Will a new glacial age take place on Earth or Holocene will become a new climatic epoch?

The reason the Holocene began about 12000 years ago was because that was when Northern Hemisphere summers were hot but short. Those hot summers started a melting process.
Right now, July is when the Earth is furthest from the Sun. This makes Northern Hemisphere summers long but mild. That is one of the key conditions that enables a glaciation to start. In particular, glaciations start when summers at high northern latitudes are so mild that all of the snow that accumulated during the previous winter doesn't melt. This triggers a runaway effect by increasing the Earth's albedo. This means the next summer will be even cooler and even more snow and ice will accumulate. Even though we're right about when a glaciation would nominally start, that hasn't happened this time around because of a combination of a lowish eccentricity of the Earth's orbit and a lowish axial tilt (obliquity) of the Earth's orientation, and possibly because of human-generated CO2 concentrations in the atmosphere.
The Earth dodged a glaciation bullet this time around. The next chance for that bullet to hit (aphelion in late June / early July) will be 23 to 26 thousand years from now, and the next one after that, roughly 50 or so thousand years for now. From what I've read, eccentricity and obliquity conditions won't be quite conducive to see the onset of a glaciation the next time around, so the Earth will have to wait 50 or so thousand years to see the possibility of another glaciation.
While that isn't our problem, we can help our children's children's children's children's ... children (about 2000 generations worth) survive that potential glaciation threat 50 or so thousand years from now by leaving them with lots of carbon-containing resources to burn. They might well need those hydrocarbons to prevent a glaciation. As a double bonus, stopping burning those hydrocarbons now will make for a much better life for our current generation of children, for their children's children, and for their children's children's children (which brings us to about 2100).


Why does mineral oil occur below natural gas?

Natural gas can occur above and below oil formations however when they occur in the same formation natural gas will sit on top because it’s density per kg/m3 is 800+ and natural gases density is 400+

weight of natural gas

weight of crude oil


Assessing sea levels is a complicated business, as there are a number of factors which can affect sea level relative to a fixed point on land. For a start, land levels rise and fall; in some places land is lifted up by plate movements or volcanism, in other places  it may fall. Rising and falling atmospheric pressure makes very temporary local changes. The factor which causes the most concern these days is the rise in mean sea level caused by melting ice on land increasing the amount of water in the ocean. This has been going on since the end of the last ice age some 12,000 years ago, and is caused by global warming. This mean sea level is the one from which the height of mountains is calculated and the altitude of aeroplanes. Melting of sea ice causes no rise in mean sea level. Another factor is that, relieved of the burden of thousands of cubic km of ice at the end of the ice age, places like Scotland gradually rise up, and this rising of the land can persist for many thousands of years after the ice has vanished. In some places there is a seesaw movement where the rising of one part of a plate causes another part hundreds of miles away to descend.


Why during subsidence inversion, upper layer warms more than lower layer?

I assume that the sentence in the book mainly refers to subsidence as an adiabatic process. This sinking motion has a maximum which is at a height well above the surface, simply for the reason that air flow can not penetrate the earth's surface. Therefore maximum adiabatic heating rates occur well above the surface as well. The precise height where this occurs depends on the height of the planetary boundary layer, which itself depends on many more both adiabatic and diabatic effects.


Does a greenhouse need to be built on agricultural land?

Greenhouses can be built anywhere, so long as the plants within them are provided with sufficient nutrients and light. Depending on the crop, soil is not required if hydroponic methods are used.

The use of agricultural lands is not a requirement. In urban areas, disused warehouses and other buildings are used to establish vertical farms. Greenhouses are even placed on roofs of buildings.


Can ultrasounds be used to map the density of large underground regions?

Sound-like waves are routinely used to image the subsurface, but mostly well below the ultra-sound band.

Several methods involve sound-like vibrations:

Reflection seismic — the most important subsurface remote sensing tool we have
Refraction seismic — important, but niche, and has a lot in common with reflection
Acoustic logging — uses ultrasound, which you specifically asked about

What do you mean, 'sound-like'?

I say 'sound-like', because we normally think of sound as a vibration that we can hear, conducted through air or maybe water or building materials. In seismic methods — such as we might use prospecting for minerals, oil and gas, water, geothermal resources, etc. — we use very low frequencies, typically in the 4–256 Hz range (about 6 octaves). You can certainly hear some of these frequencies, but not those below about 20 Hz, which are often the strongest frequencies in our signal.

Why is seismic reflection such a big deal?

From thousands of field recordings, usually shot in a grid over a land or marine area, we can reconstruct an image of the subsurface using a process called tomography. The data might be 2D (a vertical cross-section) or 3D (a volume, analogous to a CAT scan). In some cases, this image is excellent and reveals a great deal about the geology of the region. Here's an example from a paper by Moore et al. (Science, November 2007):

How much can you see?

A large survey might be hundreds of square kilometres, or many tens of kilometres long in the case of 2D data. We can image well down to about 6–8 km, and we can image something down to about 20 km. The typical resolution of seismic is on the order of tens of metres horizontally and a few metres vertically (about a quarter of a wavelength). This is much better than gravity or magnetics. You might think, "Why not use higher frequencies for imaging — surely you'd see more?" Yes! We would love to use ultrasound (say) for imaging. The problem is that high frequencies are absorbed more efficiently by the medium (mostly rock and water) and actually heat it up very slightly.

What can you find out with sound?

In many cases, we can go beyond an image of the subsurface and deduce some physical properties of the earth, especially the speed of sound in the rock and the density of the rock. Sound reflections depend on changes in acoustic impedance, and are dependent on the incidence angle, so all the physics really stems from that relationship.

What about acoustic logging?

Acoustic logging or sonic logging is an important counterpart to seismic imaging, because the logs — run along a borehole using special tools — are the best link between the acoustic properties of the rock. They thus link us to the seismic image that depends on those acoustic properties. So we don't image anything with this data, because it's one dimensional, but it's a key calibration point. Acoustic logging does use ultrasound in the 20 kHz range, but the attenuation issue is not a problem in the vicinity of the borehole.


Although not a geologic map this site has a nice map of mines for silver, gold, copper, molybdenum, and zinc.  Below is a screenshot of just a portion of the pdf you can download.


In cities, is the pollution level higher on higher floors?

Yes, the higher floors will have less pollution than the street level.
The wind rises as a function of altitude, so the street will have less new air coming in, on average:

Some of the pollutants are lighter than air, i.e. Ozone, and some are heavier, i.e. particulate matter, they tend to rise or fall very slowly, so they can be slightly different gradients at different floors of the building.
The pollutants are diffuse clouds that rely on ambient air currents for dispersion.


Technical term for percentage of CO2 remaining in the atmosphere

We call this the airborne fraction, although as the name suggests, it's normally expressed as a fraction rather than a percentage.

Raupach et al (2014) is an (open access) example of it being used in the literature, and in that paper they quote a long-term 1959 to 2012 value of 0.44, so in the same ball-park as your estimate.  Similarly, here's an example of it's use in Chapter 7 of the IPCC AR4 with a range of modelled values from 0.4 to 0.5.  It's also often calculated over single years, as in your example, to look at the trends and variability.

As an aside, the 2 ppm in your calculation is called the atmospheric CO2 growth rate and the total mass of CO2 in the atmosphere would be the atmospheric CO2 burden.


OpenEEW - earthquake early warning by everyone?

In fact it is possible, the early warning system is not something more than a series of accelerometers (seismometers). There is always an epicenter for an earthquake. closer sensors to the epicenter shorten the time for occurrence announcement and more time for far locations to get ready.
There are even some efforts to use personal cellphones accelerometer sensors as a part of broad early warning system. for example here and here . RaspberryShake home sensors can also contribute in a global effort to shorten seismic events announcements. you can follow some live data shared by this home instruments in Iris jamaseis software, freely.
This should be noted that all these efforts are still in early stages. Currently some seismically active cities are equipped with early warning systems but not based on home sensors but on seismic networks.


How and why do these tree-like river structures form?

The river isn't splitting. The picture shows a number of dendritic drainage channels flowing into a larger river/stream. They are the most common form of topographical draining system. They develop in gently sloping topography and they ...

  develops in regions underlain by homogeneous material. That is, the subsurface geology has a similar resistance to weathering so there is no apparent control over the direction the tributaries take. Tributaries joining larger streams at acute angle (less than 90 degrees) [Earth Drainage Systems].

You'll notice in the picture all the drainage channels intersect the river at approximately 90 degrees. Also it appears the channels dendritic channels have formed in what looks like a sandy/silty sediment, again homogenous material.

Other sources that may be helpful:

Experiment to Examine Dendritic River Systems

Dendritic river flow simulations

Flow direction & branching geometry

Dendritic Design


Can El Niño and La Niña occur at the same time?

By definition, El Niño and La Niña cannot occur at the same time. They are instead opposite extreme phases of the El Niño Southern Oscillation.

El Niño conditions occur when the average temperature of the Niño 3.4 region is a half degree or more over the average for three consecutive months or more. La Niña conditions occur when the average temperature is a half degree or more below the average for three consecutive months or more. The reason for looking at a rather narrow band of the equatorial Pacific rather than looking at the Pacific as a whole is because of teleconnections. Whether El Niño, neutral, or La Niña conditions apply has wide ranging impacts across the globe.


Are wetlands effective against climate change?

There's a misinterpretation in the "steady state" part, that's not what the linked paper says. It clearly states the figures are temperature dependent, and it says that in response to global warming wetlands are going to release more Methane and tries to quantify the amount. It concludes that

This finding highlights the importance of limiting global warming below 2°C to avoid substantial climate feedbacks driven by methane emissions from natural wetlands.

'Feedback' is the keyword here. Such a feedback is an accelerated response of a system to global warming. Grossly simplifying, in case of small shallow wetlands CH4 release is connected to the level of oxic and anoxic conditions, the latter expanding not only in the table of a local 'puddle' but also geographically from lower to higher latitudes with temperature and so releasing more CH4 in a warmer climate, which warms the climate and so on. But the ability of these ecosystems to bind carbon from the atmosphere drops with rising temperature, and the amount of released carbon rises.
That is by no means an argument against the conservationists who are advocating conservation and re-valuation to help sequester carbon.

This analysis can help inform practitioners and landscape managers [...] foster the worldwide implementation of wetland restoration, creation, and conservation projects for sustainable development and climate change mitigation and adaptation.

So, yes, for now wetlands are effective against climate change as long as anthropogenic global warming is limited.


Performing time-frequency analysis (FTAN)

If you are flexible with your choice in software, I would strongly recommend using Bob Herrmann's Computer Programs in Seismology for this work. http://www.eas.slu.edu/eqc/eqccps.html. This software package has nice workflows for doing ambient noise tomography and will save you a lot of time over python. For example, you can relatively quickly do group/phase velocity dispersion curve picks. It is also fairly easy to QC your data. Look at the documentation for 'Surface Wave Dispersion - Receiver Function Inversion' on http://www.eas.slu.edu/eqc/eqc_cps/CPS/CPS330.html for more details.

If you must use python, I would suggest writing your own Time-Frequency code as obspy's implementation is not very thoroughly documented, and you still need to get from Obspy's representation to dispersion curves. This will take some time, especially if you want a nice GUI for picking. This is why I recommenced the aforementioned software.


There are about 3 tonnes of uranium in every cubic kilometre of seawater, but in the general circulation there is no mechanism to concentrate the uranium, except perhaps low-level adsorption on manganese nodules in some parts of the sea bed. To concentrate the uranium you need some mechanism to transport it, and some other mechanism to make it precipitate. Both are pH-redox controlled, requiring substantial reducing conditions. The nearest plausible mechanism I can think of is a high concentration of uranium in groundwater, such as in the Aktau province of Kazakhstan, adjacent to the Caspian Sea. At present the Caspian is too oxygenated, and is likely to remain that way because of inflow from the Volga, but if climate change alters the rainfall-runoff relationship then that inflow to the Caspian would be reduced. Conceivably, it wouldn't take too much more pollution and reduced river inflow to make the deeper parts of the northern Caspian more reducing. Then maybe you could get uranium deposition at the groundwater-lakewater interface.


How does a whirling hygrometer work, how does it differ from static dry/wet bulb thermometer, and how to obtain humidity from its readings?

Instead of «whirling thermometer» you probably refer to «sling psychrometer» consisting of a dry-bulb thermometer and a wet-bulb thermometer.  Yet, different to a static wet-bulb thermometer shown in the question, the constant rotation of the two thermometers permits evaporation from the wet cloth around the web bulb thermometer to «pristine parts» of surrounding air.

(credit)
If the air around the wet-bulb thermometer is less than water saturated, the temperature of shown on the wet-bulb thermometer will be lower than the one read on the dry-bulb thermometer.  The swirling motion aims to expose the wet-bulb thermometer to air which was not yet in contact with the former.  Thus, both recordings allow you to report both (dry) temperature, dew temperature, and humidity of the air.
A beginner's introduction is equally given here, a computation chart relating the temperature difference read (one for the Celsius, an other for the Fahrenheit scale) to the relative humidity here.

Suggested by user @uhoh, it is worth to set the quality of the readings obtained with this instrument into a context.
The 1993 edition of Conserve O Gram 3/1 (accessed from the series' program overview) mentions «These instruments are accurate to $\pm \pu{2\% RH}$ when properly maintained and operated by trained and practiced users.»  Equally, the guide reminds to the Clausius-Clapeyron relation when stating:

«Psychrometers and psychrometric charts are intended for use within a certain range of atmospheric pressure. High altitude, above 900 m (approx. 3,000 ft), will directly affect the accuracy of the RH reading unless a pressure correction formula is applied or a psychrometric chart or slide rule for the appropriate pressure is used. For further information see Ann Hitchcock and Gordon C. Jacoby, “Measurement of Relative Humidity in Museums at High Altitude,” Studies in Conservation 25 (1980): pp. 78-86. (Copies are available to NPS sites from Curatorial Services Division, Harpers Ferry office.»

A study by Wang and Tang /  Singapore's metrology centre published by 2007 mentions:

«... that although the psychrometer coefficient of a particular psychrometer can be quite consistent with long-term stability typically within the range of  ± 1% rh equivalent, there are larger variations (up to 4% rh equivalent) among different psychrometers even of the same type.»


How does temperature impact the elevation distribution of orographic precipitation?

Examining two extreme cases, one very cold and the other very warm, the amount of precipitable water in the very cold one will be far less than that in the very warm one.  Even fully saturated, the very cold air mass would need to be lifted quite high to form large enough ice crystals or water droplets to have enough mass to begin falling.  Meanwhile, the warm air mass would produce larger droplets very quickly.  Thus the warm air mass would begin to produce precipitation at a lower altitude, and with greater intensity.

Because the air masses begin precipitating at different altitudes, the point of maximum intensity would also be lower for the warm air mass.


What does it mean when the depth of earthquakes get near the surface over a period of time?

The data from USGS is somewhat misleading.

Determining earthquake depths is a difficult problem, particularly if you're using data recorded a long way from the earthquake. Event location methods often become unstable for very shallow earthquakes. With some methods/catalogues it is therefore normal to "fix" the depth of shallow earthquakes, and not attempt to find a more accurate depth. This is why you see so many earthquakes supposedly at 33km; I think the 10km ones may also be fixed. Really, this ought to be made more obvious in the USGS site (I think the information is there if you dig deep enough!).

So, it's impossible to draw any conclusions from these graphs: you're probably just seeing improvements in seismological techniques over time.


What is serpentinization, in the context of disappearance of surface water on Mars?

does serpentinization just refer to the formation of some hydrated minerals that happen to be of a class that is historically been referred to as serpentinite or it's subgroup

Yes. In simple terms, the reaction is enstatite + forsterite + water = serpentine.
MgSiO3 + Mg2SiO4 + 2H2O = Mg3Si2O5(OH)4
Forsterite and enstatite (or more generally, olivine and pyroxene) are common minerals in mafic igneous rocks. The formation of serpentine locks up water in the resulting solid crystal structure.
You can see more examples of serpentine forming reactions on page 5 of this PDF file.

or is serpentinization a process that always produces serpentine patterns?

No. There is no such thing as "serpentine patterns". The image you link to is of "folded serpentinite". The "serpentinite" bit of it are the green layers, regardless of whether they are folded or  not. The nice photogenic folded part is a later tectonic event that is unrelated to the formation of the serpentinite.


Where can I find detailed historical breakdowns of U.S. lightning fatalities on a year-by-year basis?

For a comprehensive literature review of sources of lightning fatalities data you can check the paper "Striking Back: An Assessment of Lightning related Fatality and Injury Risk in Canada", it covers US and Canadian sources. But if you want to know which one is the largest and arguably the best. That would be NOAA's Storm Database. The data you can access trough the online interface is quite limited, so I would recommend to go to the Bulk Data Download area, and get the original spreadsheets. You will see 3 files per year: Locations, Fatalities and Details, from 1950 to 2017. I would recommend to download the "Details" files, as it also have information about the location (Lat/Lon) and number of deaths and injuries, and a short narrative of the event.
It is a large table, as an example, I took the following screenshot of the most important data columns for all the lightning events with casualties in 2009:

You can download the Fatalities file if you want more info abut the age, gender and location of the victim. The relevant fields look like this:


What is the appropriate vertical datum to use globally?

In a recent study, Talone et al. (2014) compare 4 different geoids and evaluate their effects for oceanographic studies. The four geoids they used are:

  EGM96: The Earth Geopotential Model 1996 embodies ground-based as well as satellite measurements (Lemoine et al. 1998). Remotely sensed data were mainly radar altimeter observations, averaged and transformed in gravity anomalies as expressed in Sandwell and Smith (1997). This geoid may be downloaded from the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center web page (http://cddis.gsfc.nasa.gov/926/egm96/egm96.html). In this study a 360-degree and -order version of the EGM96, included in the GOCE User Toolbox (GUT), was used. GUT is distributed by the ESA at http://earth.esa.int/gut/. In the spatial domain, the geoid is defined on a 0.5° uniform grid. Since the calculation of the EGM96 geoid included altimetry measurements, we may expect that it might have been influenced by some signal from the MSS fields.
  GRACE05: The Gravity Recovery and Climate Experiment (GRACE) (Tapley et al. 2004) is a joint mission by the American (NASA) and the German (DLR) space agencies, launched in March 2002 with the objective of making detailed measurements of the Earth’s gravity field. GRACE’s data are available on the web pages of these two institutions (http://podaac.jpl.nasa.gov/grace and http://isdc.gfz-potsdam.de/grace). As for EGM96, the GRACE05 geoid used in this study is included in the GUT (see Foerste et al. [2008]). It is characterized by a spatial resolution of 0.5° and a spherical harmonic degree and order 360. GRACE05, in the version used for this study, includes altimetry measurements.
  EGM2008: The Earth Gravitational Model 2008 is described in Pavlis et al. (2008) and distributed by the International Centre for Global Gravity Field Models (http://icgem.gfz-potsdam.de/ICGEM/shms/egm2008.gfc). It is available up to spherical harmonic degree and order 2159, and contains additional coefficients extending to degree 2190 and order 2159. For consistency with the EGM96 and GRACE05, the geoid heights have been calculated using up to the spherical harmonic degree and order 360, with a spatial resolution of 0.5°. Like EGM96, EGM2008 is the outcome of fusing different data from several sources, including altimetry data.
  GOCE’s level 2 time-wise product: The time-wise product is obtained using only direct measurements of the gravity field, without any altimetry contribution. Details about the GOCE mission can be found on the ESA web page (http://earth.esa.int/GOCE) and in the ESA (1999) report; data may be accessed on the ESA web page. Three different products are available, namely the direct solution, the space-wise solution and the time-wise solution; the last of these was used in this study as it does not rely on auxiliary information (EGG-C 2012). We used the third release, the last one available at the time of the study, based on 16 months of data collected over 18 months (from November 2009 to April 2011). The spatial resolution of the GOCE level 2 products is 0.5°, with degree and order 250.

Talone, M., Meloni, M., Pelegri, J. L., Rosell-Fieschi, M., & Flobergaghen, R. (2014). Evolution of geoids in recent years and its impact on oceanography. Scientia Marina, 78(2), 155-164.


Where can fluorite be found on Long Island, New York?

I do not know of fluorite being reported to occur on Long Island. If fluorite is found in NYC, the Natural History museum might have specimens.  You might try contacting a mineralogy / mineral collecting club on Long Island. Someone there would probably know for certain if fluorite can be found.

Fluorite can be found in several limestone formations in New York. See map

Personally, I have collected fluorite from the Penfield Quarry near Webster New York during the mid 1980s.  Some of the waste rock from the quarry was used as breaker wall stone on the lake front in Webster New York.  You could probably still collect fluorite crystals there.

Here is a map of the lower 48 states showing mines where fluorite has been reported to occur.

Other places I have personally collected fluorite

Terlingua, Texas fluorspar mine (massive bedded fluorite)
Spearfish Canyon Black Hills South Dakota (fluorite in geodes in limestone)
Closed rock quarry in Pennsylvania near Breezewood, PA

Locations where fluorite is still able to be collected.

Mines/Mountains near Socorro New Mexico
Mt Antero in Colorado, at high elevation.
Bancroft Ontario - fluorite in calcite (fluorspar)
Burin Peninsula, Newfoundland, Canada (fluorspar)

References:

Wikipedia Fluorite

Maps created using  Digital Rockhounds Companion software.


tl,dr: low albedo = warming (more energy absorbed); high albedo = cooling (more energy reflected).

In principle, and grossly simplifying, energy from the sun warms the ground and less the air. The overlying air is then warmed by the ground, leading to convection, pressure differences, and all that.

So, a high albedo atmosphere would prevent sunlight from reaching the ground, having a cooling effect. Equally, a high albedo ground would reflect more sunlight, less warming the air. That's why glaciers or pole caps of ice have a feedback effect on cooling.

Furthermore, wavelengths reflected by clouds can help cooling an area by day, but also trap warmth radiating from the ground when they move over it. That depends on the situation.

A low albedo atmosphere would let more sunlight pass. In conjunction with a low albedo ground it has a warming effect. Again a potential feedback when ice starts to melt and exposes more ground, leading to more warming, etc.

An open sky will allow warming of the ground by day, but also partly cools back to space by night (continental or desert climate). Greenhouse gases are those that reflect this emitted radiation back instead of letting it escape into space.

Highly populated areas can have a "heat island effect", because of the low albedo of asphalt and concrete and the lack of plants and foliage to absorb sunlight for photosynthesis and evaporate ground water and thus cool.

That (highly controversial and IMO only driven by economic interest) geoengineering thing is about raising the albedo of the stratosphere in order to reflect more sunlight before it reaches the ground. Its adverse effects on ocean acidification and damage to marine life and terrestrial plants and animals ("acid rain") and unresolved side effects could outweigh the potential benefits. But that is a discussion on its own, IMO.

Hope that helps.


How is climate change today different than the climate change that ended the ice age(s)?

Difference #1: Speed. The warming at the end of the ice ages went much, much slower than what we are currently experiencing.
Estimates of the amount of warming since the beginning of the industrial revolution are in the order or 1 degree Celsius* - that's in 100-150 years time.
* Page 7

When the Earth moved out of ice ages over the past million years, the global temperature rose a total of 4 to 7 degrees Celsius over about 5,000 years.

(NASA Source: How is Today’s Warming Different from the Past?)
The article Earth is warming 50x faster than when it comes out of an ice age sums it up nicely:

What humans are in the process of doing to the climate makes the transition out of the last ice age look like a casual stroll through the park. We’re already warming the Earth about 20 times faster than during the ice age transition, and over the next century that rate could increase to 50 times faster or more. We’re in the process of destabilizing the global climate far more quickly than happens even in some of the most severe natural climate change events.
That rapid climate destabilization is what has climate scientists worried. It’s faster than many species can adapt to, and could therefore cause widespread extinctions, among other dangerous climate change consequences. Coastal flooding in places like Florida has already become much more common than it was just 50 years ago, and sea level rise is expected to keep accelerating.

Difference #2: Civilization. At the end of the ice ages we did not have 3 billion people living within 200 km from a coast line
That is not an difference in the cause of the warming, but definitely in the effect.
One could argue that that same civilization will make us able to deal with the consequences, but looking at thing that already exists several centuries without change, surely raises doubts to our ability to deal with the current rate of climate change. Think (1) unequal global wealth distribution or (2) the psychology of our behavior (denial, politics).

BTW The question asked to you

If climate change is not a natural phenomenon, then how did the last ice age end?

is based on a false premise - it's a bit of a word game.
The current warming is still a natural phenomenon, but it's now primarily driven by our input, and not other 'natural' phenomena.


Is there a convenient place to get vertical wind shear info for my location?

Yes, NOAA's Storm Prediction Center's soundings page is a great source for the information you are looking for, especially the skew-T diagrams and wind hodographs. This site provides current soundings as well as a past archive of 1 week. For the explanation of the soundings diagrams and numbers provided, see the soundings help page.


Wind speed, precipitation, extreme daily precipitation

Sometimes it is obvious, but it may not be possible to attribute the rainfall mechanism from the daily rainfall. Also, the four lifting mechanisms are not 'either / or'. There are frequently combinations of the above, particularly in respect of the most extreme events.


I believe Manual of Mineralogy (based on Dana) is a good start for mineralogy and crystallography subjects. It is a good manual to understand the basics behind crystalls and minerals. It is a bit theoric, but it explain crystallography laws you need to know to face microscope. It also list the minerals by groups following Dana classification.

I would recommend to chose recent introduction books to get a view about Earth Sciences in general, as modern tectonics has changed some concepts. That will cost you some chips; if that's a trouble, university libraries use to be open to public. You can go there and read any book published recently whose title look like "Introduction to Earth Sciences". There are some books that specifically have a geophysics approach.

Talking about studying geology at a post-secondary level would be like, you need to know in geology field is the lab. In firsts courses you might find difficult to get it, but once you got the basic concepts, you will start to enjoy the Friday trips.

I am going to recommend, if you have the opportunity, to join a geology summer camp. You can ask at the university you want to join if they have field introductory courses. You will need good shoes, a geology hammer, a compass, a magnifying glass and good attitude to learn new things.


Transmitter receiver coil separation for Electromagnetic Terrain Conductivity Measurement

As described in the question there are two similar coils, one radiates the AC magnetic field ("transmitter") and the other picks up the weak radiated AC magnetic field produced by subsurface electrical currents induced by the primary field.

Sensitivity vs. Depth

There are two modes of operation. The following two figures are from Section 4.1 of GEONICS Technical note #6; Electromagnetic Terrain Conductivity Measurement at Low Induction Numbers. (more technical notes here) In both figures the two coils are separated by a horizontal distance $s$ which is typically a few meters.

In Horizontal mode the axes of the two coils point in the horizontal plane. In this orientation the sensitivity always peaks near the surface, and falls off to about 30% at a depth of $0.4 s$.

In Vertical mode the axes of the two coils point "up" or vertically. In this orientation the sensitivity is low near the surface and peaks at depth of $0.4 s$.

In either case, if $s$ is twice as big (the coils are twice as far apart) these two shapes will be stretched by the same amount. If $s$ is 2 meters, the vertical method will have peak sensitivity at 0.8 meters. If $s$ is 5 meters, vertical sensitivity peaks at 2.0 meters.

The two plots can be seen on the right side of Figure 1. in The Application of EM38: Determination of Soil Parameters, Selection of Soil Sampling Points and Use in Agriculture and Archaeology Kurt Heil and Urs Schmidhalter, Sensors 2017, 17(11), 2540; https://doi.org/10.3390/s17112540

That article also links to Comparison of the EM38 and EM38-MK2 electromagnetic induction-based sensors for spatial soil analysis at field scale which may cite further references but it's paywalled.

  Figure 1. (Left) Relative cumulative contribution vs depth for vertically (RV(z)) and horizontally (RH(z)) orientated dipoles; (Right) Comparison of the relative responses for vertically (FV(z)) and horizontally (FH(z)) oriented dipoles.

Yes, that's all fine and dandy... But Why?

I can't come up with a simple model for why this is true, so I'll have to read further. It's possible someone else will be able to provide a better answer. I think it's related to how the phase of the signals are process, but I'm not sure about that yet.

However, the Computers and Electronics in Agriculture paper Accuracy issues in electromagnetic induction sensing of soil electrical conductivity for precision agriculture (also available here) K.A.Sudduth, S.T.Drummond and N.R.Kitchen, Volume 31, Issue 3, May 2001, Pages 239-264 https://doi.org/10.1016/S0168-1699(00)00185-X happens to give equations for these shape, and a clue to where these are from.

Those equations are close but $\color{red}{wrong!!}$ they are missing a division "/" sign.

  Fig. 2. Relative response of EM38 sensor as a function of distance (adapted from McNeill, 1992).

The equations in the figure have obviously been typed incorrectly, but if I make some simple adjustments they work nicely

$$\phi_V(z) = \frac{4z}{(4z^2+1)^{3/2}} $$

$$\phi_H(z) = 2 - \frac{4z}{(4z^2+1)^{1/2}} $$

where z has to be unitless, so is almost certainly given by:

$$z \equiv \frac{\text{depth}}{s}$$

where $s$ is the separation between the two coils as before.

Possibly helpful links:

The use of electromagnetic induction techniques in soils studies (also available here)
Comparison of Electromagnetic Induction and Direct Sensing of Soil
Electrical Conductivity


Data source of the planetary boundary layer (PBL)

Not exactly. The PBL is a quantity more or less derived. you may be able to derive it from upper air observations, but a direct observation of it is not yet available. Here are some methods: https://e-reports-ext.llnl.gov/pdf/235179.pdf

The question you are asking is the equivalent of "Can we observe the Jet stream?" We cannot observe the jet stream, but we can observe the winds, from which we infer the jet stream.


Can I regard the grayscale of a RGB color image as a panchromatic image?

The workflow of fusing RGB true color image and panchromatic grayscale image can help understand this question. After converting RGB color space to the IHS space, the intensity component is replaced with the (high-resolutional) panchromatic image, and then the new intensity, hue, saturation combination as IHS are converted back to the original RGB space.


My best guess is a weathered dolostone. These are called dolomites in parts of the country (as around where I grew up) but dolomite is technically the name of the primary mineral in dolostones.  The visual clues I used were 1) it looks like weathered cobbles of the Alibates Dolomite which is common where I live, it is white which is a good color for a reasonably pure sample of dolomite, though I have no idea what the black stain or inclusion is), it is fine grain texture, appears to have a  laminar or bedded structure (but not the horizontal laminations or planer laminations of clastic sedimentary rocks), it appears to be chemically susceptible to chemical weathering but not so much so that there are big holes or gaps in it. The dark areas could be flint or chert.  I believe flint/chert is a common rock type in at least some dolomites, I know they are in the Alibates.
   Yes, try a drop or two of dilute hydrochloric acid if you have some,use vinegar if you don't. In fact  vinegar is probably the better choice for a person no accustomed to working with acids on rocks.  If the rock is limestone it will effervesce if it is dolomite it might dissolve a bit after a few minutes.  If you use they HCL and the  rock is limestone it will effervesce rapidly, if it is dolomite it may bubble a bit.
If you have HCL around the house it may be called muriatic acid and have been purchased at swimming pool supply store.  If you use that, be very,very careful!!. In fact I would not recommend you use it at all.  vinegar is much safer.


Carbon Dioxide levels appear to be linked to the Milankovitch cycles according to Ice Core data but what is the mechanism?

The link between orbital parameters and CO2 levels is, as you wrote, the temperature.

Orbital parameters may change, via feedback mechanisms, the atmospheric temperature. To my knowledge the most important feedback mechanism with respect to the Milankovich cycles is the ice-albedo feedback.

The temperature, however, is an important player in geochemical feedbacks which influence the concentration of gases like CO2 or methane. For CO2, again to my knowledge, you named the most important feedback; the exchange of CO2 between atmosphere and ocean.

The exchange of CO2 between ocean and atmosphere in turn depends on the partial pressure of CO2 in the atmosphere and the surface layer of the ocean; there is uptake, release according to the pressure gradient.
Now, the partial pressure of CO2 in the surface layer depends also on the amount of carbon transported or received from the deep sea layers. There is way more CO2 stored in the cold water of the deep sea. So the exchange of CO2 does depend on the vertical circulation pattern of the ocean.

There are, to my knowledge, three major mechanisms that transport carbon between the surface and the deep sea and they all depend on temperature.

Solubility pump: Cold water can store more CO2 than warm water. Therefore at the poles, where cold water is sinking into the deep sea, you have CO2 rich water. The CO2 stored in the deep sea can, as far as I know, remain there for hundreds of years, before it comes up again in the warmer upwelling regions at the equator. The temperature dependence of that mechanism is obvious.

Biological pump: In the surface layer you have photosynthesis of algeas etc., so carbon is withdrawn from the layer and stored in biomass. A portion of dead plants is not reused (eaten) but sinks into the deep sea. The process is temperature dependend since biological activity depends on temperature.

Carbonate pump: The amount of carbonate and CO2 are linked to each other via marine chemistry. Animals building shells etc. need carbonate thereby also influencing the amount of CO2 present in the water. Again, a portion of this carbonate is withdrawn from the short term cycles once the animals die and sink to the deep sea. Again this mechanism is temperature dependend since biological activity is.


Impossible or improbable? Hurricane crossing the equator

Improbable.

It is well known that the Coriolis force is needed to form a hurricane, and the figure of 5oN/S as the minimum for formation is widely publicized. You can also find record of tropical storm formation near India as far south as 1.4oN.

The problem of crossing the Equator isn't one of hurricane formation though, it is one of hurricane motion.  Due to Coriolis, a hurricane initially moving parallel to the Equator will start gaining a poleward component to its motion, thus moving it away from the Equator.  But, because this is due to Coriolis, if you could get a storm close enough to the Equator, this effect would not be as strong.  This would be an improbable track, but I'm not willing to call it impossible.  We haven't had satellites all that long, and all we can really say is that it hasn't happened since we've been watching.

If a storm did cross the equator though, what would it do?  Nothing at first, but as it moved further into the opposite hemisphere, Coriolis would be working against the storm and it would spin down, become disorganized and cease to be a hurricane, probably becoming a remnant low.

A tropical disturbance has crossed the equator.  One such disturbance occurred June 27, 2008 in the Atlantic basin (south to north) that retained its clockwise motion for some time:


Considering how old the Antarctic ice cover is, why isn't it much thicker?

Ice floats with gravity towards lower elevation, the flow continues until the base of the ice sheet becomes floating and the ice forms an ice shelf or icebergs.

Due to the subglacial topography, basal melting and mass balance, the flow velocities vary over a large range, faster outflows are glaciers. The pattern is somehow similar to how rivers transport rainwater towards the coasts.

The thickness of the ice sheet is controlled by a complex relation between accumulation, ablation and compaction.

Flow velocities from MEaSUREs (NASA), plotted from Quantarctica

The ice velocity map shows, that some areas are unaffected by the flow towards the coast. Some of these areas are ice-free. Also at some inland locations, as Vostok, the velocity is very slow. Also, note that this is the surface velocity. At the base, the ice flows slower or not at all.

To investigate the mass balance further, I recommended you to download Quantarctica and look closer at the datasets. Shepherd et al (2012) is a good first read about the methods used to estimate changes in ice mass and the present changes.


How to interpret hourly precipitation forecast?

The probability of precipitation is most likely to mean the proportion of models in an ensemble or weather models in which precipitation was observed at a particular location over a particular time period.
If you want to work out the probability of it raining during the day, the best approach would be to work out one minus the probability that there was no rain in hour one and there was no rain in hour two and there was no rain in hour three...  Mathematically if $x_i$ represents the presence or absence of rain in hour $i$, then
$P(rain) = 1 - \prod_{i=1}^{24} (1 - P(x_i = 1))$
However, this assumes that the probabilities of rain in each hour are independent, which is unlikely to be true.  To deal with this, we would need to introduce conditional probabilities (which are not supplied by the forecast), i.e.
$P(rain) = 1 - (1 - p(x_1=1)\times(1 - p(x_2=1|x_1))\times(1 - p(x_3=1|x_1,x_2))\times \cdot \times(1 - p(x_{24}=1|x_1,x_2,\ldots,x_{22},x_{23})$
So unfortunately you will not be easily able to reconcile the daily and hourly probabilities as this would require the conditional probabilities (or at least a model of the dependence), which probably is not supplied in the forecast.
In the particular example given in the question, if there were four hours that had a probability of rainfall of 50% then this could mean that 50 out of 100 models in the forecast ensemble had rain that lasted all four hours and the other 50 were dry.  However, it could have meant that 50 models have rain for the first two hours and dry after that, and the other fifty were dry for two hours and then had rain for two hours.  In the first case, the probability of there being rain at some point during the four hours is 50% (as half of the models say there will be no rain at any point) whereas in the second case, the chance of rainfall at some point will be 100% as all the models agree that it will rain during the four hour period, they just disagree as to precisely when it will happen.  The daily forecast works this out by looking at the proportion of models that actually gave some precipitation at some point during the day, but the hourly probabilities in isolation don't give enough information to work out what happened throughout the day in individual model runs.


Is there a quick way to roughly estimate how quickly a flood will move downstream?

My first thought would be to use Manning equation as an approximation. It does not take into account the effect of a dam burst providing excess water and immediate flooding, although for larger scales (in terms of river reach) this is likely less important.

Detailed hydrologic models may not be the right answer by the way, especially for the tradeoff of the work involved to build them. A detailed forecasting system with a model and real-time data would be the best, but a quick approximation is often a good guess for the work involved.


Why deep ocean didn't freeze during snowball Earth?

At least four things combined to prevent solid freeze-up during Ice/Slush Ball Earth periods:

It takes a lower temperature to freeze water under pressure. Deep sea pressures are enormous.
Ice floats. If it sank and new ice kept forming at surface, the seas might fill with ice.
The surface freezes first and acts as an approx zero-degree C barrier, slowing the progress of the ice penetration.
Thermal heat from the ocean floor at hotspots, island arcs, subduction zones, and mid-oceanic rifts is substantial, especially locally.


In my experience $[m^{-3}]$ or $[cm^{-3}]$ as number density is very well understood throughout the communities of both earth, solar-system as well as exoplanetary scientists.

Take for example the recently published The atmosphere of Pluto as observed by New Horizons which in fig. 3 shows the derived atmospheric composition of Pluto from occultation measurments in $[cm^{-3}]$ with some model curves:

 (Property of G. R. Gladstone et. al 2016 and the New Horizons Science team)

The density in this unit is just a very natural and convenient outcome of the used occultation-inversion techniques. Thus of course the units are sometimes simply the result of the context in which a work is done, and as other commentators stated, a mole could be used.
However I'd argue that $[cm^{-3}]$ is sufficiently simple to be understood in any context and adding moles just makes things unnecessary confusing as it suggests numbers to have a unit, which they don't.
It just physically makes no sense.


Relation between Magnitude of Greenhouse Effect and the Concentration of GHGs like $CO_2$

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.


The answer is that we don't know. I could give you a list of all the considerations that go into evaluating that question, but it will probably be incomplete and outdated very soon. There were several important papers published in the recent years, including some very readable reviews that you might be interested in (1 2 3). But, there isn't a consensus. A friend just had a paper accepted in which she shows Yet-Another-Breakthrough™ in this field.

However, the general idea is that most of the continental lithosphere formed early on (Hadean to Archean) and since then the rate has slowed down.

Continental crust forms, as you said, by formation of "lighter stuff". Melting ultramafic mantle rocks leads to formation of basalt, and further melting of basalt leads to granites (and other related rocks) which are indeed lighter in colour, and also lighter in density so they end up at the top, and then "float" as the continental lithosphere on top of the mantle. The problem is that you can also remelt over and over again the continental lithosphere, recycling the already buoyant rocks and not increasing the net volume of the continents. It's this balance which is unknown. How much lithosphere is "juvenile" (i.e. formed by melting of mantle) and how much is recycled.

To make matters worse, continental lithosphere can also be destroyed. The most obvious case is erosion from the continents which then settles as a thin sedimentary cover on the oceanic crust and then lost to the mantle during subduction. Another process is delamination. Some rocks such as basalt are normally less dense than the mantle rocks. However, when metamorphosed at high pressure to become eclogite, they paradoxically become denser than the mantle, leading to the bottom part of the lithosphere to be "ripped off" and sink down into the mantle, thus destroying the continental lithosphere from the bottom. Here's a nice visualisation of this process:

Source for the image.


The formation of quartz veins needs fluids enriched in Si. Usually Si dissolves somewhere in neighbouring formations, gets transported by fluids and precipitates where the fluid pressure is low (the fluids Si-saturation capacity decreases with decreasing fluid pressure).
Fluid pressure is usually involved in rock fracturing. When it builts-up, it can fracture the rock. Thereby generated fractures, in turn, accomodate void space, hence the fluid pressure drops and Si precipitates from the fluid to form veins. These veins reseal and restrengthen the rock, which can again lead to a renewed fluid pressure built-up. This process is known as crack-seal vein formation.

Usually, crack-seal vein formation happens progressively, which is a very nice thing: Studying vein internal mineral structures gives evidence to past stress regime conditions. These evidences can help unraveling the evolution of tectonic structures, such as mountain formations or fault systems.

Quartz veins are very common, they need a source of disolvable Si, which is a really abundant element. In carbonate rocks, calcite veins are more common. The crack-seal principle applies for them just the same.

Yes, you can see veins in satelite pictures! Have a look here: OMAN (These are calcite veins standing out against a darker limestone).

Hope this helps,
Ben

P.S.: You might want to have a look at my thesis on (calcite) vein-networks in Oman: LINK.


As far as we can tell, almost all crude oil (petroleum) is biogenic, and specifically comes from marine organisms. That's the only theory that is supported by the geological record, by the thermodynamics, and by what we know of the biology and the chemistry.

That's not to exclude the possibility of abiogenic petroleum: indeed, we know that abiogenic liquid hydrocarbons are possible, because we can synthesise them ourselves. So finding hydrocarbons that cannot be biogenic does not show that most fossil fuels are abiogenic: it merely shows that some abiogenic hydrocarbons exist.

However, the quack theory, popular in Soviet Russia and with other fringe pseudo-scientists, is that almost all oil discovered in the ground comes from abiogenic sources. Geoff Glasby looked at how the pseudo-science came about, in his article Abiogenic Origin of Hydrocarbons: An Historical Overview (Resource Geology, vol. 56, no. 1, 85–98, 2006) DOI:10.1111/j.1751-3928.2006.tb00271.x


Are there significant amounts of rare earth elements on Iceland?

The simple answer is no.
There are not any significant rare earth elements (REE) deposits in Iceland. This question: What are rare earths and why do they cluster near alkaline magmatism? gives a list of possible formation mechanisms.
Basically, to form a magmatic deposit of rare earth elements, simple magmatic activity is not enough. It would have to be magmatic activity related to one of two processes (or both):

Magma formed due to very low degree of mantle melting. REE are incompatible elements, meaning that they concentrate into the liquid during melting. If the mantle melts to a very low degree (let's say less than 1%), REEs are concentrated in it. Once the melting proceeds, the REE-rich liquid is diluted by further REE-poor melt. Rocks that form in this process are, or example, carbonatites and alkaline magmas. They do not exist in Iceland (and if they do, very scarce).
Magma that has evolved and differentiated. Let's say we take the REE-poor magma from 1. Now it starts crystallising. Remember that REE are incompatible and will stay in the liquid. So the residual melt eventually gets enriched in the REE. Think salt water being evaporated - the salt remains inside the water making it more saline. Pegmatite is one type of rock that forms in this process. Similarly, it does not occur in Iceland.


What does the absence of passive margins between 1740-1600 million years ago tell us about the tectonic environment at that time?

Good paper you reference there.  I think you are starting to answer some of your question by noting that Bradley associates the absence in passive margins with the Nuna supercontinent.  All "rifting" / spreading is taking place in the oceans - pretty much a requirement for supercontinents,  and in this case all continental margins (or at least for those with surviving geological record) were destructive margins.  Over time the duration of passive margins has changed.  For more recent supercontinents you mention, the shorter cycle of a passive margin may have made it very unlikely that tectonic events could cause a simultaneous gap in all passive margins.

As Bradley points out in his conclusions, tectonic activity when Nuna was around may have been globally more sluggish that today, or during the time of Rodinia and Pangea. It may also tie in with the formation of some mineral deposits.  For example, there is a peak in porphyry deposits at about this time.  Now taking into account that older porphyry deposits are less like to have survived (lost through erosion, buried or consumed in later tectonics) the peak at this time may reflect that it was a particularly good porphyry generation time for so many to have survived.  Porphyries do like convergent margins and there would have been lots of those.


How does the energy of tornadic winds compare to floodwaters?

The force exerted by a moving fluid (gas or liquid) per unit area is
proportional to its density $D$ and to the square of its velocity $V^2$.
The power delivered by a moving fluid (gas or liquid) per unit area
is proportional to its density $D$ and to the cube of its velocity $V^3$.

Water is about $800$ times as dense as air.
So water moving at $(\frac{1}{800})^{1/2}$ or about $\frac{1}{28}$ as fast as air exerts the same force per unit area,
and water moving at $(\frac{1}{800})^{1/3}$ or about $\frac{1}{9}$ as fast as air delivers the same power per unit area.

Or in other words air must move $800^{1/2}$ or about $28$ times as fast as water to exert the same force per unit area, and $800^{1/3}$ or about $9$ times as fast to deliver the same power per unit area.

Thus water moving at $6$ mph exerts the same force per unit area as air moving at about $170$ mph (a $170$ mph wind), and delivers the same power per unit area as air moving at about $55$ mph (a $55$ mph wind).

So it is not the power of 6 mph water that equals that of an EF4 (not EF5) tornado, but the force.
$6$ mph water has the same power as a 55 mph whole gale.


It's been identified by a paleoichnologist as most probably a new species of Paleodictyon.


How does remote sensing of ocean currents work?

I'm not familiar with land-based methods, but for global measurements, one method is to use satellite altimetry (I'm more familiar with the geodesy side, but many of the same satellites are used).  I think many of the current methods interpolate global or regional currents from a sparse network of buoys.  As more radar satellites are launched, however, satellite measurements of sea surface currents will become more common.

Global-scale satellite-based radar altimetry measures the average elevation of the ocean's surface over a few kilometers (the exact amount depends on the wavelength of the radar band being used).  Over this distance, waves cancel out, so the measurement is accurate to within a few centimeters.  (This is aided by using the motion of the satellite to enhance the image, referred to as Synthetic Aperture Radar (SAR).)

Surface currents in the ocean are directly related to the slope of the ocean's surface. (Again, at the scales we're working with, wind-formed waves cancel out.)

Once you have an accurate snapshot of the elevation of the ocean, you can calculate the direction and magnitude of the surface currents.  (Note that this is only the surface currents! Deep ocean currents are different matter altogether.)

This is also how we coarsely map the ocean floor from space.  (For example, Sandwell & Smith's extensive work: http://topex.ucsd.edu/WWW_html/mar_topo.html)

The average elevation of the ocean's surface with respect to center of the Earth follows the geoid (by definition).

Seamounts on the ocean floor cause a preturbation in the geoid above them.  Water effectively "bunches up" around seamounts (or rather, the surface of gravitational equipotential "bunches up" above the seamount).

By repeatedly measuring the oceans surface (over several years) we can remove the effect of surface currents and get an accurate picture of what the geoid looks like over the ocean.  You can then use this to predict water depths over the oceans on a spatial scale of ~1 kilometer.

In fact, to calculate surface currents, you need this information to begin with.  The surface currents are calculated as deviations from this measurement of the geoid.


You might try the RockFab package. I am not a structural geologist but I use other R packages for geological endevours.

Documentation.


Is there conclusive evidence for the Antarctic Circumpolar Current developing after the glaciation of Antarctica?

Lyle et al. (2007), prior to the paper you mention, also came up with this idea that the ACC initiated with its modern setting (i. e. with strong currents and mixing throughout the water column)  during the Late Oligocene (ca. 25 Ma), so roughly 10 Myr after the Eocene-Oligocene when the antarctic glaciation is thought to have occurred. Their evidence is based on sedimentology, specifically the presence of erosional structure associated with deep current flow. They however don't discard in this paper the idea that a surface ACC existed prior to this.

The original idea (Kennett 1977) according to which the ACC started near the Eocene-Oligocene transition was based on the observation of biogenic sedimentary facies pattern (classically siliceous south of the ACC and carbonaceous north) coupled with the observation of the opening of the Drake Passage around that time. Later, observations of the establishment of an endemic antarctic planktonic fauna during the latest Eocene (e. g. Lazarus & Caulet 1993, Lazarus et al. 2008) and measurement of Nd isotopes (Scher & Martin, 2006) at Agulhas Ridge (i. e. south of Africa) that coincides with Pacific waters values strengthened that hypothesis.

However, the idea that the antarctic glaciation was a consequence of the setting of the ACC has been somewhat challenged (De Conto & Pollard, 2003, and later Barker & Thomas, 2004) based mainly on numerical modeling, as they show that, although a developed ACC would have participated in the cooling triggering the glaciation, it is not a necessary condition for it: the glaciation could have entirely been caused by the observed drop of atmospheric $p_\mathrm{CO_2}$, even without a developed ACC.
Additionally, some of the evidences for an early setting of the ACC (namely the facies change argument) could very well be a consequence of the glaciation rather than the consequence of the ACC (Barker & Thomas, 2004).

So, as far as I see, we are at a stand-off, where we have arguments in favor of a late settling of the ACC (mostly sedimentary and tectonic arguments) and at the same time arguments in favor of an early settling (in particular paleontological and geochemical arguments) and no real reason to discard any.

References:
Barker & Thomas, 2004. Origin, signature and palaeoclimatic influence of the Antarctic Circumpolar Current. Earth-Science Reviews, 66: 143-162.
De Conto, R.M., Pollard, D., 2003. Rapid Cenozoic glaciation of Antarctica induced by declining atmospheric $\mathrm{CO_2}$. Nature 421, 245 – 249.
Kennett, J.P., 1977. Cenozoic evolution of Antarctic glaciation, the circum-Antarctic Ocean, and their impact on global paleoclimate. Journal of Geophysical Research, 82: 3843–3860.
Lazarus, D. B. & J.-P. Caulet, 1993. Cenozoic Southern Ocean reconstructions from sedimentologic, radiolarian and other microfossil data. In J. P. Kennett and D. A. Warnke (Eds), The Antarctic Paleoenvironment: a perspective on global change. Antarctic Research Series, 60: 145-174.
Lazarus, D. B. et al., 2008. Patterns of opal and radiolarian change in the Antarctic mid-Paleogene: clues to the origin of the Southern Ocean. Micropaleontology, 54(1): 41-48.
Lyle et al., 2007. Late Oligocene initiation of the Antarctic Circumpolar Current: Evidence from the South Pacific. Geology, 35: 691-694.
Scher, H. D. & Martin, E. E.,  2006. Timing and Climatic Consequences of the Opening of Drake Passage. Science, 312: 428-430.


This a type of arcus cloud called a shelf cloud and is caused by moist air rising over cool thunderstorm outflow.  These clouds can look quite dramatic but do not pose any threats themselves.  However, they can signal the presence of strong winds behind the gust front.
These clouds can often be associated with strong convection -- squall lines, supercells, etc.  These storms often have strong inflow coming from ahead of the storm supplying the storm with moisture.  The storm is producing rain-cooled air and this dense air wants to spread out along the ground.  If the outflow becomes too cool (relative) or the inflow weakens, the storm outflow can race ahead of the storm.  This will produce strong winds as the gust front surges ahead and if the inflow is moist enough it will produce a cloud as it rises up and over the cool outflow.  This cloud marking the gust front as it the rises up and over is a shelf cloud.
These definitions are taken from a NWS storm spotter glossary:

Arcus - A low, horizontal cloud formation associated with the leading edge of thunderstorm outflow (i.e., the gust front). Roll clouds and shelf clouds both are types of arcus clouds.
Shelf Cloud - A low, horizontal wedge-shaped arcus cloud, associated with a thunderstorm gust front (or occasionally with a cold front, even in the absence of thunderstorms). Unlike the roll cloud, the shelf cloud is attached to the base of the parent cloud above it (usually a thunderstorm). Rising cloud motion often can be seen in the leading (outer) part of the shelf cloud, while the underside often appears turbulent, boiling, and wind-torn.


Is there a name for a "moving meridian" corresponding to particular solar time?

This is better suited for English Language &Usage SE, but the word you're looking for is

Isochron

  an imaginary line or a line on a chart connecting points at which an event occurs simultaneously or which represents the same time or time difference

(Source: Merriam-Webster)

Isochrons are typically used in diagrams rather than maps, for techniques like rock dating, where correlating things by time is more important.

But cartographers are used to putting all types of isarithms on maps, and would understand what an isochron was meant on a map.

The trick is to define "same time" as "same solar time", giving you the "moving meridian" you're looking for.

You could contrive a more specific term like isoheliochron but it hardly seems worth the effort, because they're pretty boring on a map.


In my field of oceanography, objective analysis (OA) is often taken as a synonym of optimal interpolation (OI). (e.g. Emery & Thomson, Section 4.2; and in many lectures).

The same method is also referred to as objective mapping or Gauss-Markov smoothing. In this case OA is a least squared interpolation where the estimate is unbiased and the expected error is a minimum in the least squares sense.

In many other cases, objective analysis is taken to be a specific type of optimal interpolation. A good example is the group from University of Liege. In this case OI includes other methods like kriging, successive corrections or the Cressman method.

In my case, I tend to follow the nomenclature and suggestions by Ide et al. (1997).


How do we know graptolites were pelagic?

Basically, we know they were likely pelagic creatures because we find their fossils at essentially all water depths.

If they were benthic creatures, we'd expect their fossils to be limited to a set range of paleo water depths.  It's unlikely that a single benthic (i.e. living on the seabed) marine organism could live in both shallow water and ultra-deep water.

However, for pelagic (i.e. floating or free-swimming) creatures, we'd expect to find their fossils at a huge range of paleo water depths because they live in the water column and don't care where the bottom is.


No, no such changes have been observed. Laclare et al. (1996) summarize various published solar diameter data from observations made between 1970 and 1995. Here's Figure 6 from their paper.

As you can see (and as Laclare et al. point out), solar semi-diameter has shown no significant variation during the measurement periods. Given their deviation from the other data sets, the Wittmann data seem rather suspect, but even they show absolutely no change between the 1972 and 1981 data points. In short, none of these data are consistent with the notion that solar diameter changed in 1979.

References

Laclare, F., Delmas, C., Coin, J. P., & Irbah, A. (1996). Measurements and variations of the solar diameter. Solar Physics, 166(2), 211-229.


Land that has been heavily disturbed by humans in most developed countries, such as urban and rural regions will have been surveyed for topographical & sub-division purposes.

Such data allows for a digital terrain model (DTM) to be created for such regions. When subsidence occurs, the subsided area can be resurveyed & compared to the original DTM to ascertain the amount of subsidence that has occurred.

Undisturbed or poorly surveyed regions become problematic. The subsidence area & the surrounding area can be surveyed, but then someone has to make a judgement call & decide what the original surface may have looked like to infer an estimate for the degree of subsidence.

The other way is to have satellites periodically measure surface elevations & then to do comparisons between each satellite measurement.

Radar could be used as the measuring system, but LIDAR (& this reference also) can produce more accurate results.


Looks like a sand dollar fossil.  Note the pentagonal shape in the middle.

Source: fossilera.com


What are the latest developments about global stilling?

It seems to be a thing of the past. Apparently around 2010 the 30 years calming trend reversed. Since then, wind speeds and wave heights are picking up quickly, possibly in a decadal variation pattern.
Young et. al. 2010 Global Trends in Wind Speed and Wave Height
Possible application for the planning of wind turbines:
Zhenzhong Zeng et.al. 2019 A reversal in global terrestrial stilling and its implications for wind energy production
From the abstract of the latter:

... we use wind data from in situ stations worldwide to show that the stilling reversed around 2010 and that global wind speeds over land have recovered. We illustrate that decadal-scale variations of near-surface wind are probably determined by internal decadal ocean–atmosphere oscillations, rather than by vegetation growth and/or urbanization as hypothesized previously. ...

Similar observations of an increasing trend over ocean surfaces, overlapping with the period of global stilling over land.
Ching Wei Zheng et.al. 2016 Global oceanic wind speed trends
Can only read the abstract of the latter. Would be interesting to investigate further the reason for the differing observation and modelling of sea- and land-wind speeds during the term.


What theories exist connecting volcano temperatures to eruption probabilities?

I have not heard of complete theories connecting volcano temperatures to eruption possibilities either. If you mean subsurface magma temperatures, it is uncommon for there to be direct observations / readings for a particular volcano. Fumarolic temperatures, on the other hand, are directly indicative of current volcanic activity and are much more easily measured (example). In addition, geochemical analysis of fumarolic gases can be related to eruption probability (example, example).

Even in models of magma ascent, temperature differences are not the main focus, but rather pressure differences are (example). This is directly related to g.z.'s comment that volatile content certainly can be a dominant eruptive trigger.


Is there a place where the sea floor descends into the mantle of the earth?

The subduction zones are more easily spotted by the phenomena they cause in the subsurface than their features on the surface. I found this schematic image which shows almost all the features, from https://www.researchgate.net/publication/318684905_The_Nahuel_Niyeu_basin_A_Cambrian_forearc_basin_in_the_eastern_North_Patagonian_Massif :

So what you see is the thin black plate subducting under the grey continental rocks. There are two features that it causes in an indirect way.

The first of those is the forearc basin, which is a sometimes present region with thrust faults in the direction of the subduction point. Thus, there is a local basin with a lot of space for sedimentation.
The volcanism, then, is the most obvious and always-present feature. All the chemicals that the ocean floor brings into the Earth at relatively low temperature create a 'melt' that can eventually reach the Earth's surface.

The reason why we don't see the actual subduction happening with our own eyes is because of the formation of the 'accretionary prism'. This is the triangle-shaped feature on the figure. It consists of sediment that is held on the interface between the moving oceanic plate and the stationary continental plate. It's a bit like a bulldozer. Hence, the real subduction action is covered by kilometers of piled up sediment! The deepest natural trench in the world, the Mariana Trench, is only about 11 km deep, while the continental plate is probably at least ~40 km deep. Hence, we don't really see the actual subduction in action...

If you have a shripwreck hulk and place it in the Mariana trench, it will get covered with sediment with a speed of ~0.02cm/year, so assuming your ship is about 30 meters high it will take 150 000 years before it is covered and can become part of the accretionary prism. Then it has to be dragged into the Earth somehow. The Nazca plate moves at ~5 cm/year, so it'll be moved by 7.5 kilometers forward. As I wrote, it'll have to subduct at least 30 more kilometers before it's below any continental plate, which would take at least 600 000 years at the speed of the plate motion, and assuming that it somehow moves at the same speed as the crust rather than getting bulldozered into the accretionary prism. In other words, it would probably take much much longer in practice before it reached far enough down. As said, that means that in the meantime your space ship will have been chemically weathered and mechanically deformed (by the enormous mass of sediments), and won't really be recognizable as a space ship anymore!


Does temperature affect partial pressure of gas dissolved in water?

have always been under the impression that if a gas is in equilibrium between its gaseous and aqueous forms, that it will always have the same partial pressure in the air as in the water. For example, both air and air saturated seawater have a pO2 of 21.227 kPa (101.325 kPa x 20.95%).

That's a very bad impression, and your example is just not the case. Oxygen solubility in water at 0°C at one atmosphere of pressure is 14.6 mg/liter in fresh water, 11.2 mg/liter in salt water (35 g/kg salt). Those values correspond to 1036 pascals and 794 pascals, respectively.

Oxygen solubility in water is highly temperature and pressure dependent. Like most (but definitely not all) gases, oxygen solubility in water is greatest at 0°C.

Oxygen solubility comes very close to following Henry's law for typical pressures. Henry's law says that "at a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid." The constant of proportionality is not constant. It instead is a function of temperature and the nature of the liquid.


What does the notation "kg kg-1" for units mean for specific humidity

Yes, the unit is kilogram per kilogram, but it means kilogram of water (moisture) per kilogram of air.


What are these river/canyon-like carvings in the ocean?

The carvings are submarine canyons, a part of the continental slope leading from the continental shelf to the continental rise and ultimately the Abyssal plains. They are a product of :

erosion through currents and
slumping of the continental shelf

Like other erosive or slumping effects, they can be self-reinforcing, leading to canyon-like structures. The highlighted canyon here is the Gollum Channel system, seen here.


What precursor geological activity occurred prior to the Parícutin Volcano eruption in 1943?

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

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

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

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

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

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

References

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

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

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


How to properly setup a domain in NWP model (WRF) according to meteorological input data

A good rule of thumb for down-scaling with WRF is not to interpolate down more than 3 or 4 times; with 3 being the standard recommendation. So while 18 km is probably overkill for an outer domain (this is a personal opinion, there are some operational models like HWRF that start at 18km), 2km would definitely be too fine for a parent domain. The main reason for this is the boundary conditions: your wrfbdy_d01 file is interpolated from the original data down to your model's resolution, so for a 2km domain you will be constantly having very low resolution features imposed upon your boundaries, which will cause fairly unphysical conditions at the boundaries throughout your forecast period. By having a wider, lower-resolution "buffer" domain between you and the outer boundary conditions you avoid unphysical artifacts entering your domain.

There are 5 overlap gridpoints at the edge of each domain, so your inner domain should be at least 5 (outer) gridpoints away from the outer domain.


Does the size of Earth increase due to volcanism?

This is actually a more complicated question than it seems on the surface (no pun intended). The short answer is that the volume vacated by the magma is eventually refilled by the very tectonic processes that filled it in the first place. Crust is subducted, molten, and then rises to fill magma chambers. The process goes on and on. In some cases the plate that was being subducted eventually disappears (this will happen to the Juan de Fuca plate in a few million years), and the volcanoes associated with become extinct, not dormant but extinct. But generally speaking, volcanism is an ongoing process; the Earth is constantly recycling crustal material


How much does the gravitational and magnetic fields of a planet effect the chemistry in it?

How would the chemical reactions seen everyday on earth be different if the strengths of these fields were different?

Depends. If you're just talking about higher $g$ (i.e $g>9.8\ \rm{m/s}^2$) but the same atmospheric pressure, than not much will change on the surface of the earth.
If the atmospheric pressure changes, there could be changes to chemical reactions. There are several factors controlling chemical reactions. One being, obviously, the identity of the reactants. The other one is temperature. But also important is pressure. Because pressure on the surface of the earth is always 1 atm, no one really thinks or cares about pressure. No one, until it changes. That said, for any substantial change in chemistry, pressure has to change quite a lot, which would make earth uninhabitable for humans, so there would be no one to see that chemistry changed.


What's a reasonable flow rate/mass flux for a fumarole?

Surprisingly enough most of the figures I could find were actually about thermal output but back working the figures, and assuming I read the formulas properly (not guaranteed I'm afraid) it looks like 5-7 litres per second is the ballpark average gas flow based on fifty years worth of data from several fumarole fields in the central North Island of New Zealand. I have no idea how representative that figure would be of fields elsewhere.


Why has CO2 decreased in the history of the Earth?

The short answer is that most of the Earth's original allotment of CO2 got locked up in various carbonate minerals, largely calcite (limestone, marble, and chalk).  According to this article there is currently ~800 gigatons of carbon in the atmosphere today; there is ~39,000,000 gigatons of carbon locked up in calcite minerals. All that carbon was once in the atmosphere as CO2. Rainfall dissolved CO2 into H2CO3 (carbonic acid) which then reacted with calcium-containing minerals and then precipitated out in the world's oceans where they formed early calcite deposits.If not for this process the Earth's climate would not be too unlike Venus'.


What is the difference between the freezing level and 0C isotherm in NOAA's GFS?

Various processes affect the freezing point. Both CCN (cloud condensation nuclei) characteristics and drop size affect the freezing point.


Need help understanding rain rate formulas from drop sizes

The first equation does not match up with the units. But first things first... What you're calculating when you calculate rain rate is an accumulation rate, which is volume flux through a plane (mass flux divided by density) divided by the area of that plane. For this reason, it doesn't matter whether it is computed over a square meter or a square kilometer -- since volume flux is proportional to the area, it cancels out

Also it doesn't really matter whether $N(D)$ has units of $mm^{-1} m^{-3}$ or $cm^{-1} m^{-3}$, since that first unit cancels out in integration.

If the units are as you say they are in the first example, then the expression should read
$$R_1 = 10^{-6}\frac{\pi}{6} \int_0^\infty v(D)D^3N(D)dD$$
to get a result in $mm/s$.

Multiplying this by 3600 to get a result in $mm/hr$ yields the the second expression.


Where I can find high-res public domain images of Countries or Continents on the web

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.


Is it dangerous to live in Seattle due to the earthquakes?

Yes. Earthquakes are Dangerous

No. Because big earthquakes happen so infrequently (~300 years in Seattle's case) that one shouldn't really worry about it. Engineers design buildings to withstand large earthquakes. Of course there is the possibility of failure, but generally the US is very good about their infrastructure. Seattle is not like Oklahoma, where they are completely unprepared for earthquakes. I lived in Los Angeles in 18 years, and while my time there was during the Northridge 1994 earthquake, most of the damage was to the buildings (which were insured) and not to the people. Still there is some risk, but I think the risk of driving in Seattle is probably riskier than living in Seattle for 50 years of earthquakes.


What could cause a turn from global warming to global cooling?

Pleistocene's climate variations are well correlated with Milhankovitch Cycles.

  "Variations in eccentricity, axial tilt, and precession of the Earth's
  orbit resulted in cyclical variation in the solar radiation reaching
  the Earth, and that this orbital forcing strongly influenced climatic
  patterns on Earth."

  Source: Milhankovitch Cycles, Wikipedia

At this graph you can see eccentricity explains major Oxygen $δ18$ variations at Pleistocene oceans. $δ18$ is a known proxy for temperature.

  Source: euanmearns.com

The minor peaks are Earth's internal forces reaction to changes on solar radiation. Earth has subsystems that store and interchange the energy received from the Sun, resulting oscillatory climate tendencies.

Aswell as the atmospere and the hydrosphere, cryosphere has internal forces as a subsystem; and oscillatory events (development of ice-break of ice). One example of punctual changes due to cryosphere internal forces dynamics are Heinrich Events, that can influence climate at minor scale than eccentricity does and be correlated with some of the peaks your graph shows.


Wildfire acreage, two dimenional or three?

The same issue arises when land is bought and sold. The area used is the flat area from a plan. Slope is not considered because it would require at lot of data because the rate of change of topography and slopes is never uniform. Also the calculations to determine the true area can be convoluted if the change in topography is complex.


Where can I find the record for the heaviest single-day rainfall ever recorded on any date at a specific location?

Sounds like your question, like most questions about historical data, might be a little challenging to find the right source, as it often is around the world.

But seeing you said Atlanta brightened my eyes!

For if one is seeking information for a US climate observation sites (most big cities, and a fairly reasonable web across the US... there's about 2-6 per Weather Service office), then there's a great source for historical data that, with a little looking around, allows you to fairly quickly answer quite a lot of interesting questions about your area once you get used to doing it... the NowData portal on your local National Weather Service Office's website.  To find this:

Go to the National Weather Service.
Click on your local area (which will take you to your local NWS Office webpage)
Scan across the middle of the page about halfway up to find the climate and past weather drop down and you should come across the NowData link (for this one I had to click more in the menu)

Disappointingly tough to navigate to the NowData hub, but you only really need to find it approximately once, and then you're set!

To speed you along: this is the direct link for the Atlanta (Peachtree City) area.

Then, once you get to the NowData page, you want:

The Atlanta area as the selected location (that will combine the past and current official Atlanta observation sites together to go back as far as possible for the official Atlanta observation)
For product, click the calendar day summaries radio button
The year range should likely be good... you want por- (por = period of record, meaning back to the very start of record keeping)
Variable = Precipitation
Summary = Daily Maximum

And viola, click Go, and you'll have it.  No, it's not a single list.  In some ways, to some, it may be better, it's a page of the maximum precipitation values every day of the year.  (Which allows you to see other things that might pique interest... such that [as is common in precipitation data due to such wild variability], the days calendar days on which Atlanta has never received an inch of rain are: February 29, April 21, May 10, May 12, September 9, September 12?

Anyways, it's a bunch of numbers... but the extra positive is that the maximums for each month are highlight red.  So just search through those quickly, you should find that the maximum 24-hour recorded rainfall in Atlanta history is:

1. 7.36" on March 29, 1886

Second (assuming there was no additional great storm on a different March 29th!) was much more recent:

2. 6.68" on October 4, 1995

You may well be able to dig around the climate category on that Peachtree City National Weather Service page and find more information on the major storms including those, and a better, simpler list.  But if not, at least the NowData offers the chance to reliably get answers to many questions like yours.

I know, it's definitely not all the most intuitive.  At least it's consistent.  And, especially if you have some rudimentary spreadsheet experience, it can be made to tell you what you need rather quickly (in 15 years of meteorology, I still regularly use it myself.)  If somebody has a very reliable, comprehensive source for historical data that is fairly straightforward to the typical user, I'd be absolutely right at the front of the line to congratulate them.

(And it is indeed a real pity, that in an era where the big concern is supposed to be changing climate, it still is fairly abstruse and convoluted to get great comprehensive climate information in an intuitive way from an official source)

But hopefully, while it's not absolutely beautiful in method, it not only answered your question, but given you and others the tool to answer the same question and quite a few others on temperature\precipitation climate\history for many other cities around the country!


If lava flows back into the ground, would it be called magma?

Lava is per definition the molten material on the surface or a hardened rock thereof. Lava is expelled from a volcano or fissure. There is a rich vocabulary to describe the composition, formation and processes of lava.

Magma is a melt within the earth. Magma is formed when material reach a temperature for melting or partial melting, e.g. in a magma chamber. Complex high temperature chemistry is used to describe how solid material melts to magma and how it recrystallizes into igneous rocks as a response to temperature, pressure and changed composition.

Magma can originate from any kind of material. The definitions doesn't refer to the composition or origin of the material, but the manifestation. Magma can be melted or partially melted crust, also old volcanic crust, so if old lava somehow re-enters a magma chamber it will be magma. When magma is erupted, it is lava.

There is often some confusion, even among professional geologists, about many of the terms we are using. Some terms describes a process and other describes an object. Sometimes we say Upper Jurassic, sometimes Late Jurassic depending on the context. Some terms are historical and some are modern... There are often overlaps.

As for any language, it's good to use a broad vocabulary and adopt to the jargon, but most important is to communicate the ideas and observations as clear as possible.


What modelling approaches are used to predict the aurora?

One model is the OVATION auroral precipitation model.

OVATION stands for Oval  Variation,  Assessment,  Tracking,  Intensity, and  Online  Nowcasting.

The NOAA Space Weather Prediction Center uses the OVATION Prime model for their 30-minute aurora forecast. They use a modified version of the model for their 3-day forecast. It was devised by Newell et al. (2010) at Johns Hopkins University.

You can read all about it in Machol et al. (2013). The paper is open access and contains several equations and a description of the method. They explain:

  The OVATION Prime model is derived from electron and proton
  flux measurements from the SSJ4 detectors on the DMSP satellites.

SSJ4 sensors, according to one source:

  [...consist] of an array of four cylindrical, curved plate, electrostatic analyzers configured into two pairs; one pair each to measure electrons and ions. Each pair covers the energy range from 30 eV to 30 keV in 20 channels spaced at equal intervals in energy on a logarithmic scale.

References

Machol, J. L., J. C. Green, R. J. Redmon, R. A. Viereck, and P. T. Newell (2012), Evaluation of OVATION Prime as a forecast model for visible aurorae, Space Weather, 10, S03005, doi:10.1029/2011SW000746.

Newell, P. T., T. Sotirelis, and S. Wing (2010a), Seasonal variations in diffuse, monoenergetic, and broadband aurora, J. Geophys. Res., 115, A03216, doi:10.1029/2009JA014805.


Why is diabase/dolerite erosion resistant?

Diabase is indeed relatively erosion resistant. One of the reasons is grain size.

Consider the two other chemical equivalent of diabase: gabbro (coarse-grained) and basalt (glassy and fine-grained), which should potentially be similarly erosion resistant. This is not the case. Both gabbro and basalt erode very easily.

Coarse-grained rocks, in general, erode easily. The large grain size means it is relatively easy to dislodge individual grains out of the rock. You don't need a lot of water, for instance, to percolate between the not-many grain boundaries and release them. To make it worse, gabbros are full of minerals that are easily erodable such as plagioclase and olivine.

On the other hand, basalts also tend to weather easily. Having cooled fast, they are usually glassy which tends to crack during cooling. Glass is general is less resistant to chemical alteration than minerals, under similar conditions. Basalts also contain gas bubbles, which cause weakness spots in which the rock can break, leading to preferred weathering.

Diabase is fine grained, and contains no glass. It does not suffer from these two conditions. It is composed of very fine interlocking crystals that are very hard to dislodge, and is not penetrable by fluids.

That said, remember that it is all relative. A diabase will still weather faster than even the worst type of granite.


The quantities of oil in a deposit are listed under two categories: resources and reserves.
Resources are deposits that could be converted to reserves if economic factors, prices and costs, were favorable.
Reserves are deposits that can be extracted for a profit.
What makes a deposit profitable involves many things:

The size of the deposit
The quality of the deposit - the type of hydrocarbons in the deposit,
is it lighter fractions of oil or heavier or a mixture of the two. It
also depends on the amount of undesirable contaminants in the oil
such as sulfur.
The depth of the deposit
Ease or difficulty in accessing the deposit
The flow rate achievable from the deposit: the number of barrels of
oil per day that can be extracted.
How much gas is associated with the deposit and the type of gas
Ease of getting the oil to a refinery
How much of the total oil in the ground can eventually be extracted.

The amount of oil that can be extracted is heavily reliant on the technology used to extract it. With the introduction and use of technologies not previously available more oil might be able to be extracted from the deposit, or oil from deposits not previous considered for extraction could be converted to reserve status and become available to be extracted. When this happens the hydrocarbon resources have become extended.
Similarly, new technology might make oil in different types of deposits capable of being extracted. This is what happened with oil shale deposits when fracking was developing. Until then oil shale deposit were largely untouched.
By being able to extract oil from such new sources also extends the hydrocarbon resource.


downloading ERA5 netCDF daily data for a decade, how to restrict location to reduce data size?

There are two ways to get this done:

1- you can select the specific domain of interest when downloading the files. This is highly preferred when you have to download a large number of variables and years. ERA5 netCDF are offered in two different formats: either at hourly time steps, or at monthly averages (see this). If you need a sub-monthly time steps the global files for many variables for long time periods are extremely heavy in terms of disk space. You could set up a python script to download the data selecting only the domain by following a procedure like the one suggested in this nice post by Reto Stauffer (of course there are other ways to do this).

2- you can download the global netCDF of the variable and year under consideration ad use a software to extract your domain of interest.
One of the most efficient systems to do that is using the Climate Data Operator CDO. you could use the sellonlatbox with a command like

cdo sellonlatbox,LON1,LON2,LAT1,LAT2 Input_file_Name.nc Output_file_Name.nc

Or you could use R, as for your case, doing something like:

library(raster)
library(rgdal)

#load your area of interest
setwd("path_domain_shapefile")
domain_shp<-readOGR("shapefile.shp")

#read netCDF
setwd("path_to_ERA5_files_folder")
pr_data<-stack("ERA5_file.nc")

#extract the data for your area of interest
pr_data_domain<-extract(pr_data, domain_shp)

#then you can transform this in a data frame and write it as a csv

As reference for basic operations with spatial data in R, I would suggest this introduction guide.

Hope this helps.