?

You should take into account isostasy. As there's more water in the oceans, the crust underneath bends under the weight, creating more room for it. At the same time, continental crust heaves above the oceanic, hence the small value.
A question here to be careful about is where the location of the measuring point, as it very well may not be stable.


How do urban areas affect rain? Urban areas these days can be quite large, and they can have strong effects on the environment: the urban heat island effect being the most obvious, but there may be other, more subtle effects. The relative lack of vegetation and drainage might make them drier, the concentration of high-rise buildings might approximate the effect of small hills, and there's also the air pollution they produce.

Thus I suspect that large urban areas might have an effect on rain, but exactly how? Do they cause more rain or less around them? What about any effects downwind?

In a study conducted in Taiwan Impact of the Urban Heat Island Effect on Precipitation over a Complex Geographic Environment in Northern Taiwan (Lin et al. 2011), found that by observations that

  The UHI effect plays an important role in perturbing thermal and dynamic processes; it affects the location of thunderstorms and precipitation over the complex geographic environment in northern Taiwan.

Hance, the situation and potential models of the distribution of rainfall are further complicated by the surrounding topography.

However, NASA's Earth Observatory page The Impact of City Landscapes on Rain presents 3 hypotheses for urban effects on rainfall, paraphrased below:

As you mentioned, the Urban Heat Island, forms a bubble of warmer air and potentially creates atmospheric instability, resulting in

  as the city-warmed air rises, it cools and forms rain-producing clouds that soak the area downwind.

The buildings and other structures cause a disruption to the ambient air flow, resulting in

  the city’s buildings provide a source of lift to push warm, moist, surface air into the cooler air above it, where it can develop into rain clouds.

Similar to no.2, the buildings split the flow of air around the warmer city, these parcels of air return together on the other side:

  When the two halves of the storm come back together downwind of the city, the air is pushed up like the two colliding trains. The rising air forms rain clouds.

When I did studies of the effects of aerosols (particularly particulate matter) in urban environments, there were many observations to suggest that some particulate matter could potentially become the cloud condensation nuclei that changes cloud cover and hence rainfall patterns.


What type of cloud formation are these dark low-hanging clouds? I was thinking it could have been a non-rotating wall cloud, but I'm not sure.

YouTube video

Picture taken on September 9 2014... between 5-7 pm in North Georgia, about 40 miles north of Atlanta.

Based on your video, it does appear to be a non-rotating wall cloud - but admittedly, it is hard to definitively determine, mainly as it is hard to see any updraft.

Another example of a non rotating wall cloud is from NOAA's Cloud Classification and Characteristics page (image below):

and their description:

  The lowering denotes a storm's updraft where rapidly rising air causes lower pressure just below the main updraft, which enhances condensation and cloud formation just under the primary cloud base. Wall clouds take on many shapes and sizes. Some exhibit strong upward motion and cyclonic rotation, leading to tornado formation, while others do not rotate and essentially are harmless.

Alternatively and given the possible absence of the characteristic updraft of a wall cloud, it could be a scud cloud, similar to the one shown below

Image source

A scud cloud is defined by Accuweather as being:

  ow, ragged and wind-torn cloud fragments, usually not attached to the thunderstorm base. They are often seen in association with, and behind, gust fronts.
  Scud clouds DO NOT produce severe weather. Scud clouds are often mistaken for wall clouds and tornadoes, especially when attached to the thunderstorm base.

A handy tip to tell the difference between a wall cloud and a scud cloud is (according to Accuweather):

  to watch their relative position with respect to the rain area: scud
  clouds move away from the rain area while wall clouds maintain the
  same relative distance.

A video tutorial is included in the Accuweather site


Reisdual soil and the atmosphere influence My text books says that the residual soil shows a similarity in its chemical composition to the original rock beneath it, and that the degree of similarity differs by differing the influence type of atmosphere

I don't get the part of "differing the influence type of atmosphere." Do you have any ideas?

If you are including the early history of the earth, study of regolith from the Archean period has been used to indicate the oxidation state of the atmosphere. Different weathering products form, depending on the amount of oxygen in the air and dissolved in infiltrating rainwater. So the residual soil chemical and isotopic composition changed when the atmosphere became oxic. There are a few locations in South Africa, Canada, and probably other places where these soils were buried and preserved, (e.g. by lava flows near Flin Flon Manitoba Canada).


Why there are no sharp corners in nature? I have read some articles explaining why rounded corners are more aesthetically pleasing, like this one and it all makes perfect sense but my question is:

Why does nature not have sharp corners? What is the law or set of laws that governs this behavior?

The premise of your question is entirely wrong. There are many examples of sharp corners in nature, the most obvious being well formed crystals.

Pyrite is a classic example that was mentioned by @wienein in the comments. In a ideal situation it forms cubic crystals with sharp edges.

A classic non-crystalline example would be volcanic glasses such as obsidian, which fracture to produce extremely sharp edges and were historically used by some cultures for making blades and other sharp tools.


What's the official reason why it became so hot in the Kola borehole? The Kola drill went 'only' a third the way to the mantle, so its deepest point was still closer to the surface than to the mantle. Why did the drillers experience 180 deg Celsius when so deep, where did that heat come from? Logically I'd expect it would get colder the deeper you went into the crust (until about halfway to the mantle I guess where temperature started rising again), not hotter.

Unfortunately, you intuition about subterranean ground temperatures is incorrect.
Basements and cellars do provide cooler conditions to store perishable items because the near surface rock insulates against surface heat.
Go deeper however and temperature increases. Near the Earth's surface, within the crust, and away from tectonic boundaries, the rate of temperature increase, due to the geothermal gradient is  25–30 °C/km. The geothermal gradient increases with depth.

Most of the heat is due to the decay of naturally radioactive elements,mostly within the mantle.

Heat flows constantly from its sources within Earth to the surface. Total heat loss from Earth is estimated at 44.2 TW.


Factor 1000 in mixing ratio formula I am seeing two different formulas for the mixing ratio, which differ by a factor 1000. To be more specific:
$w = 0.622 \cdot (e/p)$
and
$w = 1000 \cdot 0.622 \cdot (e/p)$
where $e$ and $p$ are the water vapour pressure and the atmospheric pressure, respectively.
I assume the factor 1000 has to do with the fact that the mixing ratio is theoretically a ratio of masses, so probably the numerator can be expressed in grams and has to be converted to kilograms, but I'm confused because I don't see masses in these formulas.
What's the difference between the two ?

The factor of 1000 may be related to the expected units. The mass 'units' can be found in the derivation.
The full derivation of mixing ratio goes like this
$$w=\epsilon\frac{e}{P}$$
since, by the ideal gas law,
$$e=\rho_vR_vT$$
and
$$P_d=\rho_dR_dT$$
then the mixing ratio is expressed as
$$w=\epsilon\frac{\rho_vR_vT}{\rho_dR_dT}=\epsilon\frac{\rho_vR_v}{\rho_dR_d}$$
Since $\epsilon=\frac{R_d}{R_v}=0.622$ (see above hyperlink),
$$w=\frac{\rho_v}{\rho_d}$$
To return back to the question 'what is the difference between your two equations?' The units reported are $g/g$ and $g/kg$ for the first and second equations, respectively.


How many $\ce{^{14}C}$ measurements have been made? I know that the upper limit of radiocarbon dating is typically about 60,000 years, but how many radiocarbon dates have actually been measured? As of October 2015, how many $^{14}\ce C$ (radiocarbon) measurements have been made worldwide, how many have been calibrated by historic dates, and what proportion of measurements have yielded inconsistent results?

How many have been validated by historic calibration, and what
  proportion (if any) yielded inconsistent results?

Often with an item that they want tested, a specific date isn't available so calibration isn't possible, but calibration can be done when dates are known.  Tree rings are most common and (though I've not read of this being done), samples from dead bodies from a specific battle or disease outbreak where a date of death is known.  Article here and here.

The calibration curve represents changes in the amount of C-14 present in the atmosphere which is also a factor.   There wouldn't be a charted curve if calibration hadn't been done quite extensively (see 2nd article above).

There's some room for bacterial or other contamination, especially with older objects, and contamination has lead some inconsistent results but that's not because the theory isn't sound but because of miss-handling.


Why don't iron meteorites on Mars rust or oxidize? Why are they shiny? Wikipedia's WikiNews' 2005 article Mars Rover’s Basketball-Shaped Discovery Stirs Controversy says:

  The surface of the meteorite was found to be remarkably free of corrosion. Researchers are as yet unsure whether this means it arrived recently or that it has possibly been sandblasted thoroughly.

and links to Space.com's Mars Rover's Meteorite Discovery Triggers Questions

On earth we don't normally see clean, shiny iron surfaces because iron is easily oxidized in a short time even at room temperature by several oxidizing components of air. Some of these are present on Mars but of course at far lower in concentration, but there are other oxidizers including perchlorate. Yet both iron meteorites discovered on Mars that I'm aware of (Heat Shield Rock and Egg Rock) look clean as do others shown in that Sky & Telescope article.

Is it known why? Have they landed so recently that oxidation hasn't had the time to make much change, or are they sandblasted clean as Karen Steele's character Eve McHuron told Kirk one of the miners to do with a dirty cast-iron skillet† on the storm-plagued planet Rigel XII.

Photos of these two meteorites taken by Curiosity can be seen in

this answer to What is the name of meteoroids which hit Moon, Mars, or pretty much anything that isn’t the Earth?
this answer to Who discovered “Egg Rock”? The Curiosity rover or people?

Also see Curiosity Finds Iron Meteorite on Mars

†from this answer

tl;dr: Compared to Earth, the atmosphere on Mars is very thin; in addition, it contains much less of oxygen and water (i.e., is very dry). It is much colder there. These conditions may slow down oxidation to an irrelevant rate.

For an object of pure iron, note that according to the English Wikipedia about Mars:

  "The atmosphere of Mars consists of about 96% carbon dioxide, 1.93%
  argon and 1.89% nitrogen along with traces of oxygen and water."

This contributes as plausible contribution for a lesser rate of oxidation than on earth because the concentration of an oxidizer (i.e., oxygen) is much lower (0.146 vol%, according to the side table, ibid.)  if one assumes absence of processes splitting the $\ce{CO2}$ to yield oxygen.  To set these values into context (entry Earth):

  "A dry atmosphere is composed of 78.084% nitrogen, 20.946% oxygen,
  0.934% argon, and trace amounts of carbon dioxide and other gaseous molecules. [...] Water vapor content varies between 0.01% and 4% but averages about 1%."

Equally note that the reported surface temperatures on Mars (min 130 K, mean 210 K, max 308 K) are substantially lower, than on Earth (min 184 K, mean 287.16 K, max 330 K) -- equally slowing oxidation.

About water and atmosphere humidity:  Provided the meteorites get water wetted, said perchlorates could start to work as oxidizer of iron.  In comparison to this, dry perchlorate will remain inactive.  Again, Mars' atmosphere (0.0210 vol% of water vapour, ibid.) seems to be considerably more conservative than Earth's.

You can't have oxidation alone, it is a electrochemical process where some other material in contact with the one oxidized has to be reduced. Corrosion of the meteorites equally could occur if these simultaneously contain grains of metals / alloys differing in the their electrode potential provided

these grains  were in close contact with each other, especially if their grain boundary were water wetted, and
if one of the metals / alloys -- relatively speaking -- would be «less noble», i.e. a material with a more negative reduction potential, than any other grain / material in contact.  The less noble grain than would become a galvanic anode and eventually be "eaten away", protecting the other, more noble one, to be oxidized.(table)  The formation of these little, local electrochemical cells could be even more important if there were salty water droplets on the surface at room temperature and above accelerating corrosion.  (This, by the way, a reason why steel bridges and copper house roofs exposed to the climate and atmosphere of salty seas are more prone to galvanic corrosion than similar constructions only exposed to fresh water.)  Presence of phosphates in said meteorites however could slow down the oxidation of the meteorites (passivation, as assumed for the Iron pillar in Dehli).

Note: The initial answer assumed iron meteorites to contain discrete grains, occasionally altogether with grains of other metals.  A comment by@KenFabian pointed out iron meteorites however mainly consist of (Fe,Ni) alloys.  Their electrochemical properties may be different to their components (e.g, table), which the edit aims to include.


A balloon falling from space? How long would it take for a store bought rubber balloon filled in space with air to fall from space just outside the atmosphere and touch ground? Would it Pop?

Added after comments: Ideally you would like to have a balloon filled with 14 PSI before it was dropped so that way it maintains its shape all the way down to the ground. But being a normal party balloon has its problems. It would only take one PSI of ambient air to fill a party balloon in space and any more than that it would pop.
I didn't take in consideration on how temperature would affect the rubber. On the sunny side it would be well above the melting point of the rubber. On the freezing shadow side of the Earth side the rubber would freeze becoming brittle and break.

Temperature outside would the pressure of falling through the atmosphere pop the balloon?

You cannot leave "temperature outside", as temperature is the key factor to know if the balloon would pop or not.

Let's set up some assumptions about the problem so we can calculate something:

The gas inside the balloon behave according the ideal gas law: $PV=nRT$
That the balloon can hold a differential pressure of 30 mmHg (=4000 Pa) as found in this experiment.
That the maximum volume of a balloon is 0.015 m$^3$ as suggested here.
The balloon starts filled to its maximum size.

With this we can calculate how many moles of gas the balloon can hold when inflated in space at a given temperature.

For the temperature I'll assume it will be something between the temperature of the cosmic microwave background radiation (if it is on the shade) of ~2.7 K (-270 °C), and the temperature that a black body that is illuminated by the Sun near Earth's orbit, which would be about 278 K (about 5°C). This assumes that the balloon is small enough so that heat can be transferred efficiently by diffusion from one side to the other (the calculation of this value can be seen in the code at the end and is based on the equation here).

With this range of temperatures we can find the volume of the balloon on the surface assuming a final pressure of 1 atm (101325 Pa) and a temperature of 15 °C.

We get the following relationship:

In red are the final volumes for which the balloon would explode and in blue when it wouldn't. The critical temperature in between is -262 °C (~11 K).

Therefore, the balloon would not pop as long as its initial temperature is higher than -262 °C.

This also assume that the hottest point in the trajectory is the surface. This means that we are assuming that the balloon will pass through the thermosphere fast enough to do not reach thermal equilibrium with it (it can be extremely hot). This could be a reasonable assumption given the very low density of that layer.

Of course this also assume the rubber of the balloon do not change its properties with temperature.

So, only once you specify the height at which you release the balloon and its initial temperature, then you can start calculating fall time. And that will be more difficult, because even if you assume the balloon is at free fall terminal velocity the whole time,  this velocity will change along the fall line due to changes air density and balloon size. Air density and balloon size will affect air resistance and, therefore, terminal free fall speed. You will need to do an analytical or numerical integration of the fall to get the total time.

Matlab code used to generate the above figure

R=8.3145;%Ideal gas constant [J/mol K]

Lsol=3.828e26;%Solar luminosity [W]
Dsol=149597870700;%Distance earth-sun [m]
sigma=5.670373e-8;%Stefan–Boltzmann constant [W m^-2 K^-4]
alpha=0;%albedo
epsilon=1;%emissivity
% Temperature of a black body (rotating or small enough to transfer heat efficiently from the illuminated side to the dark side)
Tbb=((1/4)*((Lsol*(1-alpha))/(4*pi*epsilon*sigma*(Dsol^2))))^(1/4);

% Temperature range
T=linspace(2.7,Tbb,1000);%[K]
Vmax=0.015;% Exploding volume [m³]
Pspace=4000;%Maximum pressure hold by the balloon [Pa]
n=Pspace*Vmax./(R*T);% number of moles that the balloon would hold
Patm=101325;% Atmospheric pressure [Pa]
Tsurface=15+273.15; % temperature at the surface [K]

% Volume once back on earth surface
Vfin=n*R*Tsurface./Patm;

explodeIdx=Vfin>Vmax;
Tlim=find(explodeIdx,1,'last');

figure('Color','w');
hold on
box on
plot(Vfin(~explodeIdx)*1000,T(~explodeIdx)-273.15,'b','LineWidth',2);
plot(Vfin(explodeIdx)*1000,T(explodeIdx)-273.15,'r','LineWidth',2);
plot([0 max(Vfin)]*1000,[1 1]*T(Tlim)-273.15,':r','LineWidth',2)
ylim([0 max(T)]-273.15);

xlabel('Final volume [liters]')
ylabel('Initial temperature [°C]')


Units of wave spectrum In ocean spectra such as the Pierson Moskowitz or the JONSWAP models, the units of $S(\omega)$ are $m^2/(rad/s)$ (or whatever unit of measurement you are working in). Where does the $m^2$ come from and what does it mean physically?

I understand that the integral of the spectrum over all frequencies, i.e. $\int S(\omega) \,d\omega $, is the variance which means that the integral should have $m^2$ units? Please correct me if I am wrong.

I understand that the integral of the spectrum over all frequencies is the variance which means that the integral should have $m^2$ units? Please correct me if I am wrong.

You are correct. If elevation $\eta(t)$ is the measured quantity (units of $m$), the Fourier transform of wave variance $\eta^2$ yields spectrum $S(f)$ with the units of $m^2/Hz$, or if you are working with angular frequency $\omega = 2\pi f$, it yields $S(\omega)$ with the units of $m^2/rad/Hz$.

More details can be found in the answer to this question.


Do fluctuations in radioactive isotope decay rates affect carbon dating techniques? In 2010, Purdue University published a research paper[1] stating that their researchers had detected slight fluctuations in radioactive isotope decay rates "in synch with the rotation of the sun's core." The article also stated:

  The team has not yet examined isotopes used in medical radiation treatments or for dating of ancient artifacts.

Has there been any further research on this, and has it been found to affect carbon dating techniques or other archeological dating methods? Are the fluctuations large enough to call into question currently accepted geological dates?

http://www.purdue.edu/newsroom/research/2010/100830FischbachJenkinsDec.html

First off, the purported variations were reported to be cyclical. So the net effect on archeological dating would be null even if these variations existed.

Secondly, these purported variations are very dubious. Scientists are not immune from "crackpot syndrome". If anything, scientists are more susceptible to this than the average public. There's a bit of a crackpot lurking in every good scientist. Their job, their very being, is tied up in pushing the boundary of human knowledge. Very good scientists listen to their inner crackpot but keep it inside until they are very sure that their inner crackpot has revealed something new. Not so good scientists regularly expose their inner crackpot for the whole world to see.

What this means is that when you read some extraordinary claim you should be extraordinarily suspicious, at least at first. They might have found something, then again, they might just be exposing themselves.

In this case, I suspect the latter. What I suggest in the case of extraordinary claims: Go to a site such as scholar.google.com and search for the journal article in question. Scholar gives a citation count (oftentimes inflated, but that's a different story). Click on it and you'll get a new page that lists the articles that cited the article in question. In this case, you'll see that there have been a paltry 25 citations in the 8 years since the article was published. That alone is very noteworthy. This article that you think is significant is anything but.

If you dig deeper, you'll see that almost all of those 25 citations are self-citations, subsequent articles by one or more of the original authors who have cited their own work. That makes this article even more suspicious. If you filter out the self-citations, you'll see that the original list of 25 citations dwindles down to two or three, and most of those say "There's nothing to see here. Move along, move along."


Has recent drop in airline flights over the US had a measurable warming effect as was found after 9/11? I recall that after 9/11, when all US flights were canceled, there was a statistically detectable bump in average temperature. Something about jet contrails disappearing for 4 days. Has anything like that happened during the recent COVID-19 drop in US air traffic? Sorry I don't have the reference to the 9/11 data/story.

It's not clear yet; this is an area of active research which it itself hampered by COVID-19 social distancing requirements, according to this report on Climate Change News:

  Scientists with Nasa and European research groups hope to use clear
  skies to narrow down massive uncertainties about the warming effect of
  condensation trails – the wispy white lines that criss-cross the skies
  in the wake of jets engines.

  “The air traffic system has not been diminished to the current levels
  since the days following 9/11,” said Patrick Minnis of Nasa Langley
  Research Center, who is joining a research effort to study
  high-altitude clouds.

  “Flight groundings at the scales initiated in response to the
  coronavirus pandemic are a significant opportunity to better quantify
  the impact of air traffic on cloud cover via contrail formation.”

As to the post-9/11 effect:

  The new research builds on studies after the 9/11 suicide hijackings
  in the US grounded flights for a few days. One study, for instance,
  found that the plane-free skies had an impact on temperature
  variations in the United States, but some researchers say the findings
  might have been caused by natural variations.