Why is this area colder than the surrounding hotter area? I was looking at this website and surprised to see that a cold area is surrounded by much hotter area. My understanding is that from the equator the more north/south direction one goes, the colder area one would encounter.

But why this colder place is surrounded by hotter area?

The Himalayas and the Tibetan Plateau have high elevation and temperature drops with altitude up until the tropopause. The temperature on the map is measured and modeled on the land surface, regardless of elevation. You can also see that the temperatures in e.g. Ethiopia and the Caucasus Mountains are lower than surrounding lowlands.

At latitudes around 30 degrees (north and south), the air is dry and hot due to global circulation pattern. The weather patterns are also controlled by the topography, humid air can't pass the mountain range as it's forced to an altitude where the temperature force it to condensate. That is why the Gobi desert is hot and warm in the summer.

I hope this answers your question.


Where I can find high-res public domain images of Countries or Continents on the web I found this one of Africa:

That one is nice because it's > 3000x3000px which is large enough. I have looked around a bit for ones of these countries but haven't found anything that is large/high quality, free/public domain, and free of clouds/weather like the Africa image:

United States
Russia
China
India
Mexico/Central America
South America
Canada
Greenland/Iceland/Arctic
Europe
Australia
Southeast Asia
Japan

I would like to find these broad areas as images on a high quality satellite image similar to this Africa one.

You can find satellite images free of clouds at chinesse version of google maps.

Under the rigth toolbar, top icon, you need to uncheck the first layer with the geographical names and click on the satellite image button, and you can place the view to see maps as this one of Southamerica.


Tipping bucket rain gauge measurement, normalizing I have bought this cheap rain gauge (only the rain gauge, not the other parts) for measuring rainfall with a Raspberry Pi. It works as far as I can tell, every bucket swing will result in an interrupt that I can further process.
The datasheet is located here and this is where my questions begin:
I have calibrated the device and found that around 1.2-1.3 mL will tip the bucket. Now rainfall is usually measured in mm/m², so the datasheet also covers this: 0.2794mm per contact. Now how do I get this to a measurement in mm/m²? The area of the rain gauge is about ~0.0055m² (11x5cm). Is it safe to assume that the rainfall is the same in this m²? So if I measure 5mm of rainfall, then it's also 5mm per m²?
Hope that was not too complicated in my explanation.

mm per square meter is a measurement of volume, it's not really a depth divided by an area. You can tell as much because if you have 1 mm per square meter and you increase the coverage area to 2 square meters, the depth doesn't change---the volume increases. You just need to convert your volume measurement.
$$
1.2 mL = 1.2 cm^{3}
$$
1.2 cubic centimeters is equivalent to a 1.2 cm depth over an area of 1 square cm.
$$
1.2 cm = 12 mm
$$
$$
1 cm^{2} * \frac{1 m^{2}}{100^{2} cm^{2}} = 0.0001m^{2}
$$
12mm per 0.0001 square meters is not a useful metric. You have to obviously make the square meters 1 square meter, but you have to be careful. When you increase the area, the depth will necessarily decrease (because the volume has to be equivalent). Multiplying the area by 10,000 square meters per square meter will give you 1 square meter; subsequently, the depth must be divided by the same amount.
$$
\frac{12mm}{10,000} = 0.0012 mm
$$
So you have 0.0012 mm per square meter with each tip of the rain gauge. We can check our work by converting it back to a normal volume.
$$
0.0012 mm * 1 m^{2} * \frac{1000^{2} mm^{2}}{1 m^{2}} = 1200 mm^{3} = 1.2 mL
$$
As a side note, here is a useful tool provided by the United States Geological Survey for converting depth per area measurements to equivalent volumes:
https://water.usgs.gov/edu/activity-howmuchrain-metric.html
Edit
Going back to the depth given by the data sheet, I ran the numbers and
$$
(0.2794mm)/(1000mm/m)*(0.0055m^2) \approx 1.54 mL
$$
which about matches the volume you have. So if you want the depth for one square meter, you just have to multiply the area by the factor of $\frac{1m^{2}}{0.0055m^{2}}$ and divide the depth by the same factor. So essentially you want to multiply the depth by the catchment area of the gauge.
$$
(0.2794 mm) * (0.0055 m^2/m^2) = 0.00154 mm
$$
as the depth for 1 square meter.


What proportion of the energy input to the ocean tide system comes from the sun? The earth's ocean tides are primarily driven by the moon, but also by the sun. The relative strengths of the related tidal constituents varies from place to place across the globe. But what is the proportion of the energy entering the global system from each?

From [1, 2], the oceans are dissipating about 3.5 TW of energy. The moon and sun input about 3.2 TW and 0.5 TW, respectively. (0.2 TW of the 3.7 TW are dissipated by the solid Earth and the atmosphere.) Another estimate of tidal energy dissipation [3], looking at the 8 major tidal constituents, estimates 0.411 TW of solar tides dissipated by the ocean. (With an additional 0.03 TW dissipated by a moon-sun interaction constituent.)

[1]: Munk and Wunsch, 1998, https://doi.org/10.1016/S0967-0637(98)00070-3

[2]: Jayne and Laurent, 2001, https://doi.org/10.1029/2000GL012044

[3]: Egbert and Ray, 2003, https://doi.org/10.1029/2003GL017676


Where did the atmosphere's nitrogen come from? According to Wikipedia's article Atmosphere of Earth:

  Outgassing from volcanism, supplemented by gases produced during the late heavy bombardment of Earth by huge asteroids, produced [Earth's second] atmosphere, consisting largely of nitrogen plus carbon dioxide and inert gases.

However, it doesn't explain any further than that. Where exactly did the nitrogen come from? Was it already gaseous or was it in the form of compounds that broke down releasing N2 gas?

There was some free nitrogen in the secondary atmosphere, and also some ammonia (NH3). Ammonia is present today in the atmospheres of Jupiter, Saturn and other gas giants in the outer solar system. The main constituent of the Earth's primeval atmosphere was carbon dioxide, which also makes up the bulk of the atmospheres of Venus and Mars. The ammonia eventually decomposed into nitrogen and hydrogen.

When we look at the atmospheres of Mars and Venus, we see that they contain only 3 percent nitrogen, while our atmosphere contains 78 percent. The main reason for this is that Mars and Venus still retain most of their primeval CO2, while Earth's has largely disappeared because of biological processes (coal,limestone etc). The atmosphere of Titan also contains a massive percentage of nitrogen because competing gases, apart from methane, have mostly disappeared, frozen out by the intense cold

We also need to consider outgassing from volcanoes. These emissions consist mainly of CO2 and water vapour, but there are small amounts of nitrogen and ammonia, and other gases as well.


Intuitive explanation of precipitation amount I'm trying to learn how to make sense of numbers in a forecast. I can interpret temperature and wind speed, but I don't know what to make of rainfall. What does it mean, for a human, that there will be (for example) 0.5mm precipitation? Is it a lot or not? Is there a reference online describing precipitation amounts in everyday terms? I've been looking for something like that, but found nothing, only formal definitions of measurement.

It literally means that the water depth will be 0.5mm. For example, if you place a container under the rain and it fills up to 0.5mm, then the precipitation is 0.5mm.

Despite the fact that a wide container requires more rain to fill up than a narrow container, the larger surface area allows it to collect the right amount of rain water to fill up to the same amount as the narrow container in the same amount of time (as long as the walls are vertical). Therefore, if the rainfall is 1 mm, every square meter receives 1 liter of rain water.

Addendum:

By the way, tuna cans can be distributed along your lawn to serve as a very primitive, but very cheap measurement tool that you can use to create a spatial map of what your irrigation system is doing. You can use that for troubleshooting your efficiency, 1 full can is 1 inch irrigation/rainfall.


What exactly are enantiotropic and monotropic polymorphic transitions? Recently, I've been studying the subject of polymorphism and met two important concepts, the monotropic and enantiotropic polymorphic transition types. However, I can't really seem to grasp the difference between them practically.

What I do understand is that enantiotropic polymorphism is reversible, but what does "reversible" mean practically?

Also, the definition for monotropic polymorphism says that it is irreversible due to metastability. But what exactly is metastability, what does it mean practically? Also, what does "irreversible" mean? Because, surely, I can transform diamond into graphite and graphite into diamond despite it being a monotropic polymorphism.

Thanks in advance for any insight given!

If you can get your hands on a copy of Fegley's book Practical Chemical Thermodynamics for Geoscientists, he gives a good description in Chapter 07, which I'll summarize here.

An enantiotrope is a polymorph that undergoes a reversible transformation into another polymorph at atmospheric pressure. If you're not familiar with the concept of reversibility you may want to read up on entropy, spontaneity, and the 2nd law of thermodynamics. Briefly, a reversible transformation is a process in which the system and surroundings are in equilibrium at all times. An important property of these processes is that $\Delta$ S$_{universe}$=0. Reversible processes don't actually occur in nature but they can make good approximations for some things we observe.

A monotrope is a polymorph that does not have a reversible transformation into another polymorph at atmospheric pressure. One polymorph is always stable and the other is metastable. Monotropy exists in systems where the transition temperature between solid polymorphs is above the melting point of the lower-temperature polymorph. In many cases, upon heating the metastable monotrope melts, then resolidifies to the stable monotrope, which melts at a higher temperature.

Metastability refers to a nonequilibrium state that is approaching equilibrium slowly enough that we can say it's stable over a given period of time.


Relation between Magnitude of Greenhouse Effect and the Concentration of GHGs like $CO_2$ The Average Surface Temperature of the Earth is calculated by the following equation:
$$\sigma T_s^4=\frac{(1-A)\Omega}{4}+\Delta E$$
where,
$\sigma$= Stefan-Boltzmann Constant
$T_s$= Average Surface Temperature of Earth
$A$= Global Albido
$\Omega$= Total Solar Irradiance
And, $\Delta E$= Magnitude of Greenhouse Effect
The observed average surface temperature of Earth is about $288K$, Global Albido as seen by satellites is about $0.3$ and the total solar irradiance is about $1370W/m²$. Putting these values in the above equation, $\Delta E$ comes out to be about $150W/m²$.
Now, according to this
PDF I found online, the concentration of $CO_2$ is related to $\Delta E$ by the following equation:
$$\Delta E=133.26+0.044[CO_2]$$
When we put $\Delta E=150$, we get the $[CO_2]=380$ which is the actual concentration of $CO_2$ in the atmosphere according to some online sources in ppm. So the above relation seems correct.
How was this relation calculated? And, how to calculate such relations for other Greenhouse gases, such as $H_2O$?
In other words, given the Equation:
$$\Delta E=x+y[H_2O]$$
Find x and y.
What I noticed: The coefficient of $[CO_2]$ in the above mentioned equation is $0.044$. And, the molecular mass of $CO_2$ is $44.01 amu $. So, Molecular mass might be involved in the calculation of $y$.
My approach: I focused on finding $y$ as $x$ can be calculated later from the same equation since $\Delta E$ is known and concentration of $H_2O$ should be available online. According to my understanding of the Greenhouse effect, $y$ represents how much energy per unit area does $1$ $ppm$ of a $GHG$ can trap and transmit down to Earth. I tried searching online for some data on the same, but could find none.
Please throw some light on the topic.
Thank You.

Δ=133.26+0.044[2]

It’s just a numerical coincidence that the 0.044 looks like the molar mass of CO2.  That equation gives 0.044 * 380 = 16 W/m2, which is the reduction in surface downwelling IR if you remove all the CO2 from the present day atmosphere (e.g., see Table 1 of Zhong and Haigh, 2013, Weather, https://doi.org/10.1002/wea.2072, pdf).
Looking at water vapour in the same way exposes some of the limits of the model they’ve set up for this tutorial, which was presumably kept simple just to teach some concepts to their students.  To do the same thing for water vapour as was done for CO2 would require removing 208 W/m2 of greenhouse effect (again, see Table 1 of that article), more than the total greenhouse effect of 150 W/m2 in their model.  The discrepancy is because they have too much solar radiation in the surface energy budget, so the diagnosed greenhouse effect doesn’t have to do as much work to balance a 288 K surface temperature.
A more realistic model would exclude the 80 W/m2 of solar radiation absorbed by the atmosphere, leaving an absorbed solar flux at the surface of 160 W/m2.  The balance is then $390 = 160 + \Delta E$, so $\Delta E = 230$ W/m2 and the revised perturbation equation for CO2 is,
$$\Delta E = 214 + 0.044[CO2]$$
The difficulty with H20 is that, unlike CO2, the concentration of water vapour is highly variable in space and time, so the equivalent equation will depend a lot on what you chose as present-day H2O concentration.  A ball-park figure for mean H2O concentration is 4000 ppm, which leads to the equation,
$$\Delta E = 22 + 0.052[H2O]$$
I should emphasise that this model isn’t intended for any serious calculation.  It’s just a tool to get students used to quantifying parts of the Earth system and how they can trade off against each other.


Is VLF-EM scanning for fractures a valid way to find groundwater for a well? I posted this question on Engineering Stack Exchange as well. I'm not sure if here or there is the better place. There is no agriculture stack exchange (much as I wish there was) so I am posting there as well as here.
I need to choose where to drill an agricultural well. I am trying to get as much water as possible (at least 100 gpm).
I am considering hiring a guy who claims to be able to find water using a device called an ABEM WADI. My understanding is that this devices uses VLF signals from far away transmitters to identify fractures in the ground. He says he walks in a straight line in a candidate area for well drilling, and looks for fractures noted on the screen of the WADI. He claims that areas with a certain type of fracture (I think he said 45° fractures were the best) are more likely to yield a lot of water.
To what extent is this method scientifically valid? It sounds legit, but methods of "dousing" or "witching" for water are often little more than divination, so I'm skeptical. I googled around and found some scientific papers about VLF-EM scanning, but I lack the science/engineering chops to interpret them.

VLF-EM is a perfectly valid technique for helping an expert decide where best to locate wells in geological environments where water is largely flowing in fractures. Typically it is a useful technique in fractured bedrock where a successful water well needs to intercept connected fractures or fissures. In other geologies, for instance porous sandstones, it would be much less useful. Drilling for water in fractured terrains is always a slightly risky proposition; geophysical techniques help site wells to intercept fractures but they can't guarantee yields, which will depend on how large the fractures are and how interconnected they are. A reputable contractor should be prepared to provide references from satisfied clients and that is a good starting point.


Lanes of flat ocean surface in coastal waters When the ocean is still, i.e. there aren't waves that disturb the surface, you often see "lanes" of water that seem flat as opposed to areas where the wind causes ripples. What causes this?

There can be many reasons for the lines that you see where the water is not rippled.

1) There is no wind on those specific areas.  Not likely in the photo used as the example but especially when there are cold fronts involved the wind can be very inconsistent over short horizontal distances.

2) You may be seeing the influence of boat wakes that passed over the area recently.

3) You may be seeing variation of the underlying ocean currents.  Especially near the coast with tide changes there can be zones of significant ocean current.  Wind and ocean currents have an influence on wave height and shape.  When the wind blows against the current you get higher steeper waves.  When you get wind blowing with the current you get shorter shallower waves (the smooth sections).  The currents are not just horizontal but have vertical components as well.  The lines identified could be vertical eddies in the current smoothing the surface whereas the smooth / rough line in the foreground is were the major ocean flow is going in opposite directions to each other.

4) If the coast in the foreground is shallow and there are waves coming to shore there then the lines identified to be rip currents caused by water returning from the coast line.

From my personal experience I would say that you are seeing variations in the surface ocean currents, and these currents change how the wind develops waves on the surface.

https://en.wikipedia.org/wiki/Wind_wave


What is the name for the forested areas in mountains below the treeline? Taiga is the Russian word for big areas of forest wilderness in high latitude regions. What about forests in the mountains? What is the name for the forested areas in mountains which are below the treeline?

For instance, see the image below:

Forests directly below the alpine tree line are high-elevation or Montane forests.  See more about Montane ecology here.

  Image from http://www.nature.com/scitable/knowledge/library/global-treeline-position-15897370


Are coral cays and coral atolls just volcanic islands? Are coral cays and coral atolls just a different type of volcanic island? When I hear: "volcanic island" I think at places like Moorea or Hawaii, but ultimately, coral cays and coral atolls lay their foundation on the residuals of a volcano, right?

No, they are not necessarily volcanic.

Both of these terms, along with many others like fringing reef and barrier reef, are just morphologic — to do with shape. They tend not to imply anything genetic — to do with origin. (The separation of description and interpretation is an important principle in observational sciences like geoscience.)

Cay   A low island, often of sand or coral. See Wiktionary.
Atoll   A ring-shaped coral reef. See Oxford English Dictionary.

The name Cay is sometimes applied more generally to an island or group of islands. In some cases, as in Cay Sal Bank, Bahamas, the feature is actually an atoll: a ring-shaped reef. Cay Sal Bank is one of the largest atolls in the world, and did not form on a volcano.

Charles Darwin hypothesized in his monograph The structure and distribution of coral reefs that atolls form when a fringing reef around a volcanic islands grows as the volcano subsides:

Indeed, Darwin turned out to be correct that atolls often have a volcanic origin, but Cay Sal Bank is a counter-example. I think it's fair to say that most people would assume that origin though, and lots of Internet definitions , so it's notable if an atoll formed some other way, e.g. on a non-volcanic seamount (see Keating et al., 1987, in Seamounts, Islands, and Atolls, AGU), or by island subsidence due to dissolution.


How long does it take for a stone to alter? We see stones and they appear to be the same throughout our life time. Mountains also appear to not significantly change. So do mountains and stones decompose? What is the life span of a stone? After it alters, what does it turn into?

Mountains and rock do decompose or weather into sediment.  A basic rock cycle overview shows the possible pathways between all three rock types (igneous, metamorphic, and  sedimentary) how one type can be transformed into another. After a rock is weathered into sediment, that sediment can become a rock again.

Weathering rates of rock vary widely regional based on the following factors:

Mineral composition of the rock  (some minerals are less stable at surface conditions than others)
Amount of plant life growing on the rocks and mountains. (Plant roots can be powerful chemical and physical weathering agent)
Amount of precipitation (Chemical dissolution due to rainfall is a significant weathering factor for some rock types (carbonate rocks)
Seasonal freezing periods.  (Ice expansion in cracks and fractures can weaken rocks over very short periods of time.
Temperature range of the region.  (I believe diurnal temperature differentials specially in high mountain deserts has a specific weather impact on some rock types).
Local earthquakes and volcanic activity.
Erosion due to water (streams, rivers, lakes, and oceans).
Erosion due to glaciers and ice flows.

You can get an estimate of weathering rates of different rock types for a local region by careful examination of cemetery gravestones.


How can I implement a visualization of archived convective data from numerical weather models? I've always found geographic visualizations of surface/mixed-layer CAPE models and other weather data to be incredibly interesting.

Here's a map featured by the Capital Weather Gang over at the Washington Post, during the June 12-13, 2013 derecho series in the Ohio Valley/Chesapeake Bay regions. It was created by WeatherBELL, which is a subscription service offering visualizations based on their proprietary technology.

Here's another map featured on the blog of Cliff Mass, a professor of atmospheric sciences at the University of Washington. This is an internal UW WRF model that is GFS-initialized.

I would like to know how I can take archived GFS or WRF data and visualize it on a map. Or even if that's possible (perhaps archived numerical data is only available to paid subscribers). What I would like to do is plot surface and upper-air readings to better understand the mesoscale setups for thunderstorms in the Pacific Northwest, where I live.

The best model archive I know of offhand is Iowa State Meteorology's Gempak model data in their MTArchive.  Looks like model-wise, they have at least 10 years of GFS (and the predecessor, the AVN).  No idea if the models are complete files (include CAPE) or not, though.

Gempak software is free, though you won't get graphics nearly as polished as WxBell; they've spent a lot of time fine tuning their setup, and likely use newer more flexible tools (probably GrADS or OpenGrADS, both also free).  You could probably get GrADS to use the .gem files, perhaps by converting them?


How are barometric pressure measurements traceable over centuries to 100 parts per million accuracy? The BBC News item Barometric pressure in London 'highest in 300 years' at least begins with

Overnight, Sunday into Monday, London's Heathrow Airport recorded a barometric pressure of 1,049.6 millibars (mbar).
It's very likely the highest pressure ever recorded in London, with records dating back to 1692.

It links to this Met Office tweet

So far Mumbles Head in Wales appears to have recorded the highest pressure during this current settled spell, with 1050.5 hPa earlier this evening. This remains a little short of the 1050.9 hPa recorded at Benbecula 16.1.1957, and the UK record of 1053.6 hPa, Aberdeen 31.1.1902

and then continues:

Met Office hourly observation reports recorded 1050.3 mbar at Liscombe in Devon, at 2100 GMT on Sunday evening. 1,050.2 mbar was recorded at Dunkeswell in Devon, and 1,050.5 mbar at Mumbles, in South Wales, shortly after.
None of these measurements breach the 1,053.6 mbar recorded at Aberdeen Observatory at 2200 GMT on 31 January 1902, which remains the national record, but the events of the past 24 hours certainly marked the first time for over 60 years that 1,050 mbar has been attained anywhere in the British Isles, said Mr Burt.

To discuss these records it is necessary to compare barometric pressure measurements to 0.1 mbar accuracy out of 1000 mbar, which is at the 100 parts-per-million level.
Question: How are barometric pressure measurements traceable over centuries to 100 parts per million accuracy? What was the procedure used to calibrate barometric pressure centuries ago that could be reproduced and compared to today's standards, or is there a very old standard absolute barometer somewhere that is believed to have remained calibrated?

Mark's answer about mercury barometers is correct - but it is not the complete story.

Barometers were initially constructed using water, not mercury, on the manometer principle.  Water is lighter than mercury, so a water barometer requires a 10.3m tube.  1mbar is therefore roughly 1cm, and 0.1mbar measurement is clearly trivial using a ruler with 1mm gradations.  Of course the exact units of measurement would depend on the country in which the measurements were taken, but it should be clear that measurement to this precision was perfectly possible, albeit with an inconveniently-large barometer!

Mercury barometers, with around 75cm height of mercury at 1bar, were significantly more convenient.  As Mark says, this does require a much more accurate ruler to measure it though.

But the accuracy of a simple ruler is not the complete story either.  The Vernier scale was invented (or at least popularised) around the same time.  With a floating Vernier marker, mercury barometers could be read accurately to around 1/10th of the ruler scale.  For a ruler marked in 1mm intervals, a 75cm column of mercury could therefore be read to 133ppm accuracy, which is close enough in accuracy to the original water-based barometers.


Is 2015's record average temperature evidence that we are now experiencing runaway climate change? 2015 had the highest global temperatures on record, as discussed in this question, beating the last record ... in 2014.

Are we now in a runaway climate change regime, where zero further human impact on the environment will not prevent change to the equilibrium state of the Earth's atmosphere?

Runaway climate change is, given our current state of knowledge, only something that could be confirmed in historic context - in the rear-view mirror. Inconveniently, there's likely to be a much-diminished version of human civilisation around to observe it, if and when it does happen.

In other words, it's too early to tell if we've passed a catastrophic tipping point.

We don't know what the equilibrium state of the Earth's atmosphere is. It will take 30 years for our current stock of GHG emissions to fully show its effects: and we'll be continuing to release GHGs for a while, so the equilibrium will continue to change.

But it's worth bearing in mind what we can do, when we really have to; World War II saw massive realignments both in industrial production and in expectations within a very short space of time: after decades of delay, it now seems likely that decarbonisation will require at least a similarly fast and large industrial realignment; and it is possible.


Water veins underground causing health problems It seems to be given that around my country everybody believes in water veins (that's the best that Google Translate could come up with. Basically underground water currents) that somehow affect humans. For example, one of the beliefs is that if you put your bed over one of these water veins and sleep on it, you'll start getting heart problems within in a couple of years.

Since I'm slightly more skeptic, I tried googling around, but all I found was some weird new age websites. So I'm asking the specialists. Is this underground water veins health effect thing real?

In my opinion, there is no such thing as water veins as described in this article, but, it is a fact that there is water circulation underground.

In the natural environment, water can either circulate in porous mediums (like within the small spaces between sand grains in sandy soils) or as underground streams. There is also the concept of the water table and aquifer recharge and depletion.

This schematic provides a broad picture on the importance of groundwater

More info here as well.

Some regions composed of rocks, especially carbonates (karst) can have more often channelized underground streams, as the ground is not necessarily porous so water is kind of forced to flow where there is an opening (see following figure). (More info on karstic landscape here)

So that was a small overview on how water can circulate underground.

Then people getting sick from water circulating underground is not because of the veins per se, it could be because of moisture (or many other factors). But then living near a lake or any streams, any wet areas or in a badly insulated house could make people sick as well.

This is 'old wives' tale' (no offense - English is not my primary language I am not sure how to say) and is not really a thing as presented in the http://swissharmony.com/en/water-veins-neutralized site. There has been no new research in a medical paper about geopathy since 1940 (wonder why?). You are doing well in being skeptical! To conclude I am sure many people living in drylands would be more than happy to be  'sick' over a vein.


Would hurricanes on an ocean planet continue indefinitely? Hurricanes seem to run out of steam when they make landfall.
If our planet were entirely covered by ocean, would hurricanes continue indefinitely?  Would they keep gathering energy and increasing in intensity until...?

No. As it is, many hurricanes never make landfall. In an oceanic world I could see three fates happening:

Hurricanes that dissipate due to dynamical features or climatological features.
By dynamical features, I mean things like two hurricanes that shear each other out or produce an environment that can't be sustained. An example of the latter is upwelling, which generates cooler water that saps the energy from the hurricane. A climatological feature that might prevent a hurricane from developing indefinitely might be the Azores high. As it is, there are places that hurricanes don't seem to go.

Hurricanes that undergo extratropical transition.
Notice in the figure above, the hurricanes just disappear near the poles? As they come closer to the poles, the temperature difference becomes larger. Eventually they no longer look like tropical cyclones/hurricanes (little to no temperature difference), but rather look like an extratropical cyclone (see this link for some differences). This process is called Extratropical transition.

Chavas and Reed (2019)
While looking up papers for this question, I stumbled upon this paper. It implies that we would get longer lived hurricanes spreading the entire planet. I'd be a little skeptical of this result though, since it ignores the fact that the earth is heated unevenly, which drives most of the climate.

On a side note, such simulations do exist. These are called Aquaplanet simulations. Some studies I found include:

Li et al. (2011)
Merlis and Held (2019)
Chavas and Reed (2019)
Viale and Merlis (2017)

And for kicks and giggles, if you want to consider what the worst-case scenario for a hurricane could be, such a thing has been named a "Hypercane" (see here, too).


How are organic walled microfossils preserved in the fossil record? Organic walled microfossils have no hard mineralised parts, how are they preserved in the fossil record?

Organic-walled microfossils (wether they be dinoflagellates, pollens, spores or "acritarchs")  all have in common to contain an organic compound known as sporopollenin (for the spores and pollens) or dinosporin (for dinoflagellates and, I believe, acritarchs as well). Both compounds have chemical and structural similarities but have appeared independently.

Those compound are incredibly resistant. To give you an idea, to collect siliceous microfossils we first dissolve the sediments with HCl (hydrochloric acid) to get rid of carbonate microfossils. Palynologists (who study such organic-walled microfossils) uses HF (hydrofluoric acid) to get rid of both carbonate and siliceous microfossils (e.g. Doher 1980). Sporopollenin therefore resist to HF, which has a pH of ca. 3. In addition to this, they are also unusually resistant to microbiological degradation (e. g. Gunnison & Alexander 1975).

They are however not resistant to oxydation, hence, probably, why we don't find more of them in the sediments. Additionally, to break sporopollenin walls (in order to study the inner side of those walls) ultrasound can be used (e. g. Lennie 1968).

"Organic-walled" doesn't mean no hard part, it just means no "mineral" hard part.

Sources:
Doher, I., 1980. Palynomorph preparation procedures currently used in the paleontology and stratigraphy laboratories, U.S. Geological Survey. Geological Survey circular, 830: 1-29.
Gunnison, D., Alexander, M., 1975. Basis for the resistance of several algae to microbial decomposition. Applied Microbiology, 29: 729-738.
Lennie, C. R., 1968. Palynological Techniques used in New Zealand. New Zealand Journal of Geology and Geophysics, 11: 1211-1221.

At the request of the OP, a little word on another group of organic-walled microfossil with a extensive, coherent Paleozoic fossil record: the Chitinozoans.

This enigmatic group was found by Eisenack (1931) and because of their resistance to acids & bases he thought they consisted of chitin, hence the name he gave them. However studies (Voss-Foucart & Jeuniaux 1972; Jacob et al. 2007) showed that they do not consist of chitin or any kind of chitin-like bioproduct but of a network of kerogen with aromatic compounds. The diagenetic path that lead to this chemical composition is however unknown, meaning that we know neither what was their chemical composition when those organisms (NB: we don't know as well what their biological affinities are, though metazoan eggs seem to be a popular hypothesis, see e.g. Paris & Nõlvak 1999) were alive nor how they preserved.

Additional sources:
Eisenack, A., 1931. Neue Mikrofossilien des baltischen Silurs I.
Palaeontologische Zeitschrift, 13: 74–118.
Jacob, J., et al., 2007. New insights into the chemical composition of chitinozoans. Organic Geochemistry, 36(10): 1782–1788.
Paris, F. & Nõlvak, J., 1999. Biological interpretation and paleobiodiversity of a cryptic fossil group: The “chitinozoan animal”. Geobios, 32(2): 315-324.
Voss-Foucart, M.F. & Jeuniaux, C., 1972. Lack of chitin in a sample of Ordovician chitinozoa. Journal of Paleontology, 46: 769–770.


Could Global Climate Change increase the average moisture in the air? Given several hundred years, assuming global climate change results in the melting of the polar ice caps which leads to an increase in surface area of the oceans and an overall warming of the earth (although I'm not quite certain to what extent the earth as a whole could increase in temperature in several hundred years), would the result be an increased amount of evaporated water into the air increasing the overall humidity?

Out of the total water on Earth, only a tiny fraction is held in the atmosphere at any given time.  Therefore, the direct effect of melting land or sea ice will not result in an increase in specific humidity.

However, warm air can contain more water than cold air, according to the Clausius-Clapeyron equation.  Therefore, the climate warming that causes the ice caps to melt, will also result in an increase in average specific humidity.  This is (approximately) an exponential relation (I don't have access to my textbooks right now, but googling saturation vapour pressure water equation yields many forms; I do not include them here because none I found use SI units).

Saturation vapour pressure of water.  Source: Chemguide.

See also the (not very good) Wikipedia article on Vapour pressure of water.


Explanation for single rainbow that contained colors several times I saw a rainbow outside Silverton, CO last week that for a few minutes seemed to show part of the color cycle (red to purple) several times within the same band. This picture is how it looked to my eye. I assume this is some refraction phenomenon of multiple rainbows, or ... ? It was also a double, but that part isn't shown.

I took another picture a few minutes later of it looking normal (the rainbow brightened, the droplets were bigger, and there was a strong double):

What is causing this strange banding?

It a supernumerary bow, which results when the droplets that create the rainbow are very small and of nearly uniform size. The droplets need to be small enough so as to make diffraction a significant effect.


Regarding compression, shuffle filter of netcdf4 I read the doc but still have no idea about

what are the advantages to enable or disable the shuffle,
what level [0-9] of compression is optimal,
what's the best choice of chunk size?

I made some pictures on my tablet to explain everything a bit better. Sorry that they are not that nice.

Shuffle

If we do not us shuffle, we store on value (float, double, integer, short integer, ...) after another. Thus, each variable itself is stored contiguously in memory. The first bit of a second value follows the last bit of the first value. If we use shuffle, the first bit of all variables is stored contiguously in space, followed by the second bit, and so on.

The figure above shows an array of six 8-bit integers (only 8-bit because it was less painting work ;-) ). The vertical black boxes split in 8 compartments represents on 8-bit integer. The orange arrows from left to right indicate how the bits would be stored with shuffling.

Now we assume some example values: We have an array with the values 4, 2, 4, 5, 7, and 6. It is shown in the figure below. The first row shows the decimal representation. The matrix below is the binary representation. Each binary column represents the corresponding decimal number in the first row. The red arrows indicates the normal storage order. The orange arrows indicate the shuffled storage order.

Now we can write down the order of bits in the memory. I wanted to use color. Therefore, you get another picture:

We have a lot of zeros in the beginning of the binary representation of each value (because we have very low values). The shuffling is favorable in this situation because we have a long contiguous memory part filled with the same number/condition (= 0).

If we had no low numbers but higher numbers, (but) which are close to each other, we would not have a long contiguous memory part filled with 0s (zeros) but it might be six 1s and then six 0s. Commonly in netCDF files we have much larger arrays. Lets say a 4-dim array with 100 x 200 x 30 x 365 values, which are quite similar to each other. Then we would have often 2.19 x 109 contiguous 1s or 0s in memory, which is quite nice for compression.

However, if neighboring values differ considerably, shuffling might not be a good idea.

Chunking

If we have an uncompressed file (= no chunking; or one big chunk), a n-dim array is stored contiguously in memory: at first all values of the first row (first index) of the array are stored contiguously in memory; then we go to the next row (increment second index by one) and write the second row contiguously into the memory; and so on.

We might also start with the last index and do it the other way around ... - depending on the programming language and on the definition of what are rows and columns. But the principle is the same.

The figure below shows an example for a 2-dim variable with one spatial and one temporal dimension. The red arrows indicate how the data is aligned in memory. The black dots are individual values in our 2-dim array.

Now, we want to extract a time slice (all spatial values at one time step) and a space slice (all temporal values at one location) from our data. In the second case we get a time series (could be a time series of model data). In the first case we get a picture of the current situation (could be for a map). The blue and green markings in the figure below indicate the time and space slices.

The difference between time and space slice is the following. The time slice is fast to extract because the values are stored contiguously in memory. The space slices takes more time because only each sixth value is extracted. Is this example the extra work/time spend is low. However, if we have a large 4-dim variable, the time-slice-extraction will be faster than the space-slice-extraction.

When we compress data, we can chunk it. That means, that we split our large array-variable in sub-arrays. For the user it looks the same from the outside. netCDF-4 does chunking automatically, when we compress data but don't define a chunking pattern.

The figure below shows an example, in which our data was split into three chunks. The red arrows indicate the alignment of our values in the memory. This is just an exemplary alignment.

Now, we extract time and space slices again (figure below). Green and blue indicate the slices, again. Here we see that the space-slice will be much easier/faster to extract then before. However, the extraction of the time slice will take more time.

In addition, the compression will differ when you change the chunk sizes. The background is similar as described in the Shuffle section: depending on which values are neighboring each other, the one or the other chunking might be favorable.

Now to your question: what's the best choice of chunk size?

focus on usage

It depends on your data usage and you access pattern. If you often extract time series at specific locations, it might be favorable to define the chunks in a way that the values corresponding to one location are close to each other aligned in memory.

But be careful, some software like cdo access the netCDF data always in the same way - independent of what you do with it during the processing. Thus, if you don't access the file directly via the C- or Fortran-netCDF4 routines but via some other software, the best chunking pattern might not depend on what you want to do but how the software does it ... . Some software might - for example - always read data along the spatial dimensions first, although you want data along the time dimension.

focus on compression:

The size of the compressed file varies with the chunking layout. The situation is similar as described in the Shuffle section. If the data are more effective to compress in time dimension, the chunking in my example figure above might be favorable for file size (e.g. high variability in space but low variability in time).

Chunking summary

The best choice of the chunk size depends on your access pattern, on the software you use, on your data itself, and on your focus on access time vs. storage space.

Compression level

The choice of the compression level depends on your aim. If you just want to store the data (in an archive or where-ever) and have it as small as possible, you might use compression level 9.

If you want to access data often and fast, you should choose a lower compression level. We use compression levels up to 4. Above that the reduction in file size is very low (for us) so that we do not have a reason to go beyond.

Example: Currently, I work with an ocean model. We have a lot of land in our model domain (roughly 1/3). Compression of level 1 is sufficient to reduce the file size by approximately 95%. However, this is a special case.

summary:

I tried to give an overview of the features you asked for. The exact choice depends on you particular use case and cannot be generalized. For you, my answer might be too late but I hope that it might help some others. For me, the document you linked helped a lot in the past.


How can a non-geologist identify a rock? I found a rock on a beach in north-east Evia, Greece. Half is light gray, and half is dark gray. There are white (or very light gray) thin lines that form swirls throughout, crossing the light/dark gray boundary in the main body of the rock. To me, they look like fossilized leaves or something similar.

What is the best way to work out what this is? There seems to be an abundance of different rock types, many colors, but there are many similar stones to this one, all worn into smooth rounded pebbles.

OK, so you've found yourself an interesting rock and you want to know how to identify it. I am going to go ahead and assume that you haven't studied Geology before (apologies if that's an assumption too far).

The first thing you can do is to head to your local public library and find a basic "rocks, minerals and fossils" identification book, and try to match up what you have with something in the book. Most of these books will include some kind of description of the various tests you can do (Mohs Hardness Tests, Acid Tests, Flame tests etc).

A quick google search for the geology of the area in which you found the rock might also give you a good starting point. You are more than likely not going to find an exact match by doing this, but it will help later if you have some idea of what you might have. It also means that you will have to look at the rock critically and you'll gain far more for having tried to identify it yourself. (I work with helping ID fossils on a regular basis, and it's far more rewarding if the person who has found the fossil has some idea as to what they have, or at least a reason for their identification).

If that doesn't get you anywhere, you can turn to the internet, there are places such as the NHM's Nature Plus where you'll find other people including experts and amateur rock hounds who might be able to give you more help. You will want to have good photographs with a scale (coins, Lens Cap, Rulers all apply).

If all else fails, Head to your local museum with a geological collection and look at the collection. You can also ask to speak to a geological curator and they should be able to help you identify your specimen (as your profile lists London as your location, the Natural History Museum's Angela Marmot Centre, The Horniman Museum, or British Geological Survey are all good bets).


What processes produced the basalt columns of the Giant's Causeway? The Giant's Causeway is, according to the Wikipedia page was formed during

  during the Paleogene Period, Antrim was subject to intense volcanic activity, when highly fluid molten basalt intruded through chalk beds to form an extensive lava plateau.

Of particular note is the distinct columnar pattern (as seen in the picture below):

Formed, according to the Wikipedia page by

  As the lava cooled, contraction occurred. Horizontal contraction fractured in a similar way to drying mud, with the cracks propagating down as the mass cooled, leaving pillarlike structures

What was the geochemical/petrology process(es) cause the contraction features that resulted in the columns being formed in the Giant's Causeway?

These are basalts with columnar joints. Basalt is an igneous rock that forms when magma (liquid + crystals) erupts onto the surface as a lava flow or gets injected into cooler shallow crust and forms an intrusive dike or sill.  Because basalt cools quickly, basalt commonly contains glass as well as crystals. The physical properties of magma changes rapidly as it cools through the liquid-glass transition temperature. When a magma cools through the liquid-glass transition temperature, its specific volume decreases and its viscosity increases rapidly. The volume of the lava flow decreases (it shrinks) and it become more viscous and brittle. This creates stresses in the lava flow that eventually causes it to fracture. Columnar joints are fractures that have formed because the stress has exceeded the brittle strength of the rock.


How to understand Mohr diagram? Structural geologists use Mohr diagram to evaluate stress on rock's surface, but I find it difficult to understand how this diagram works (Though I am good at math). Where can I find a good explanation of Mohr diagram?

Here is an excellent explanation of the math as related the stresses represented by the Moh'r circle.

http://www.geology.sdsu.edu/visualstructure/vss/htm_hlp/mor_cir.htm


How often does the moon "set" for us compared to the sun? I am working on a game, and I have a day/night cycle. Currently I have the sun. Currently every "sun day" is 24 hours, with that being said, how long is every "moon day"? In other words, how much does the moon lag behind the sun. I just need to figure out what the moons speed should be in relativity to the sun. I've done some searches, but wasn't quite sure how to properly word this question.

As noted in comments, the earth rotates on its axis in about 23hrs 56 minutes. This is known as the sidereal day, that is, the day with respect to background stars. (that's not quite true, but it's good enough unless you're dealing with periods of thousands of years with high accuracy - see the linked wiki article if you care about the detail).

At the same time, the Earth is also orbiting around the Sun in the same direction, and the combination of the Earth's spin and its orbit around the Sun gives us the 24-hour solar day that we are familiar with, and that you have already modelled in your game.

Now consider how the Moon rises and sets, when seen from a position on Earth. The primary cause of this is, again, the Earth's rotation with it's just-less-than-24-hours period. In addition, this time, one must consider the motion of the Moon around the Earth, which is again in the same direction as the Earth's spin. This results in a period of about 24 hr 50 mins for the apparent motion of the Moon across the sky (Source). For your game that may be sufficient info, although if you want to be accurate it is complicated.

Remember to also take account of the phases of the moon - because the whole earth-moon system is also in orbit around the sun, and because the moon is only visible via reflected light, the mere fact that the moon is above the horizon when seen from a given point on earth does not mean that it is visible.


Are the magnetic elements of meteorites that have struck Earth aligned with the magnetic field? I was just pondering this question; do meteorites containing significant magnetic metal elements displace paleomagnetism the same way that magnetic striping on the ocean floor occurs? When the meteorites pass through the atmosphere do they actually get hot enough to go beyond the curie point of any metal-bearing minerals that are within and then subsequently align with the magnetic field as they cool back down?

If so; I assume that would that be indicative of the Earth having an inner liquid core producing a magnetic field or could something else be the contributing factor to the alignment?

The surface of 'iron' meteorites certainly gets hot enough to exceed the curie temperature, hence the characteristic ablation texture that you see on meteorites in museums. However, that's a surface feature, and wouldn't affect the interior of all but the smallest of meteorites. The tumbling passage through the atmosphere for just a few seconds, coupled with the shock of impact when it landed is such that there wouldn't be any clear magnetic signature of anything within the outer skin of the meteorite.

In large meteorites, consisting of solid Ni-Fe, the residual magnetism seems to reflect the magnetic field of that part of the solar system from whence they came. Other meteorites contain fragmentary components of varying magnetic orientation, also, (presumably) related to magnetic fields within the early history of the solar system.


What is the difference between a flood and a mudslide? Description

Floods and mudslides are both occurrences, which can be very destructive.

Question

(Hopefully after the edit the question is more clear)

  What is the difference between a flood and a mudslide?

A flood occurs when land that is normally dry is covered by water. The source of the flood water is generally from bodies of water, such as: rivers, lakes, dams and even the ocean.

Rivers can flood, when:

  the flow rate exceeds the capacity of the river channel

Similarly, excess water run-off during heavy rain can cause floods when the water cannot drain away quickly enough.

Flooding is the act of flood water accumulating in a area that is being flooded.

To understand mudslides you need to know what a landslide is.

A landslide is when a quantity of rock slides down a slope.

A mudslide is similar to a landslide. The only difference being the type of material that is moving. With landslides, the material moving is generally composed of rock and maybe some soil. In mudslides, the material being moved is loose, finer grained material such as mud and clay.


What is Celsius degrees to tenths? I'm looking at a historical weather data report and the TMAX and TMIN are like this: 44 and -21, the following day 72 and 17. First I thought it was Fahrenheit, but the conversion didn't make any sense because it would be +6°C one day and +22°C the following day in January in NY, NY.

  Then the note said  - * Values denoted with “*” (i.e. temperature
  values) are in Celsius degrees to tenths on csv.

Does it mean 44 is actually 4.4 and 72 is 7.2? That would make much more sense.

More examples TMAX/TMIN:

  44/-21, 72/17, 83/-10, 128/61, 106/-49, -49/-71

PS. I know there is a possible duplicate that MAY have an answer to my question, unfortunately it doesn't. Some comments (not the answer itself or the question) explain WHY it is the case in vague and guessing terms, but it doesn't give an answer to WHAT it is, which is my question. Nobody can say for sure if 44 is 4.4 and -21 is -2.1 and I can't rely on guesses.

Your question is similar to this one: Deciphering NCDC data

In the comments for that question I posted the following two comments which will most likely answer your questions:

  regarding the usage of tenths of a degree, it may be a continuation of an ancient data format from the early era of computers. Removing decimal points changes numbers to integers. In old computers memory capacity & calculating speed was an issue. In binary digits, integers are half the size of floating point numbers & a quarter the size of double precision numbers. Hence the use of integers speeds up calculations & requires less memory (disk drives, tape & RAM) than floating point numbers. In the old days, tape was used heavily as an external storage medium

  There is logic in maintaining the old data format for consistency. If the data format was changed then all the old data would need to be changed & checked to ensure there were no errors. If the format was changed as of a certain date but the old data remained in the old format, people would need to be mindful of the change & when it occurred. Analysis apps would need to first check if the data was from before or after the date of change, condition the data accordingly before doing the calculations. It's easier to keep the old format


How would pesticide vapor drift behave near a valley? I am considering buying a house in a valley with pesticide-intensive agriculture on both sides. Schematically, it looks like this:

It won't win any design awards, but it should make things clear.

My question is how the pesticide vapor drift would behave? Wouldn't there be a high risk that the cold air with the vapor gets trapped there?

While @Gordon Stanger gave an overall perspective about pesticides in general in his answer you can deduce some key points about the micrometeorological conditions of the area.

Assuming pesticides as relatively large aerosol particles/droplets spayed quite close to ground they are mainly dry deposited to surfaces. If your house is as close to the pesticide spaying areas as your schematic implies, you might have a problem (assuming pesticides are dangerous to you, more in @Gordon Stangers answer) only if during the spraying air gets trapped into the valley.

Assuming the spraying is only done in daytime and summertime the chances of an inversion in the valley are smaller and they would only stabilize the air preventing mixing with your valley air and pesticide air.

Strong winds (if the location is near a coast (probable sea breeze) or it's otherwise known to be windy) might carry some pesticides to your direction, but overall adding vertical mixing dramatically lowering the average concentrations.

Your most worst case scenario is if calm (not windy) very sunny days are very often. Sun will in different times of days heat at least either of the slopes of the valley causing air to rise on that side. Replacing air is sucked from the other side creating a steady flow from pesticide rich agricultural areas to your valley. Pesticide being assumed a large aerosol will deposit most likely in the valley (if not in the bottom then in the drafts uphill).

Also rainy weather is good for you as the pesticides will most likely wet deposit near their source.


Is there any link between sea-water inflitration into groundwater and nitrate? I recently read a pop-science article about sea-water infilitration into (sweet) groundwater. One specific instance mentioned was the gaza strip: Exzessive well building and drawing of groundwater lowers the groundwater level, this leads to sea water infiltration. Then the article states the the nitrate content in the groundwater is higher, leading to blue baby sysndrome.

Now, I assume that an elevated nitrate content in the groundwater is due to fertilizer runoff, damaged sewer systems or similiar and unrelated to the saltwater problem, the author of the article simply mixed those problems up. But I'm not sure, hence this question: Is there any causal link between sea-water inflitration and groundwater nitrate?

An answer not specific to Gaza would be ok as I want to understand possible mechanisms.

While the context and specifics would likely vary from site to site, the situation along the Gaza strip may be due to contamination of the Mediterranean Sea.  I am unsure of natural levels of Nitrate in ocean water, but I know that it is possible to contaminate water, independent of it's salinity.

Nitrate, like other water-soluble ions, ultimately is transported from the land to the oceans via the hydrologic cycle.  Waste from marine organisms also likely contributes nitrate.  This paper talks on the content of nitrate in ocean water. For more information on the various major constituents of sea water, check out this site.

There has been reported incidence of sewage draining into the Mediterranean, which would explain nitrate contamination in conjunction with sea-water intrusion.


Where can I obtain ocean wave data of the Southeast Asian region? I am interested in obtaining ocean wave data (preferably from actual measurements), such as wave height, period, and direction, in the Southeast Asian region. Where can I obtain them?

The only open and ongoing data source for in-situ ocean wave measurements I am aware of is the National Data Buoy Center. Though NDBC manages data service from plenty of moored buoys in the Gulf of Mexico and the Atlantic and Pacific coasts of North America, unfortunately there isn't much in your region of interest.

The only buoys I have found that are somewhat near the Southeast Asian region are 2 buoys on the east and west side of Guam, and one right by Northern Mariana Islands:

http://www.ndbc.noaa.gov/station_page.php?station=52200
http://www.ndbc.noaa.gov/station_page.php?station=52202
http://www.ndbc.noaa.gov/station_page.php?station=52211

These buoys provide directional energy spectrum data, as well as integrated quantities like significant wave height and mean and dominant wave period. I've written a Python library that lets you parse NDBC server and access data from buoys from command line or your Python programs. Once I tidy it up and make it public, I will update this answer so that other people can use it.

Your other option, as suggested by @DeerHunter, is to use altimetry data from polar-orbiting satellites. Although these are sparse and provide only wave heights (no period or direction information), they may be your only bet depending on the region of interest.


Which ocean is going to be swallowed by the Supercontinent Cycle, Atlantic or Pacific? The register shows several supercontinents have been formed on Earth's History:

  "The most recent supercontinent, Pangaea, formed about 300 million
  years ago (0.3 Ga). There are two different views on the history of
  earlier supercontinents. The first proposes a series of
  supercontinents: Vaalbara (c. 3.6 to c. 2.8 billion years ago); Ur (c.
  3 billion years ago); Kenorland (c. 2.7 to 2.1 billion years ago);
  Columbia (c. 1.8 to 1.5 billion years ago); Rodinia (c. 1.25 billion
  to 750 million years ago); and Pannotia (c. 600 million years ago),
  whose dispersal produced the fragments that ultimately collided to
  form Pangaea".

  Source: Supercontinent Cycle, Wikipedia

I would expect then a new supercontinent to form in some million years, but this implies Atlantic or Pacific Ocean, both with ocean-ridges and divergent margins, to disappear.

Wich one will be closed and wich one will survive to Supercontinent Cycle?

The pacific has already lost part its spreading center, north america has been pushed over it.. A few tiny non-contiguous plates like the  Juan de fuca plate is all that is left of the east pacific plate. in places like the san-andreas the north american plates has complete overridden the spreading center.

In truth there are four possible predictions for the future: Novopangea, Pangea Ultima, Aurica and Amasia. two predict the atlantic disappearing one predicts the arctic and the final predicts the loss of the pacific. I think the latter two are more likely given what we see in the north america/pacific interaction but this is just opinion, the truth is we don't know a lot about how oceanic plates disappear or how spreading centers die because by their very nature they do not leave much evidence behind.


Esker vs. Kame vs. Drumlin - what's the difference? In researching glacial features, I came across the terms esker, drumlin, and kame. I know that they are all depositional features that are shaped like a mound. My impression is that an esker is longer than a drumlin, which is longer than a kame. What other differences distinguish between the three?

Eskers are glaciofluvial deposits from sediment carrying subglacial tunnels. As the water emerges from a tunnel at the bed of an ice sheet or glacier it will slow down. Since the sediment movement depends on water velocity the sediment will be deposited. The results is a highly localised deposition. When glaciers retreat the point of emergence for the water will of course change with the edge of the glacier. Hence the deposition will occur progressively further upstream leaving a narrow trail of sediment accumulation. Much more can be said but the result is ridges sometimes hundreds of kilometres long that extend pretty much perpendicular to the past glacier edge, the way the water flows from within to the edge of the glacier.

Kames are hummocky terrain formed by material that has been transported by glacier melt water. The reasons for the hummocks is that when the sediment was deposited, chunks of ice were buried by the sediments and when that ice melted a hummocky terrain was formed. A key here is that the deposition of sediments from sediment transport would not be able to form the irregular hummocky terrain as a primary feature, there has to be other processes involved. Kames are therefore usually an extensive land form that does not necessarily have a preferred extension. As with eskers the origin of the water and sediment is the same, the base of the glacier.

Finally, drumlins. These forms are elongated land forms, in the direction of ice flow, often some kilometres in length, width of a few hundred metres and a height of tens of metres. This varies a lot though. These forms are not formed by running water and sediment transport but formed beneath the ice. In the literature they have been described as both depositional and erosional land forms, although a depositional formation seems to be most common. They seem to consist of whatever material is present beneath the ice but because the most common sediment beneath glaciers is till this is also what most drumlins consist of.

So eskers and kames have som relationship in the origin of the sediment that make them up. Drumlins are of completely different processes. Much more could be said and all details are not completely understood when it comes to many glacial landforms and their formation.

ADDED:
The formation of drumlins, and hence also their characteristics is too complex to be explained in a short answer here. Three scientific papers that will help gaining a deeper understanding of drumlin formation are (I suggest googling on the titles to find copies):

Patterson, C.J., Hooke, R.L., 1995. Physical environment of drumlin formation. Journal of Glaciology 41 (137), 30–38.

Stokes, C.R., Spagnolo, M., Clark, C.D., 2011. The composition and internal structure of drumlins: complexity, commonality, and implications for a unifying theory of their formation. Earth-Science Reviews 107, 398–422.

Roger LeB. Hooke, Aaron Medford, 2013. Are drumlins a product of a thermo-mechanical instability? Quaternary Research. http://dx.doi.org/10.1016/j.yqres.2012.12.002


How to map emission inventory from lat&lon corrdinate to WRF model grid Here, I have a regional emission inventory, which mainly contains the varibales of lat,lon,emission,and the emissionshape is (lat,lon).

For example :

ODIAC, the  spatial resolution is 1*1 deg, and emission shape is (180,360)，units : gC/m2/d;
Hestia, the spatial resolution is 0.002*0.002 deg, and the emission shape is (521,560),units: Kg;

For now, I have to map the emission from the geographic coordinate (lat,lon) to WRF model grid, which may look like 99*99 with grid spacing of 3km,or 87*87 with  grid spacing of 1km.

It seems that the process of mapping involves the calculation of area of old grid of emission inventory.

I am confused about how to do. Is there any efficient method to deal with it?

Thanks for all the help.

I would suggest using cdo for your purpose. At least for variables, which values are independent of the grid cell size, one can use cdo.

cdo

cdo (Climate Data Operators) is a command line program to process netCDF and GRIB files. It is developed an maintained by Uwe Schulzweida and colleagues at the Max-Planck Institute for Meteorology in Hamburg, Germany.

cdo Homepage
cdo HTML Manual
cdo Forum

cdo provides different operators to process your data. You can chain several operators in one command. You always start with the call of cdo. Examples:

cdo OPERATOR1 -OPERATOR2 -OPERATOR3 inputfile1.nc inputfile2.nc outputfile.nc
cdo OPERATOR1 -OPERATOR2 inputfile1.nc -OPERATOR3 inputfile2.nc outputfile.nc

The first operator is just appended to cdo. All further appended operators need to have - as suffix.

example

Assume, we have two files (file1.nc and file2.nc) with some ocean data (sst, salinity, u, v, ...). We want to calculate the difference between the sst of both files. This is done via

cdo diff -selname,sst file1.nc -selname,sst file2.nc outfile.nc

We could do this also in four steps:

cdo selname,sst file1.nc sst_of_file1.nc
cdo selname,sst file2.nc sst_of_file2.nc
cdo diff sst_of_file1.nc sst_of_file2.nc outfile.nc

Interpolate data with cdo without considering grid cell size

cdo provides different operators for interpolation. REMAPBIL for bilinear interpolat, REMAPNN for nearest-neighbor interpolation, and so on. They are listed in the manual. I use remapbil here as an example.

cdo remapbil,NEW_GRID_DEF file_old_grid.nc file_new_grid.nc

The file_old_grid.nc is your input file and file_new_grid.nc is your output file. Here you find an example from my work at GitHub:

cdo remapbil example

The grid definition on your input file file_old_grid.nc needs to be recognized by cdo. To test, whether it is recognized you can try

cdo griddes file_old_grid.nc

If it prints out the correct grid definition, then everything is fine. If not, you need to correct the definition of your lon-lat grid. Please have a look in the respective section below for details.

The NEW_GRID_DEF is a file, in which the target grid is described. If your target grid is a nicely defined grid, you can write this file by hand. E.g. it could look like (copied from the HTML manual of cdo):

gridtype = lonlat
xsize    =   60
ysize    =   30
xfirst   = -177
xinc     =    6
yfirst   =  -87
yinc     =    6

Please look for "CDO grid" and "grid description" in the cdo HTML Manual to fine more examples and explanation on it.

If you don't have a nicely defined grid, you can generate your NEW_GRID_DEF. This is, what I have often done, because our chemistry transport model setup needed a non-nicely defined grid.

cdo griddes file_with_wrf_grid_definition.nc > NEW_GRID_DEF

In file_with_wrf_grid_definition.nc, the model grid has to be defined and it needs to be recognized by cdo. Here you find an example from my work at GitHub:

cdo make grid definition

How to make cdo recognize

cdo assumes that your file conforms with the CF Conventions (Climate and Forecast Conventions). Please have a look in the respective chapter of the CF Conventions Document to get a general description.

A working grid definition could look as follows (as ncdump output):

dimensions:
  time = UNLIMITED ; // (1 currently)
  lay = 1 ;
  lat = 78 ;
  lon = 62 ;
variables:
  float lat(lat, lon) ;
          lat:long_name = "latitudes       " ;
          lat:units = "degree north    " ;
          lat:var_desc = "latitude (south negative)                                                       " ;
          lat:cell_methods = "TSTEP, LAY: mean" ;
  float lon(lat, lon) ;
          lon:long_name = "longitudes      " ;
          lon:units = "degree east     " ;
          lon:var_desc = "longitude (west negative)                                                       " ;
          lon:cell_methods = "TSTEP, LAY: mean" ;
  float DATA_VAR(time, lay, lat, lon) ;
          DATA_VAR:long_name = "some long var name" ;
          DATA_VAR:units = "some unit" ;
          DATA_VAR:var_desc = "some description" ;
          DATA_VAR:coordinates = "lat lon" ;

The important aspect is that the data variable has an attribute coordinates, which value contains the two lon and lat dimensional variables (I attached a second example so that it becomes clear). Additionally, the standard_name and units attributes should be properly set at the dimensional variables.

dimensions:
  time = UNLIMITED ; // (1 currently)
  lay = 1 ;
  lat = 78 ;
  lon = 62 ;
variables:
  float lat_1(lat, lon) ;
          lat_1:long_name = "latitudes       " ;
          lat_1:standard_name = "latitudes       " ;
          lat_1:units = "degree north    " ;
          lat_1:var_desc = "latitude (south negative)                                                       " ;
  float lon_1(lat, lon) ;
          lon_1:long_name = "longitudes      " ;
          lon_1:standard_name = "longitudes      " ;
          lon_1:units = "degree east     " ;
          lon_1:var_desc = "longitude (west negative)                                                       " ;
  float DATA_VAR(time, lay, lat, lon) ;
          DATA_VAR:long_name = "some long var name" ;
          DATA_VAR:standard_name = "the standard name" ;
          DATA_VAR:units = "some unit" ;
          DATA_VAR:var_desc = "some description" ;
          DATA_VAR:coordinates = "lat_1 lon_1" ;

Interpolate data with cdo with considering grid cell size

No idea how it works with cdo


Are there any saltwater rivers on Earth? I'm curious if there are any saltwater rivers on Earth. These would presumably arise if a saltwater lake had a river outlet to the ocean.

However, all the saltwater lakes I looked at (Caspian Sea, Dead Sea, Great Salt Lake Utah), apparently don't have any river outlets.

Do any exist? And the obvious follow up, why or why not?

Edit: For the purposes of this question, undersea flows don't count. They are fascinating, but I'm interested if any "regular surface rivers" exist as saltwater rivers.

The water in any river draining the sea is infinitely recycle-able (from rain replenishment), whereas the salt from any terrestrial source is not. So salty rivers, if any, won't exist permanently. Saltwater lakes gain their salinity precisely because they have no outlet, so salt just gets concentrated by evaporation. I don't think there are any truly saline rivers throughout their entire length.

The nearest approximations I can think of are:

Rare ephemeral runoff from emergent salt domes in desert areas.
Freshwater rivers that drain into arid areas where combined evaporation and infiltration gradually reduces the flow to zero. These are more 'very brackish' than truly saline. The Amu Darya in Uzbekistan is one such example. I don't know the salinity of the Jordan as it enters the Dead Sea, but the river is reduced to almost nothing, whilst there are hypersaline springs, and sewage effluent from Amman draining into it.
The only river I can think of that is very highly mineralized from source to sea is only about 3 kilometres long. It is an unnamed river from the volcanic crater on Savo Island, in the Solomon Islands (Southwest Pacific). It is also acidic and boiling hot - quite literally, for most of it's length.


Round structure in southern United States Assuming here might be someone who knows something about this, I wanted to ask what is behind this round structure I have spotted today on Google Earth:

There seems to be a large (~200 km), nearly perfect half-circle covering the states of Alabama, Mississippi and Tennessee. How could this regular structure  possibly originate? I did some research on the web, but could not find anything. It looks a bit like an impact crater, but there is none listed in this location and especially of this large size. So how did this structure emerge?

This is a sedimentary sequence representing the shoreline of a Cretaceous-Paleogene inland sea, the Western Interior Seaway. You can look at the sequence of sediments laid down in the USGS Geological Map of North America. I recommend downloading the Southern Sheet in high resolution and the Explanation Sheet to explain what's going on.

The land use pattern as seen by other people answering this question is actually putting the effect in front of the cause; due to the nature of these sediments being a positive influence on the fertility of the land, it is more likely to be used for farming.


Why is there a bend in the Lomonosov Ridge? Why is there a bend in the Lomonosov Ridge?

This is a supplementary question to that asked by Sabre Tooth in What is the tectonic explanation for parallel ridges in the Arctic ocean

Firstly, just including the map of the ridges, in particular the Lomonosov Ridge and the characteristic bend visible near the North Pole:

Image Source

Based on magnetic anomaly observations, Cochran et al. (2006) theorise that the bend visible in the Lomonosov Ridge formed over a 3-6 million year period where there may have been a non-transform offset connecting a seafloor spreading region in the west Eurasian Basin with the continued continental rifting to the east, that continued propogating eastward resulting in the area of oblique spreading.

According to the Cochran et al. article, the tectonic spreading occurred around 53-56 million years ago, which according to models from Shephard et al. (2013) was associated with the opening of the Eurasia Basin.

Note: Cochran et al. refer to the eastern side as that on the Siberian side of the 'bend' and consequently, the western side being in the direction of North America.

Specifically, Cochran et al. conclude that

  The prominent bend in the Lomonosov Ridge near the Pole corresponds to an approximately 50 km offset in Marvin Spur. The offset of the marginal ridge is consistent with the presence of a short extensional segment located between two long transforms.

References

Cochran et al. 2006, Morphology and structure of the Lomonosov Ridge, Arctic Ocean, Geochemistry, Geophysics, Geosystems

Shephard et al. 2013, The tectonic evolution of the Arctic since Pangea breakup:
Integrating constraints from surface geology and geophysics
with mantle structure Earth-Science Reviews


Resource for scientific maps? I need an administrative division map of england for a motivation for some scientific workshop. I don't want to cite wikipedia for this. Sadly I can't find any official resources and I don't really know what sites are generally trusted or scientific.
Any tips? I hope this is the correct forum for this answer.

Most maps of Great Britain derive from the maps published by Her Majesty's Ordnance Survey.  The official website is https://www.ordnancesurvey.co.uk/ and the sales page says that for £23.99 you can get a 1 year subscription to a digital app that gives you the ability to export in the GPX digital format.
A crowd sourced version working on a map of the world is The Open Street Map Project.  This is equivalent to your rejected option of Wikipedia but I mention it for others that may land on this question.


How long does it take for the ocean conveyor to circulate? What is the period of the thermohaline circulation in the ocean? Obviously, individual particles may take longer or shorter, but what is the average for a small water parcel to do a full loop and end up back in the same place?

According to NOAA It takes almost a 1000 years to complete a cycle. I am not sure how accurate, or where the citation came from their information so take it with a grain of salt. Lecture notes from one of Columbia University's 2007 "The Climate System" class suggests this process takes between 100-1000 years. This paper says Thermohaline Circulation overturns deep water every 600 years or so.


Is the centre of Italy still at risk of earthquakes? I am working on a project which involves taking over a business based in Italy. It is a small village situated near Rieti (Sabina Hills) called Casperia and I am wondering if it is on a fault line? Is there a risk of having more quakes in the centre of Italy? It's a business in the tourism industry, so it is very important for me to find out about the risks before I go ahead... Any suggestions welcome.

Many thanks for your time.

Adeline

The Italian Civil Defense's map of earthquake risk zones shows Rieti in at best Zone 2, "Medium-high seismicity, quite strong earthquakes possible", and near or in Zone 1, "High or catastrophic seismicity, strong earthquakes possible".

The map of recent earthquakes in Rieti shows regular earthquake activity. Last year an earthquake killed hundreds in Rieti.

There was a famous long legal case in Italy over earthquake predictions and warnings.


Is the term "fertile ash" a misnomer? I understand that volcanic ash contains minerals and can make soil more fertile.

But I've also heard the term "fertile ash" in some documentary (I have forgotten in what context). Is that a scientific term, or a  misnomer?

The Oxford online dictionary contains the following definition of "fertile":

http://www.oxforddictionaries.com/definition/english/fertile

  1 (Of soil or land) producing or capable of producing abundant
  vegetation or crops: the fertile coastal plain

  1.1 Producing many new and inventive ideas: her fertile imagination

  1.2 (Of a situation) encouraging a particular activity or feeling: conditions at the time provided fertile ground for revolutionary
  movements

  2 (Of a person, animal, or plant) able to conceive young or produce
  seed.

  2.1 (Of a seed or egg) capable of becoming a new individual.

  2.2 Physics (Of nuclear material) able to become fissile by the capture of neutrons.

By that definition, ash alone cannot be described as fertile.

Perhaps a philosophical point, but if it's not valid according to this dictionary, and it's not a scientific term either, then I suppose it's more a question of correct English, so maybe I should reword my title to ask if it's a scientific term.

'Fertile ash' is not a scientific term, but neither is it a misnomer. Unless the ash is deposited really hot - hot enough for the particles to weld together as 'ignimbrite', then the ash deposit has high porosity and permeability. As soon as water infiltrates, the anhydrous minerals start weathering to clay - generally smectite, or mixed layer clays. This released aqueous magnesium, silica, and low concentrations of other elements crucuial to plants. Thus, both the texture and chemistry of volcanic ash is conducive to plant growth.

When the volcanic island of Surtsey emerged from the Atlantic, just south of Iceland, in the 1970s, plants started to establish themselves in the volcanic ash within a matter of months.


What is (negative) wind stress curl? I'm currently doing research for a paper in school where we need to research on a university-like level. When I read the paper Causes and impacts of the 2014 warm anomaly in the NE Pacific, I found the sentence:

  The wind stress curl was negative, which has precedence but is still quite unusual.

The wind stress curl was given as $-0.5*10^6 \ \text{N}*m^{-3}$. I neither know what wind stress curl is, nor what the negative sign is, nor what the unit of it exactly describes (of course, pressure per meter, but what does that mean?).

Can anyone explain what it is?

Skimming the paper, I believe the relevance of the wind stress curl is its relation to "Ekman pumping". I haven't found a simple, concise reference for this, but this page might be a good start, and this page has a couple of formulas about wind stress curl. I'll try to summarize here.

When wind blows over water, the top of the water starts moving. It shears against the water below it, so that water starts moving too. The momentum from the wind is transferred down into lower layers of the water. This water also feels the Coriolis force. The direction it ends up moving in depends on the balance of friction/drag and Coriolis force. On average, the water moves to the right of the wind in the northern hemisphere; if the wind is blowing northward, the water moves eastward.

Now imagine you have strong wind blowing northward at one location and weaker wind to the right of it. The water at the first location moves to the right, and it does so faster than the water at the second location (because the wind forcing the water is stronger at the first location). The water converges at the second location, pushing the water downward. This is how the curl of the wind stress (the northward wind changing in the east-west direction) is related to the water convergence (the eastward current changing in the east-west direction) and hence to water being pushed down or pulled up. Positive wind stress curl pulls water up; negative wind stress curl pushes it down.

The last relevant part here is that this kind of motion suppresses ocean mixing. The relevant sentence from that paper is

  The wind stress curl and hence Ekman pumping anomalies were negative, which also is consistent with relatively weak entrainment.

"Entrainment" is how much of the deep, cold ocean water mixes with the relatively warm upper ocean water, cooling it. The negative wind stress curl leads to water being pushed down and less deep water mixing with the upper ocean. The upper ocean stayed warmer, so the whole heat blob lasted longer.


Are there any flights that fly east both from origin to destination and from destination to origin? Flying east is faster so I expect that if the destination are on opposite points or closer, that the flights between them always be to the east.

For example Los Angeles to Delhi. I see the fly is over the north pole.

Wouldn't it be faster to always go east?

http://www.gcmap.com/mapui?P=lax-del&DU=mi

FlightAware suggests there are no non-stop flights from LA to Delhi.

Was certainly going to point out that we're pretty limited on ultra long-haul flights still, and it'd take a very special flight setup to make your scenario.  You'd need both:

Two locations about 180° longitude apart so that the distance going east vs. the distance going west is insignificant for both legs enough so the jet stream gains flying east pay off.
Two places at just the right latitudes.  They need to be at latitudes far enough south (in the NH) that it's not much shorter to just fly the great circle through the North Pole [or near if not 180° apart].
Here is a graph showing the ratio of the distances of the path crossing the Pole vs the distance of the constant-latitude path, for places 180° longitude apart [derivation in comments]... which shows it's 50% longer to fly around the 60° latitude circle than to fly over the Pole).
However, the further equatorward (south in the NH) you go, the less benefit you'd get from the jet stream as upper wind speeds are typically much slower further south, and you'd spend less of your flight time in the jet stream.  (Here's a current jet stream map).

Keep in mind that the jet stream is only going to add 100-200 mph in general.  So that's only like 1/3 of the cruising speed of a large jet.  Of course the benefits will show up in both in fuel usage (and the additional weight benefits of carrying less fuel) and in travel time (people like quicker flights, and you can run more flights in a year and/or pay crew less).  So despite being a longer distance, if it cut enough time/energy it might just be worth it.

And, well go figure, it turns out you weren't far off at all!  Because there actually is a direct flight from San Francisco to Delhi.  And it looks like they do exactly as you suggested!

(Click images for larger versions)

These are Air India flights 173 and 174.  The official flight does make a jaunt from Delhi to Bengaluru and back once it completes the SFO-DEL leg.  But you could indeed go around the world from Delhi to San Francisco to Delhi without any other stops... in looks like around 36 hours.

Pretty cool!


How to find the magnitude of earthquakes roughly if we know the Richter scale magnitude of epicenter? Please help me roughly estimate the magnitude of a quake at a distance d (for example 300km) from the epicenter if the magnitude at the epicenter is m (7 at richter scale) is known.

Your question cannot be answered with any accuracy because the result depends mainly on a key unknown parameter: hypocentral depth D.
To show this, let me use the empirical relationship known as the Lillie formula:

$$m = \log(A) - 2.48 + 2.76*log(d)$$

Where:

$m$ is the local magnitude (no units).

$A$ is the amplitude of the maximum ground displacement (in micrometers) of the P-wave, measured at 0.8 Hz.

$d$ is your epicentral distance in km for large distances (hundreds of km).

Note that for low values (when approaching the epicenter) the equation does not hold because the log tends to -inf. That's why these empirical formulas are only used  for long epicentral distances, not at local scale (and definitely not at the epicenter).

Following your example, if your earthquake is very shallow you would have a huge magnitude difference between your station at distance d and the epicenter, whereas if the hypocenter is 600 km deep, m will be very similar in both places.

So you need to know the depth of the earthquake to derive the magnitude in the epicenter.


In meteorology, are satellite data "better" than reanalysis data? More specifically, can it be argued that satellite data are more reliable because they are direct measurements of physical quantities, while reanalysis data depend on the processing and merging of different datasets ?

Unfortunately, your question has no answer. Both have errors. Both can be unreliable. Your choice really depends on how you plan on using them.
Satellites instrument contain sources of error, such as bad observations (wildfires in the NIR), mapping problems (especially near the poles), and representation error. Don't underestimate those sources of error- Geer and Bauer found that representation error can result in errors in brightness temperature larger than 20 K. Reanalysis combines both observation errors and model errors. A good reanalysis will reduce the influence of both errors, but it is still ingrained into the product. Satellites still report back observations.
Reanalyses can be unreliable. For example, this paper shows that TRMM and PERSIANN‐CDR were more reliable than CFSR or ERA-interim.
Maybe more significantly, they both actually report entirely different things. Satellites measure radiances which can be converted into more sensible variables, while reanalyses use a mathematical representation of the atmosphere and observations. So comparing these are a lot like comparing apples and oranges.
Some other thoughts you may want to consider:

Is balance more important than truth? Reanalyses tend to be more meteorologically complete, therefore balanced. Satellites actually observe the earth system, so they will be more grounded in reality.
What temporal resolution do you want? Reanalysis outputs are usually once every few hours, while the temporal resolution of satellites vary a large amount, in both number of observations per hour and when observations are taken (such as geostationary vs polar orbiting).
What horizontal resolution do you want? Satellites may have a horizontal resolution modelers can only dream of (metaphorically speaking), but at the cost of the number of regions (for polar orbiting satellites) or consistency (for geostationary satellites).
For what amount of time do you want data? The ERA-20C dataset can go back to 1900 and the NOAA/CIRES dataset goes back to 1850, while the first meteorological satellite was put up in 1959.


What is the rock I found on the Delaware river yesterday? I spotted this large striped rock found on Delaware River. Note the fossil in the first picture. What kind of rock is this?

The boulder appears to be dark grey  fossiliferous limestone or dolostone with softer tan layers which might be: limestone or calcareous claystone/siltstone/sandstone.
From the photo, the tan layers do not appear to be shale.

I have a hand specimen which is very similar from southern New Jersey.
It is harder grey limestone inter-layered with light tan calcareous siltstone.


How are tall cays formed? From reading about Cays on Wikipedia it seems they are formed from coral reefs covered with sand or gravel.  There are however some cays scattered around the world which are hundreds of feet off of sea level at high tide.  How did these cays form, or are they mis-classified islands?

its the same way atolls form, sea level changes and tectonic plates move while the corals keep growing up as the land sinks. Any spot high enough for coral to survive can slowly grow in this way. they can end up hundreds of meters above the sea floor by the slow gradual process of growing coral.
I find a simple animation makes it easier to follow.
Cays are just trapped sand in the coral reef, the sand can come from the erosion of nearby  islands, volcanic, or even erosion of the coral itself. This is why most cays occur near other land masses or in volcanically active areas.
Just as land can sink it can also rise, pushing those deposits high above the waterline, note these cays are very rare. Also note the parts far above the water are dead ancient corals not living ones, although there may be leaving coral around the base. there are ancient fossil corals in the Himalayas after all.


Permian-Triassic mass extinction. Consequences on Earth's system Coming from this post:

Causes of fluctuations in atmospheric oxygen in past 300 Mya

I believe there are a lot of questions still unanswered about Permian-Triassic mass extinction, but I ask only for its influence on the Carbon Cycle, atmosphere levels and climate in general.

What did the extinction change in Earth's system?
Did unicellular organisms restored some kind of new equilibrium?
What do we know?

Wow, I just finished watching this it seems we know, or can guess, quite a bit about the level of Carbon, particularly Methane that were released at the end of the Permian and what they did to the climate. What seems to be missing is any consensus about why the Permian extinction stopped just that once things settled down climate and atmosphere swung back to about where they'd been beforehand. Inference to best-guess? It was rain and rocks that did most of it, with the biosphere in such a mess and so much new surface rock in Siberia the main mechanism to remove Carbon from the atmosphere would be chemical weathering; the rain dissolves Methane and Carbon Dioxide forming complex acidic solutions that react with the fresh rock, this forms insoluble Carbonates which lock carbon in the ground.


What is an aurora called when viewed from space? An aurora is defined as a electromagnetic instance caused by polarization and ionization within a planet's higher altitudes. But what are the different phasics (beginning, middle and end) and perspectives (planetside/spaceside) of an aurora if observed from a 3 dimensional view.

The question: What is an aurora called when viewed from space?

It is still referred to as an 'aurora', examples include a relatively recent report from NASA - Stunning Aurora from Space.  Further, the aptly named document from NASA - Aurora - refers to the phenomenon by that name in reference to when it is observed from the surface or from space.

Whether viewed from the surface or from space, the phenomenon is still called an aurora.


Is it possible to find the magma chambers that produce supervolcanos? Supervolcanos have occurred in the recent geological past, but not within the past 74,000 years. Is it possible to find the magma chambers with no previous history of supervolcanic activity that are likely to produce supervolcanos?

I am a seismologist, not a volcanologist, but we can use a method called seismic tomography to understand the size of magma chambers.

This method is similar to a medical CT scan - the magma mush will have a slower seismic wavespeed than the surrounding 'normal' rock. Therefore, we can use this to determine the size of magma chambers from a tomographic image.

Even if a volcano does not appear to be active at the surface, it could still overlie a magmatic anomaly.

This approach was recently used to estimate the seismic of the Yellowstone magmatic body. See this paper: http://onlinelibrary.wiley.com/doi/10.1002/2014GL059588/abstract

Seismic tomography can theoretically be applied to any region, but we just need to have enough seismic sources nearby (e.g. earthquakes) to be able to do this accurately.


What is the difference between a geologist and a geophysicist? What are the main differences between geologists and geophysicists?

First of all you have to think about that both geology and geophysics are huge fields and even people that think of themselves as a geologist or geophysicist can have vastly different research topics.

If a geologist and a geophysicist are interested in the same topic, e.g. the lithosphere, they will have a lot in common. In this example I think the main differences would be methodology. While a geophysicist would rely on the analysis of seismic waves, numerical simulations and modelling, a geologists would work more with lithospheric scale cross sections, and geologic data that he or she can gather on the surface.

In summary I would say: The fields have much overlap, many differences, and when approaching a question more calculations and modelling will be done in geophysics and more field work and lab work (petrology, age dating, stratigraphic age, ...) will be done in geology.


Who originated Taylor's axiom of lunar formation, and where? I've been doing a bit of reading about the formation of the moon, and I've found multiple references (1, 2, 3) to something called Taylor's axiom, stated in link (3) above as:

  The best models for lunar origin are the testable ones.

A few related questions:

Who came up with it? If it was, in fact, someone named Taylor (which it need not be), which Taylor?
Is there a paper/talk/etc that contains a definitive form of Taylor's axiom?
I think we can all agree that testable models are the best ones. Why, then, did Taylor's axiom even need to be stated? e.g. was there a time when when untestable theories of lunar formation were in vogue or something?

Just a shot in the dark, as the journal in which this article has been published has no online presence and is not available in paper form in my institution, but it might refer to an article by a Richard L. S. Taylor from 1990 called 'The Damocles Hypothesis', published in the journal "Space" (journal edited by the University of London it seems).

Follows the abstract of that article:

  Consideration is given to the use of data from the Apollo missions to
  study theories of the origin and geological evolution of the moon.
  Theories of lunar origin are examined, including origin by fission,
  binary accretion origin, the capture hypothesis, and the giant impact
  model. Apollo data related to each of these theories is summarized,
  showing that the giant impact model is the most probable theory for
  the origin of the moon. The giant impact model is outlined, focusing
  on the collision between the earth and a large body called Damocles.