There are many models that estimate orbital parameters at long timescales. All of them rely in rather complicated formulas that account for the perturbations generated by other planets, the Moon, and many other factors. Some of the models even consider relativistic effects as described in this answer.

An orbital solution that I often see cited and used in papers dealing with climatic forcing is LA93, computed by Laskar et al. (1993) and described in the paper Orbital, precessional, and insolation quantities for the Earth from -20 MYR to +10 MYR. However, more accurate solutions are available by now, like LA2004 and more notably LA2010. I'll describe below how to download output data and codes for each of these solutions.

For LA93, the codes (in fortran) and outputs of that model are available at the VizieR catalogue, where you can query the model output, or just go into this FTP folder and download the files for the code and long tables with the model outputs every one thousand years.

If by "the three Milankovitch factors" you mean Obliquity, Eccentricity, and   Precession index (Eccentricity $\times$ sin(longitude of perihelion)). That data is ready to download and use in these two files:

CLIVAR0N.ASC (-20Myr to 0Myr)
CLIVAR0P.ASC (0Myr to +10Myr)

The byte-per-byte description of these files as described in the README is

--------------------------------------------------------------------------------
   Bytes Format  Units   Label     Explanations
--------------------------------------------------------------------------------
   4- 11  F8.0   1000yr  t         Time from J2000 in 1000 years
  13- 31  D19.12 ---     e         Eccentricity
  33- 51  D19.12 rad     eps       obliquity (radians)
  53- 71  D19.12 ---     CP        e * sin(longitude of perihelion
                                           from moving equinox)
--------------------------------------------------------------------------------

With the code you can also compute common climatic proxies such as isolation at 65°N or any other latitude.

For LA2004 (-50 Myr to +20 Myr) the same research team implemented a very useful online calculator that allows to compute insolation quantities derived from the orbital and precessional quantities for any latitude of interest. It outputs the results in tabular form. The calculator interface looks like this so you get an idea of the available options.

The LA2010 solution is described in the paper La2010: a new orbital solution for the long-term motion of the Earth, and goes 250 Myr back in time. You can find similar data files and codes for this solution at the Astronomical Solutions for Earth Paleoclimates page. To my understanding, LA2010 represent the state-of-the-art solution for orbital parameters and it does include relativistic corrections as well.


How probable is is that earth magnetic field will change 180 degrees at once?

The magnetic north pole (and presumably the south pole) currently moves around 40km/year, although within a year it loops around, may travel much further than that forwards and backwards. Here is a map of the movement from the past century and a half (source)
:

However, during a magnetic reversal, the pole may move up to 10 times faster than that, over a period of less than 100 years. Here's a map showing the relative movements (the numbers are thousands of years ago (kya)) (source)

]

The reason for reversals aren't very well understood (according to the previous link), and I'm in no way an expert in the field, but just for some fun speculation, I would wonder whether reversals might be related to this phenomenon. Obviously a liquid outer core is going to operate differently from a screwdriver, but the two systems both appear to be exhibiting a bistable rotation while floating in space.


Does muscovite occur as a contact metamorphism mineral?

Yes, wikipedia page for muscovite tells:

Muscovite is the most common mica, found in granites, pegmatites,
gneisses, and schists, and as a contact metamorphic rock or as a
secondary mineral resulting from the alteration of topaz, feldspar,
kyanite, etc.
Source: Muscovite, Wikipedia.

As always, you need to corroborate wikipedia is correct, but there are several papers that talk about muscovite on contact metamorphism environments, you can do your own search on a scientifical database.
Here is an example about a paper that deals with muscovite found on contact aureole of Duluth Complex, Minnesota.
So yes it is a mineral phase formed in that conditions of increased temperature due to an intrusion.
For you specific question about contact metadacites, yes too, they can develop muscovite as shown in this book about US geology.


Can we extrapolate wind speed data to higher altitudes?

Yes, but it may not be valid. The extrapolation will be valid for about 0.1 * PBL Height using the Log-Wind Profile

You will need:

PBL Height.
A second Wind speed (within 0.1*PBL Height)
Surface Sensible Heat Flux
Surface Latent Heat Flux
Potential Temperature

You can use the last three variables to calculate the Monin-Obukhov Length (MOL). Then use the MOL to calculate $\psi$:

If L>0 $\psi=\frac{z}{L}$

If L=0 $\psi=0$

If L<0 $\psi=2\ln(\frac{1+x}{2})+\ln(\frac{1+x^2}{2})-2\tan^{-1}(x)+\frac{\pi}{2}$

where $x=(1-15\frac{z}{L})^{\frac{1}{4}}$

Now that you have $\psi$, you can derive the friction velocity and surface roughness length using the log-wind profile  and $\psi(\frac{z}{L})$. Once you have those two, you can extrapolate wind speed 600 meters up, provided the surface layer is that high.


How do you stop the Australian wildfires?

As of 7 January 2020, the total area burnt by the fires in the whole of Australia is 8.4 million hectares (21 million acres; 84,000 square kilometres; 32,000 square miles. That is equivalent in area to the nations of Austria or the United Arab Emirates. Greater in area than the Czech Republic, Ireland or Sri Lanka.
The vast majority of that has been on the eastern side of the country, in New South Wales (49,000 sq km) and Victoria (12,000 sq km). In Western Australia, the area has been 15,000 sq km and has forced the closure of the southern road between east and west twice.
With many fires burning in many areas the only course of action is to let the fires burn out by themselves. The efforts of fire fighting crews is to mainly protect areas from being burnt: properties and ecological regions of significance, such as the region containing Wollemi pines and other forested areas.
Dumping sand, as you inquire about, has problems: from where to source the sand, the amount of sand required, how to dump the sand, will the dumped sand have a negative environmental impact afterwards.
The fire fighting methods currently use in Australia are the same as with fire fighting practices for bush fires (wild fires) elsewhere. Fire are left to burn themselves out. The fringes of fires will be doused with water, either by ground crews and water trucks or via aerial bombardment, with water bombers (fixed winged aircraft or helicopters). Beating fire out is also used. Aerial bombardment will also include the used of fire retarding chemicals.
To prevent fires from spreading, firebreaks are also made, where large areas of ground are cleared of flammable material to prevent them from being ignited by ember attacks. This can also include the use of back burning, by fire crews, where forest is deliberately set alight by fire crews. This is only done when considered necessary and when weather conditions are favorable - wind directions and strength, humidity and temperatures.
The trouble with bush fires in Australia is eucalyptus is a significant species of Australian forests.  Eucalyptus requires fire to regenerate. They also shed large quantities of leaves and bark that accumulate on forest floors. A controversial method of minimizing bush fires has been to burn forest deliberately in cooler periods, under more controlled conditions, to reduce the fuel load during the main summer fire season.
By not letting the fires burn themselves out, the unburnt leaf and bark litter on the forest floors will remain and accumulate presenting another fire problem for the future.
Australia will always burn, it's the nature of its forests. Bush fires are an expected, but unwelcome part of summer in Australia. What Australia needs is better forest fire management strategies.

Edit 28 July 2020
Recent information about the Gosper's Mountain mega blaze that burnt more than one million hectares.
Anatomy of a 'mega blaze' - text and short videos of about the fire, from ignition by lightening strike, advance, merger with three other fires and how it was fought.
Gosper's Hill 'mega blaze', a 13 minute long video.


How does the subsurface earth temperature vary around the world?

The subsurface temperature will vary due to the soil type: sand, clay, loam, silt and the degree of saturation of the soil, soil thickness, the thermal conductivity of the soil, the surface temperature (time of the year) and the albedo of the surface.

Temperature changes within soil become less variable with depth.

So far I have only found information for two regions: the US-Virgina and Cyprus. Following is a series of curves for the US. A similar diagram is available for Cyprus, but its locked in a pdf file.

In Cyprus, the soil temperature at 3 m depth varies between 18 °C and 20 °C. In the US, at a depth of 12 feet (3.6 m) the temperature varies between 60 °F and 65 °F (15.5 °C and 18.3 °C).

These results are similar, but it needs to be noted both locations are in temperate climate zones. The latitudinal extent of Virginia is between 36.5° and 39.5° North and Cyprus is 35° North.

From research undertaken in Australia, the temperature at depth in a soil is also dependent on the air temperature and hence the latitude. At a depth of 1 m the soil temperature is 35 °C at latitude 10° South and 12 °C at latitude 45° South. There will be a corresponding difference at 5 to 10 m depth.

The British Geological Survey states:

  About half of the solar radiation received by the Earth is absorbed at the surface. As a result, the ground temperature shows seasonal fluctuations to depths of about 15 m where the temperature is approximately equal to the mean annual air temperature(8 - 11° C in the UK). Below this the ground temperature increases at, on average, 2.6 °C per 100 m due to heat flowing from the interior of the Earth. Mean temperatures at 100 m depth in the UK vary between about 7 - 15°C.


The white one is milky quartz, the yellowish/brownish one could be some variation of quartz or quartzite, too.

Further information about quartz and milky quartz can be found here


Do ocean level rise estimates account for mantle elasticity and plate mass changes?

Sea level rise estimates use changes in relative mean sea level. The definition being:

  Relative sea level is the sea level related to the level of the continental crust. Relative sea level changes can thus be caused by absolute changes of the sea level and/or by absolute movements of the continental crust.

In general, Mean Sea Level means the 'water level when it is still' (without waves). MSL is averaged over a determined period of time, such as a month or a year and it is measured relative to a fixed mark on the land (benchmark).

As MSL is measured relative to land, it can change due to changes in water volume or due to land movements. That is why we usually refer to it as 'relative sea level'.

Long-term changes of sea level are called "secular" changes and include isostatic changes. The main reason for isostatic changes at a global scale is the Glacial Isostatic Adjustment (GIA).

The body of scientific work related to the contributions by different factors is extensive. For instance, I like Cazenave & Nerem, 2004. Also, there is a lot of information about the relative contributions of each.

 Source: JPL-NASA

There is a lot more information about the regional distribution of sea level rise in: How will sea level rise be distributed across the globe?

Also, here is a good simple explanation of the factors affecting sea level.


Migration Routes for Animals from Asia to America

The jaguar is a close relative of the Asiatic leopard and must have had a common ancestor within the last 5 million years. The South American tapir is obviously closely related to the Malayan tapir and must also have had a common ancestor within he last 5 million years.

While the first statement is more or less correct, the latter is not. The Asian and American branches of the tapirs split about 25 million years ago.

Regarding migration routes, felines have migrated back and forth between Asia and North America many times in the last eight million years or so. The ancestors of Tapirs apparently migrated back and forth between North America and Europe before 25 million years ago, when the climate was much warmer and the continents had slightly different shapes.

  ... is there a possibility that when Africa and Amazonia were closer together, immigration from Africa could have taken place?

Regarding South America, there were very few placental mammals in South America until about 3 million years ago, when the Isthmus of Panama formed. The age of the Isthmus is debated. The sudden appearance of placental mammal fossils about 2.7 million years ago in South America, including jaguars and tapirs, is not. South America's jaguars and tapirs migrated to South America via North America rather than Africa.


What are the evidences that the earth climate is getting warmer?

Besides rising surface air temperatures other indicators of global warming include -

ocean surface temperatures rising
ocean temperature at varying depths rising
global average sea level rising
Arctic sea ice extent decreasing
Arctic sea ice thickness and average age decreasing
Glacier retreat
Earlier Spring snow melt
Borehole temperatures rising
Earlier budding time of various plants
Less new record low temperatures
More new record high temperatures
Greenland losing ice mass
Antarctica losing ice mass
and etc

Every possible way we can observe and measure the changes we should expect with global warming shows results consistent with actual global warming.
Global Average Temperature as the go to single simple measure is a statistical construct, derived mostly from about 7,000 long running and up to 30,000 current weather stations recording daily minimum and maximums. It is a way to reduce complex change to a single simple number, for convenience. That metric may be a construct but it is constructed to show the extent of change to those recorded temperatures. In one sense it isn't a direct measurement of "something", yet we can confidently expect this average to rise if the climate system is warming - and not rise if it is not.
These weather records allow other kinds of examination besides getting a global average temperature - mapping of regional changes, geographic ones and all the way down to the conditions at individual sites, including their suitability for inclusion in global temperature record calculations. Badly sited ones can be excluded, step temperature changes from changing location or changes to existing location can be adjusted for to achieve better accuracy.
These records don't exist in isolation - there is a broad understanding of climate and weather processes that goes with them. They are also supported by satellite data, such as microwave sounding that allow remote estimation of atmospheric temperatures; whilst they tend to show higher response to El Nino Southern Oscillation, the rates of warming are broadly consistent with weather station records.
It is a reliable observation that in between nearby weather stations sharing similar geography there are similar weather conditions, including similar maximum and minimum temperatures. Consistently different conditions in the spaces between would be noticed and we cannot expect such differences to be confined only in those between spaces; if there were significant variations in the temperatures and rates of change over time in the spaces between locations it would be happening at those locations as well and that would show up in the weather station records. What we find in those records is consistent with global warming.


I strongly recoment using interp2 funtion from Matlab or any other equivalent in other languages. I have used it to do similar tasks.


Is there a website where I can freely download monthly average temperatures per city?

Out here in the Western U.S. the Western Regional Climate Center offers such historical data for download.  If I recall, their downloads are in .csv format, not .json. However, converting data formats is relatively straightforward for GIS software, such as QGIS.


Does Contwoyto Lake empty into both Bathurst Inlet and Chantrey Inlet?

According to "Evaporation from a Small Lake in the
Continental Arctic using Multiple Methods" Nordic Hydrology, 27, 1996, 1-24:

  Drainage from Contwoyto Lake occurs through the Burnside River and Back River

So, yes, to Bathurst Inlet via the Burnside River and to Chantrey Inlet via the Back River.

You can trace out the two paths on the following topo map: http://en-ca.topographic-map.com/places/Contwoyto-Lake-947046/

The Back River outlet is at the south end of the lake and flows through a series of smaller lakes.


On La Vagabonde what Citizen Science is Possible?

Ok, trying an answer. I don't know if citizen science is actually done. Possible would be sample collection, physical data (water temperature, air temperature), weather conditions, sigthings of rubbish, animals or unusual phenomena. Actually, before the space age ships collected and exchanged weather data to produce on ship weather charts for example. Afaik, this is not practical any more, merchant ships anyway and increasingly recreational vessels (if the owner can afford) have satellite data and internet on board.

Data collection in itself is no problem, but the calibration to make them comparable and combinable is. In simple words, one can't just buy a thermometre and bind it to the mast, they'd differ by a lot. Recreative vessels have their routes on the oceans. In Atlantic terms, now (November) they set out in hundreds and thousands into the Caribbean, in spring some them return (the northern route is more strenuous ;-)). There is not that much to be had science wise because they all measure similar things (in between the sunbathing on their catamarans).

And, there actually is concern that too much citizen science could leave a negative carbon footprint.

Something to read: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4159111/


Is porphyritic texture always indicative of a 2 stage cooling process?

Not necessarily. While it is a nice simplification for undergrad textbooks and it nicely explains phenocrysts in some simple basalts, there is much more to it.

Availability of chemical constituents

  Can't the phenocrysts and groundmass be formed at the same time depending upon the chemical constituents forming the rock? The groundmass being made up of constituents least in proportion and the phenocrysts being made up of the constituent in greatest proportion?

In, principle, yes. Think of a granitic porphyry rock with huge feldspars and tiny zircon, apatite and oxides (magnetite, ilmenite, etc) in the groundmass. It could very well be that the feldspars are huge because the rock was rich in Na, Ca, K, Al and Si and it had little Zr, P, Ti and Fe3+, as you would expect from a granite. Even if all minerals were crystallising together, the minerals with the trace components will not grow any larger because there is simply not enough of the elements that make them.

Visual bias

Even if the rock looks porphyrytic, it may not be. Rocks with equally distributed grain size (also called seriate) may sometimes appear to be composed of phenocrysts and groundmass because this is what our brain sees. A seriate rock will have large and small crystals, and usually you will have lots of small crystals sitting just next to the big ones. Our brain tends to ignore the fact that the big ones actually come in all sizes, medium and larger.

Growth rate

It was mentioned in the comments that "Crystal size is essentially a function of how long the crystal has been growing". This is mostly true for a specific crystal, in a known cooling rate, in a defined chemical magma composition, when it perfectly obeys thermodynamic rules, etc. In real natural systems this is not always the case.

For crystals to grow, elements have to be removed from the silicate melt structure and attached to an existing crystal. What if there is no crystal yet? Usually, the formation of crystal nuclei requires a certain amount of undercooling of the silicate melt (up to a few tens of degrees, depending on conditions). Crystals can also nucleate on other minerals or vapour bubbles in the magma (just like bubbles in beer nucleate on the glass and not somewhere in the beer itself).

source: http://www.tulane.edu/~sanelson/eens212/textures_igneous_rocks.htm

However, temperature ideal for nucleation is not always ideal for crystal growth. So in this case, you will end up having lots of small crystals. This varies for different minerals, so one mineral may be in the "growth" field while another will be in the "nucleation" field. This will cause two different mineral sizes as the same time.

Dynamic magma chambers

Recent research shows that our view of a single magma chamber that crystallises slowly or erupts is basically wrong. There are abundant processes that mix and mingle magmas, inject magmas to other magmas, and this sort of stuff. Think of a shallow magma chamber under a volcano that has crystallising clinopyroxene and has some amount of volatiles (CO2, H2O) dissolved in it. This magma is sitting there minding its own business, when suddenly a fresh hot mafic magma is injected from below. Our pyroxene phenocryst-bearing magma is now heated, expands and tries to escape upwards. It decompresses while doing so, nucleating bubbles of gas. The magma is also very undercooled and undersaturated with respect to olivine, so this olivine now crystallises in abundant tiny crystals on the bubbles. In this case, the groundmass actually crystallises when the magma is heated, not when the magma is cooled. Note that this is only an example, not all rocks that look like this formed in the way I described, but it's a possibility.

This is also true for plutonic rocks where the mineral assemblage you see rarely corresponds to the exact composition of the magma from which it crystallised. Crystals can and do move around in magma chambers. This can bring together crystals of different sizes into one place.

Large crystals may not necessarily crystallise from magma

Phenocrysts may nucleate and grow rapidly in water bubbles that exist in the magma, during magmatic conditions (so I'm not talking about zeolites). While the minerals are those you would expect to see in the solid rock after magma solidified, it was favourable for those crystals to grow in the coexisting bubble. This is one explanation (out of many) for the formation of Rapakivi granites.


What are the composition and pressure of the exosphere?

Since this is the Earth Science stack exchange I assume you are talking about the Earth's exosphere, in which case the first issue to decide is how one defines the exosphere - there are several definitions. The lower boundary is straight forward - the thermosphere. However, the exosphere doesn't have a clearly defined upper boundary. You could argue that any gas molecule that is gravitationally bound to Earth is within the exosphere, but that depends upon the relative forces of solar wind and gravity, which is a variable. Some argue that the outer limit is defined by the geocorona at about 10,000 km, whereas the gravitational limit is more than 100,000 km, or arguably up to half the distance to the moon.

The exosphere's composition varies from oxygen, carbon dioxide, hydrogen and helium at its base, to just hydrogen and helium in the outer limits.

The exosphere's pressure is about 0.0007 atmospheres at its base to virtually nothing in the outer reaches. In fact 'pressure' is a meaningless concept in the outer exosphere because individual atoms and molecules are kilometers to hundreds of kilometers apart, so they almost never interact - and pressure is really the intensity of molecular physical interaction.

A comparable argument applies to the exosphere's temperature. In the outer regions of the exosphere the same hydrogen molecule could have a daytime temperature of nearly 2000 Kelvin, and a night-time temperature close to zero Kelvin. In both cases the space would feel cold because there is next to nothing there to transmit heat.

The Earth's atmosphere is still evolving by processes dominated by the lithosphere / biosphere. Only hydrogen and helium are light enough to shoot up to the top of the atmosphere (think helium weather balloons). At the height and temperature of the thermosphere, or higher, they can both gain sufficient thermal kinetic energy from sunlight to gain escape velocity, which is why there is very little helium or free hydrogen in our atmosphere.


Did we ever record a reduction in sea level when the Panama canal was constructed?

It's important to note that major man-made navigational canals often are often routed so that only a smaller bit of new waterways is dug; they are typically made by connecting existing waterways with smaller cut\cuts across higher mountainous areas, plus shortcuts in any place where straightening the route saves significantly.
It seems hard to find detailed construction maps (unfortunate!)  But here is a map of the area before the canal was made from the USF historic maps archive:

Comparing that to the Wikipedia map of the Canal shows two main areas of new waterway creation

However, the largest creation on the map appears to be the expanse of Gatun Lake created by damming the river to create a wider channel (with other connected benefits like power and water storage).  Damming rivers is of course a widespread practice around the world for purposes including water regulation, power generation and agriculture.
Looking at rough estimates of water changes (hopefully with no errors!):
Note these use the US\UK definitions of billion as $10^9$ and trillion as $10^{12}$.  Replace billion with millard and trillion with billion in other regions.

The Culebra Cut "has an average depth of about 43 feet (13 metres) and extends some 8 miles (13 km) to the Pedro Miguel Locks" and "throughout its length the canal has a minimum bottom width of 500 feet (150 metres)" [Brittanica].
So that would be about 7 billion gallons (26 billion liters).
The Wikipedia articles lists Gatun Lake as 4.2 million acre*feet.
That's 1.4 trillion gallons (5.2 trillion liters).
Lake Alajuela is another 150 billion gallons (600 billion liters).

Given that the lakes are the significant amounts of water, 2 trillion gallons (8 trillion liters) would seem an extremely generous estimate for the amount of additional water impounded by the entire system (including widening the river and the water in the Gatun, Pedro Migual, and Miraflores Locks). If assumed all of that ends up being removed from the ocean, averaged over the 140 million square miles (362 million square km) of ocean surface area, that would be roughly 20 micrometers of depth (less than 1/1000th of an inch), comparable to the width of a human hair.  Again, remember that's a very generous estimate.
Given that Wikipedia lists 48 reservoirs around the world that each are more than twice the amount of the water estimated above, it would seem more significant to ask how much those remove in total from ocean.  Still, all those combined would seem only to be on the order of perhaps centimeters of depth lost in aggregate.


Explanation for growing circular echo on weather radar?

You are seeing the gust fronts or outflow boundaries of the thunderstorms around Denver.  The rainfall from the storm provides an evaporative flux that cools the air it falls into (preserving $\theta_e$ of air descending from aloft).  This cool air is more dense than the surrounding air at and near the surface and spreads out as a density current.  The cooler the air (relative to ambient air) the faster it will spread out.  You experience the passage of the boundary as the gusty wind conditions that often precede a storm.

The movement of this density current causes the warmer air it displaces to rise (which can initiate further convection) and this concentrates and lofts insects, which is what you are seeing on radar.  In radar nomenclature you will hear these features referred to as "fine lines".


What is the History of the Brooks Range?

If you extend your map out a little bit further, you will see that the Brooks Range is just a continuation of the Rocky Mountains into Alaska.

Source: freeworldmaps.net, ©Daniel Feher (explicitly permitted use here)

The Brooks Range was formed at the same time as the front ranges of the Rockies in Canada and the Lower 48, during the Laramide Orogeny which lasted from abut 80 million years ago to about 35 million years ago.  This was caused by the subduction of oceanic plates (mainly the Farallon Plate but also the Kula Plate, and to a lesser extent, the Pacific Plate) beneath the west coast of North America.

The Farallon plate went under North America at a shallow angle; because of this, a large part of Western North America was uplifted, deep into the continent, with faults pushing ancient basement rocks up where the Front Ranges and the Brooks Range are today.

Pacific Ocean plates, 55 Ma. Source: Wikimedia Commons

The Kula plate is "all gone", and the Farallon Plate is mostly gone, except for a few remnants like the Juan de Fuca Plate. Because of the different direction that the Pacific Plate moves, subduction ialong the West Coast is mostly gone as the Pacific Plate slides past North America. The shallow subduction that created mountains deep in the interior is done.  A subduction zone further west has created the Aleutian volcanic arc, but this is a much steeper subduction.


Snow from Fire: Could graupel, or even snow, fall from pyrocumulus clouds?

It is likely snowing somewhere in these clouds and graupel exist transiently on their way to becoming hail, but its not likely that you will see either at the surface.

You can make a first order approximation of a pyrocumulus cloud by putting a very strong heat source at the surface in an environment otherwise favorable for severe convection.  What you'll observe is that parcels will easily reach the LFC and you will have tons of CAPE owing to the high surface temperature.  The maximum theoretical updraft velocity is a function of CAPE and so we can expect exceptionally strong updrafts.  This can be confirmed by the observation of severe hail falling from these clouds -- the weight the hailstones can attain increases with updraft velocity.  Because we can observe hail we know that normal moist processes we expect in cumulonimbus clouds are working.

In any mid-latitude cumulonimbus cloud the precipitation starts out as snow. What we experience on the ground is dependent on the temperature profile and this snow either makes it to the surface, melts to be become rain,  melts then becomes supercooled (freezing rain) or melts and refreezes (sleet).  Another option is that the precipitation sublimates or evaporates and never reaches the ground.  The fire driving the storm is likely producing a warm, dry environment at low levels and promoting evaporation of any precipitation.

Graupel will exist as riming and accretion processes are at work, but because of the strong updraft you will end up with hail production and hail at the surface.

To take this approximation into reality you also need to take into account how the fire is modifying the low and mid levels and what kind of aerosols are being emitted by the fire.  The aerosol content could play heavily into the microphysics and precipitation production, but this is not my area of expertise so I won't speculate on the possibilities.


Do rivers/creeks flow underground when they dry up at the surface?

Water in liquid state always takes the fastest route to lower altitude. All rainwater would flow vertically down to the groundwater surface if not the permeability was limited by the material properties.

The permeability controls how fast water infiltrate and penetrate the material. For example, can surface runoff water flow on top of a hard road coating, while water from a watering-can goes into the soft soil in the flower-bed. Gravel, sand and fractured rocks have high permeability whiles shale and non-fractured igneous rock have low permeability. So low, that in many cases it appears to be totally impenetrable on a human time scale.

The same goes for a river. If the river flows on permeable rocks, typical sediments deposited by the river itself (see picture), ground water will also flow in the sediments under the river bed, permitting that water is still entering upstream.

A better way to understand a river or lake in this context, is that it is the surface manifestation of the groundwater table. If you dig a well next to a body of water you’ll reach ground water at the same altitude as the river water surface. The gradient of the groundwater surface and the permeability of the material controls the direction and velocity of the flow.

However, if more water enters a system than the surface can infiltrate, the surplus will flow as surface runoff, typical for wadis (See picture) in desert areas.

So, to answer your question. It depends on the local geology, but ground water will always flow from the precipitation area to the oceans (or a lower point where it can evaporate or being pumped up). Ground water exists everywhere and the gradient of the hydrostatic pressure controls the direction of the flow. As viable rivers shows the ground water table, it is usually rather safe to assume that the ground water under the dry river flows more or less the same direction.

However, ground water flow can be changed by e.g. pumping from irrigation wells. Imagine a flat lying river bed with a well upstream. When enough water is removed from the well and eventually evaporated, ground water will flow towards the well. The water don't 'remember', but follows the law of gravity.


What is this canoe-shaped rock with obsidian? flakes?

Black elongated crystals are mostly hornblendes. The rock itself is (probably) horblende andersite or hornblende dacite. Both are intermediate volcanic rocks.


Where can I get archived hourly wind speed data for Germany?

The MERRA dataset has data for the world from 1979 to date. It updates frequently.

You can get the data as HDF or NETCDF. If your GIS package doesn't read those, there will be translation packages around the web to convert them into a suitable format.

You'll want the U- and V- wind data. You might want pressure too. And possibly even turbulence data.

If you're interested in using this for simulating wind generation, then I highly recommend the paper by Cannon et al on analysing the MERRA data for wind energy simulation.

You might also be interested in the CFSR data, which runs 1979-2010: in connection with using this paper for wind energy simulation, see this paper by Sharp et al.

(I've previously posted this elsewhere on StackExchange)


Why haven't weeds overtaken the entire planet?

A weed is just a plant where you do not want it. Totally a matter of context. Tumbleweeds are non-native, introduced centuries ago. I assume you mean the invasive species of plants that have been spread by humans and are disrupting ecologies throughout most of the world

Until recently, these plants we consider weeds were limited in their range to home environments simply by geographic barriers and surrounding unfriendly environments. And the natural consumers, parasites and competitors in the home environments had adjusted to these plants and kept them in check.

When non-native plants are introduced into a new environment by humans, most of them do not thrive, but occasionally a plant is wildly successful. Eventually the potential consumers, parasites and competitors in that new environment will adjust through evolution. But the tragedy is that many or most of the original species will be destroyed before that balance is restored in a new, way more simplified form. The landscape itself may be totally changed. Removal of a key original species can cause great change too: How Wolves Change Rivers.

Not only will many ecologies be reduced to much simpler versions, even if they eventually conquer the invasive plant, those simplified ecologies will closely resemble each other, if their geography is similar, even if on the other side of the world. If humans were to totally stop transplanting invasive species (collapse of civilization?), diversity would return after millions of years. We know this from Extinction Events.

So to answer you question, weeds before human intervention generally did not take over in their home environments because the potential weeds and their natural consumers, parasites and competitors all evolved together in a quasi-equilibrium. Now, however, most ecologies throughout the world are out of equilibrium because of environmental change and/or invasive species. This will inevitably lead to simplified, usually less robust, weedy ecologies throughout the world. That reduction in diversity might as well be considered a permanent situation compared to the timescale of civilization.


Was Zealandia above water during the last Ice age?

For the most part, no.
New Zealand's North and South Islands likely would have been connected, New Caledonia and other currently existing islands would have been larger, and some now-submerged areas would have been isolated islands that barely poked above the lower sea level at the time of peak glaciation. However, the vast majority of Zealandia is currently over a kilometer beneath the current sea level, which means that it was over 800 meters below sea level during the peak of the most recent glaciation.


What are rare earths and why do they cluster near alkaline magmatism?

"Rare earth" metals consist of Scandium, Yttrium, and 15 other metals of the so-called "Lanthanide" series toward the bottom of the Periodic Table of elements. Basically, these are the chemicals that we didn't study in chemistry class at school.

Like other metals, they have two electrons in the outer shell, but unlike "metallic" chemicals such as sodium or magnesium, they have a special "metal" shell for electrons. They are located at the "left" (relative to the carbon family) or akaline end of the Periodic Table, which is why they are found near alkaline magnatism, in alkaline "compounds."

This is in contrast to the more common chemicals, which are typically found as "oxides," or "sulfides," or possibly in combination with fluorine or chlorine. These common chemical compounds are on the right, or acid side of the periodic table.


Are Earth´s interannual global climate variations affected by other bodies in the solar system and their evolution?

Short answer:

There's probably very little effect, but "entirely independent" is another matter entirely.   There might be some small effect on a year to year, or, for sake of argument, 12 year orbital period of Jupiter.

Long answer.

The precise cause and predictability of (El Nino/La Nina and Neutral), or, lets call it ENSO remains inexact and it's at best, a complex combination of causes and feedbacks.  I'm not precisely sure if it's simply complicate or there are still some unknowns that make any kind of longer term prediction very difficult.  I suspect there's still some unknowns and uncertainty in the longer term causes of ENSO.  This is a pay article, in the summary it says.

  Year-to-year ENSO variability is controlled by a delicate balance of
  amplifying and damping feedbacks

The immediate cause for ENSO seems to be weakening or strengthening of easterly, equatorial, Pacific trade winds.   This makes El Ninos, La Nina's or "Neutral" predictable up to several months in advance but they remain very hard to predict further out than that.

ENSO Explained here with pictures.

and while I generally hate the website, Wattsupwiththat, if you ignore their climate model discussion, their trade wind article is pretty good and the picture below gives a good summary of why trade winds control Pacific surface temperature.

Also, just to clarify "Easterly" winds blow West.  The term means the winds come from the East, just as Northerly winds blow south.   That's why the diagram has easterly's blowing towards Indonesia.

The next logical question is, what causes trade winds to weaken and strengthen and as noted above, that's complicated.  This article says the El Ninos occur every 2 to 7 years, which, while generally cyclical, is a pretty irregular period.

And This article describes the cycle as "flipping and flopping"

Wikipedia touches on the cause of trade winds, but not on the precise mechanisms which strengthen or weaken them.   If the planets, presumably Jupiter being the primary one, has a significant effect, then it's 12 year orbital period should be have a detectable effect and I've never read anything to suggest that it does.

Jupiter does, very slightly affect Earth's orbit and Earth's orbit affects Earth's climate but the effect is small on a 12 year (1 Jupiter orbit) basis.

Earth, relative to the sun, is basically in the same position every season.   Jupiter moves more slowly, so for practical purposes it can be viewed as relatively stationary.    When the Earth is behind Jupiter, it moves through it's orbit a little faster.   When it's ahead of Jupiter, it slows down a little bit.   Also, Jupiter has a tidal effect, where, Earth's orbit stretches in the direction of Jupiter.   These kinds of changes in orbital speed were observed in Uranus and lead to the discovery of the planet Neptune.  For similar reasons,  Jupiter does have an effect on Earth's orbit depending on which side of the solar system it's on, but the effect is small.

I'll skip the math cause I don't do it well enough and it would get long and ugly, but a rough calculation puts an upper limit of the Jupiter effect on Earth's climate as 1/20th of 1% of solar radiation over a few years and then a return in the other direction a few years later, and that's peak season variation, not over a full year.   If winter gets 1/20th of 1% less radiation from the sun, or Summer, 1/20th of more is 1/20th of 1% colder might have a small effect, but not a big one.   That's less than the TSI variation of the sunspot cycle which peaks at about 1/10th of 1% and lasts longer.

I've never heard it argued that Sunspots drive the ENSO cycle, though there is probably some small effect with that too.

Of-course, over much longer periods, Jupiter and to a lesser extent, Saturn likely do effect Earth's ENSO cycle, because Jupiter and Saturn drive Earth's Milankovich cycles, but those happen over periods of 20,000 years and up.   I don't see any way that the 12 year Jupiter orbit has anything more than a very tiny effect.


The causes vary around the world, but we can make some generalizations. Seasonal floods mean that there's more water coming in than going out for only part of the year. If it's annual, the changes are probably related to annual weather patterns in precipitation, temperature, or both. Some big sub-cases are:

(a) in Mediterranean climates, e.g. California, almost all the rain falls in winter in cool weather when evapotranspiration is relatively low. The Central Valley has regions that develop standing water from the rain that falls directly on them because the soil has impermeable clay or hardpan (the vernal pools prairies); and other regions that develop standing water because they're the confluence of several drainages and in wet years the water literally can't flow out to the sea as fast as it comes in (the Yolo Bypass).

(b) If annual precipitation includes a lot of snow and it melts in a hurry, it's common for the downstream rivers to flood at the confluences. There may be years in which the surface snow is melted while the ground is still impermeably frozen, which would turn anyplace level swampy. Parts of Minnesota have bedrock not far under the soil surface and they get this kind of inundation relatively easily.

(c) Where rivers meet the ocean in a long, nearly level bench, high tide (spring tide or storm tide especially) can raise the river level enough that the fields flood. I believe this is the case in the Somerset Levels and in the Netherlands. Some of these are watermeadows and can be quite productive if farmed carefully.

These don't all develop the same kinds of vegetation. For instance, I think I've forgotten a tropical or semitropical case where monsoon rains overwhelm the drainage (possibly the entire Amazon, where the hardwoods are adapted to having their roots underwater even though they aren't flooded all year).


What properties must a rocky body possess in order to exhibit the magnetic dynamo?

Aside from the three requirements already mentioned, electrically conductive fluid, rotation of the planet and convection of the fluid, the main additional requirement is a seed magnetic field.  There must be an initial magnetic field for the dynamo to start.

See the following reference for more information: http://astro.berkeley.edu/~gmarcy/astro160/papers/Magnetic_dynamos_physics.pdf


Can they still not predict rain even one week in advance?

I am going to pause and say I don't know anything about SMHI. Therefore I can't comment on their competency. But I am sure they don't appreciate being called incompetent. If you are so passionate about rain, have you considered looking at weather prediction, and trying to beat them?
It is well known that the limit for predictability of weather is 2 weeks. Past that, climatology is just as accurate as modern forecasts in the grand scheme of things. Individual events may have more or less predictability. Precipitation is very hard to forecast, for various reasons including the lack of quality water vapor observations, the complexity of microphysics, and the interaction with other atmospheric physics.
It really depends on the mechanism for rainfall. Different mechanisms have different amounts of predictability. For example, a 5-day forecast of a hurricane is off by an average of 200 miles (321 km). Thunderstorms, especially individual cells, are hard to predict without probability. Extratropical cyclones are a bit easier predicted.
Farmers almanacs are notoriously inaccurate. Moreover, their "predictions" are fuzzy. You'll find better accuracy with actual forecasts.


Are Indonesian 2018 earthquakes related?

I'll try to answer your second question using the earthquake catalog of the USGS. I encourage you to run your own queries, it's pretty fun and easy to use!

Here is a result of a query for 6+ magnitude earthquakes, starting from 2000, centered around the indonesian archipelago. There is a total of 435 events in the region during this period of time. Now you can download the list as a csv file and have a look at it to get some statistics.

If you sort the events by year, you'll see that there are between 11 (in 2017) and 35 (in 2007) events per year, with a mean of 21.75 events per year. It's hard to get a clear tendency from this graph, although it seems that there was a decrease in activity in the 2011-2018 period.

It gets clearer if you look only at 7+ earthquakes. In this period there are 54 events in the region, but you can see that the vast majority happened in the 2000's, culminating in 2010 with 8 events. Then there is the only year without a 7+ event (2011), and five years in a row with only one event per year. From this graph it also seems that there is an increase in the last two years, with already 3 events in 2019, but I would be careful interpreting this: we lack perspective, and 54 is quite a low number to do a statistically robust analysis.

So from this I'd say there might be an increased seismic activity in the region, although it's too soon to tell for sure. Only time will tell, unfortunately.

Edit: The first question is beyond my competence. It is known that earthquakes redistribute the stress in the lithosphere (see the review by Hardebeck & Okada, 2018). But the tectonic setting is really complicated in Indonesia, with lots of small plates and some unique features, like the divergent double subduction in the Molucca sea (Zhang et al., 2017)... So it's hard to tell if an earthquake here could trigger an earthquake there by modifying the regional stress field.


Over what distance can weather be assumed to be constant?

Weather is subject to Tobler's First Law of Geography: Everything is related to everything else, but near things are more related than distant things.
Temperature- this changes not only by the feature, but also the day of the year. The winter months, as well as the fall and spring, will have much more drastic temperature changes. This may be due to things like fronts, but is ultimately caused by heating differences from the sun. However, a few miles can yield quite a drastic change. Things become even more complicated when elevation is involved.
Precipitation- This is even more variable. Snow can be happening on a mountain, but have rain in a valley. Even the side of a mountain can influence how much rain is seen. I have seen it rain on one side of a building, but not the other. Precipitation is a tricky thing to forecast.
Visibility There are several factors that influence visibility. Fog and precipitation are probably the most common meteorological factors. Elevation can really influence your line of sight. Obviously, visibility is also influenced by the presence of smoke as well as dust.The smaller the particle, the more likely it will obscure vision. And snow tends to be more reflective than rain. Something else that may influence visibility is wind speed, as aforementioned particles can be kicked up from the surface. So visibility will change depending on how all of these change. It may even change depending on the direction you look.

All of this to say is that it really depends and there is rule of thumb.


No, because fresh rainfall has no salt in it, so as long as the river keeps moving the salt has no time to accumulate.

Only stagnant sources of water on land, like lakes with no outlet, can become saline.


Snowing when the actual temperature is around $\small\sf9^o$ Celsius

The clouds in which snow originates must of course be below the freezing point 0°C = 32°F.

Two factors allow snow to reach the surface when the near-ground air temperature is above freezing.

The time delay --- snowflakes may not have time to melt before reaching the surface if the surface temperature is not much above freezing. Strong downdraft air motion and larger snowflakes helps at this, bringing snowflakes down faster.
Once snowflakes fall below the clouds, they are in air at
less than 100% relative humidity. Sublimation --- evaporation
from solid to vapor --- of some snow on the outer edges of a
snowflake can then occur. This removes energy from the snowflake
overall, so it can help keep the rest of the snowflake a few degrees
cooler than the surrounding air.

The highest near-surface (at the official 5 foot height of instrument shelters) air temperature at which I have ever read of snowflakes reaching the ground is 10°C = 50°F.


At what altitude do winds exert the most force?

".....the density of air decreases with height, so the force of high winds aloft are lessened." I can personally vouch for the difference between a 60mph wind at sea level, and one at 14,000 feet! However, however, the single biggest difference between the two altitudes isn't so much the force of that wind, but the consistency of that wind speed, which seems to matter most to wind generation.

Here's how a wind turbine engineer would think of this problem:

From The Engineer's Toolbox- Power generated from the wind

Theoretically power in moving air - or wind - can be calculated

P = 1/2 ρ A v^3
  =  1/8 ρ π d^2 v^3

where
P = power (W)

ρ = density of air (kg/m3)

A = wind mill area perpendicular to the wind (m2)

v = wind velocity (m/s)

π = 3.14....

d = wind mill diameter (m)


How deep does the frost have to go before it becomes permafrost?

Permafrost is permanently frozen ground. However, most definition qualify it as permafrost if it remains frozen for at least two years.

The speed at which a temperature change travels down the ground depends on the thermal conductivity, and it varies between soils. As a thumb rule, the temperature at 10 m depth is pretty much constant and equal to the mean yearly temperature at the surface. This means that 10m is roughly the distance the heat wave travels in a year.

That means that if you manage to freeze the ground below 10m the next summer won't be able to thaw it within a year no matter how hot it is, so it will stay frozen for at least one and a half years. How much longer it will stay frozen will depend on the exact temperatures and lengths of the winter that created the frost layer, the winters after that and the summers in between. Without more details it is impossible to give a number.

Said that, a single cold snap is unlikely to significantly affect the temperature very deep into the ground, you need an extended period of cold weather and many cold winters in a row to do that.

An exceptionally cold winter followed by a mild summer could create a layer of frost that survive two years, but its depth will depend of the actual temperature profile over that period.

Anyway, if that frost layer thaw is not going to be on the next summer, but much later, because the heat will take a long time to travel down there. More on these delay on this answer.


how can a asterisk/star like crack occur on a rock?

Radial fracture is fairly common. It can form from cooling, drying mud, chemical shrinkage, impact, or several other means.  Since you are looking at volcanics you are probably looking at cooling shrinkage, The interior cools slower which means it shrinks more and that's how your get radial fractures. Fractures form perpendicular to whatever the cooling front shape is, a round shaped lava flow produces radial fractures.

Source


How are daily precipitation totals computed?

Typical synoptic (hourly) obs come in about 51 past the hour (sometimes a couple minutes off).  The other reports you're seeing are generally subops (SPECIs) which generally only report precip since the last ob given, but the total of which should always be reflected in the hourly.

So for 2136/2148/2149 timed obshour... you just use the 0.24 from 2149, and it should include the others in it (so skip the others that would lead to double-counting).

On the other hand, the 659 ob being smaller than the 651 ob makes sense... as 659 is in the NEW hour... so would be reflected in the 751 ob (which is indeed higher).

I didn't get a chance to look too closely, but looks like all of these are unfortunately altered forms of the data.  I believe typical full data should have METAR or SPECI in it to indicate which obs you want?

But no big deal, if you look back at the rawer-looking data you gave, looks like you can find which ones you want by looking for the ones with SLP reported right about the end.  Or, even better, just look for the 6**** fields right about the end, which are the 6 hour total precipitation.  Just add the four of those up, and you'll have the daily total.

If you're trying to accomplish all this in Excel, some formulas could be worked up to automatically take what you need from the day's data, or you could use a regex in any of the variety of online regex testers.  Or writing some sort of script could save a lot of time if you're downloading a lot of data.  But the rawer data is often safer and more easy to work with.

I think I used a page like this for more info back in the day when I had to do it.


Could someone tell me what this stone might be

Most likely some form of chalcedony, not knowing where you found it, I'd call it flint, a form of chert.


Where does the biggest land-based ice cap reside?

Antarctica is the ice sheet (cap) that will contribute most IF it would melt completely. The 2013 IPCC report (Ch. 4, the Cryosphere) provides an estimate of 58.3 m of sea level equivalent (sle). Greenland would if completely wasted away provide 7.36 m sle. Remaining glaciers provide an additional 0.41 m sle. The likelihood of Antarctica completely wasting away seems unlikely with our current understanding although the so-called West Antarctic Ice sheet (closes to the Antarctic Penninsula is sitting with its base deep below the current sea level) is far more likely to be lost than the East Antarctic Ice Sheet. Hence the contribution from Antarctica is likely less than the maximum number. Greenland on the other hand is thought to have a "point of no return" beyond which it will irreversibly be lost given the current or warmer climate. Since Greenland is mostly land-based, much of the mass loss will be by surface melting while West-Antarctica can lose much of its mass by ice berg calving which is likely a much faster loss mechanism. Estimates on the scenarios are emerging but there are still uncertainties and there may also be feedbacks that we either do not fully understand or have not yet seen that can change these scenarios (particularly for West-Antarctica). This Science article
published online May 12 2014 is a good example of emerging research on the stability issues of West Antarctica.


Is sea erosion the opposite of sea level rising (or rather, an adjacent phenomenon)?

A paper about this was published yesterday in Nature Climate Change: Sandy coastlines under threat of erosion (Vousdoukas et al. 2020).

  While shoreline change can be the combined result of a wide range of potentially erosive or accretive factors, there is a clear cause and effect relationship between increasing sea levels and shoreline retreat, pointing to increased coastal erosion issues. Climate change will also affect waves and storm surges, which are important drivers of coastal morphology.

The study computes projections of shoreline retreat. They computed four projections: two for 2050, and two for 2100, depending on climate change scenarios (RCP 4.5 and RCP 8.5). Here are the results:

  Assuming that there are no physical limits in potential coastal retreat, by mid-century we project a probable (5th–95th percentile) global average long-term shoreline change, ranging from –78.1 to –1.1 m and –98.1 to 0.3 m, under RCP 4.5 and RCP 8.5, respectively (negative values express erosion). By the end of the century the erosive trend becomes even more dominant and we project a probable range from –164.2 to –14.8 m and –240 to –35.3 m under RCP 4.5 and RCP 8.5, respectively.

And here is how it looks on a map (their figure 1):

The caption reads:

  Projected long-term shoreline changes. a–d, Projected shoreline
  changes by the years 2050 (a,c) and 2100 (b,d) under RCP 4.5 (a,b) and
  RCP 8.5 (c,d). Values represent the median change and
  positive/negative values, respectively, express accretion/erosion in
  metres, relative to 2010. The global average median change is shown in
  the inset text for each case, along with the 5th–95th percentile
  range.

Note that this projected retreat is a combination of two factors: the ambient shoreline change (AC) driven by geological, anthropogenic and other physical factors, and the shoreline retreat due to sea level rise (R). But R is the dominant factor, with a worldwide contribution of 82 % to the total retreat (with regional variations, see their figure 2).

In summary, climate change leads to sea level rise, which in turns leads to coastline erosion. Sea erosion is not the opposite of sea level rising, it is a direct consequence of it.


The effects of biochar burial in California would be so minuscule they might be a net negative once you include the CO2 production of the labor involved. Biochar is a very labor intensive process. Consider carbon in fossil fuels was accumulated of millions of years of what is essentially the same process, even industrializing the process will still take comparable amounts of time to resequester that carbon using what is basically the same method. keep in mind fire is a normal part of many of these environmental cycles they are bad because humans kept preventing the normal fire cycles allowing fuels to build up for decades. Normally that fuel would be cleared by the natural fire cycles. Drought is a trigger not the cause.
Large impact estimates assume we would have to be converting land to biochar production, which has many many downsides and still would not be very effective.
It can be particularly confusing since "Bio-char" can mean two different things, the most touted use of biochar (fertilizer) will have no real carbon sequestration effect but can be a way to offset industrial fertilizers. Burial would sequester some carbon, but would also deplete soils and biodiversity. You have to check and see which use of biochar a source is referring to.
A better idea would be to burn the material as fuel, instead of fossil fuels, which would at least be carbon neutral.
source


I'm sure there are several possible reasons.

I'm not a seismologist, this is an amateur answer only.

Tidal forces

Local acceleration has very small long-term drifts due to tidal forces from the Sun and the Moon. These will have periods of roughly 1 day as the Earth rotates. Most seismometer data will have been run through a high-pass filter with a much higher cutoff frequency than this (of course along with other filtering). This might be implemented with some baseline restoring function other than a simple filter.

Real changes in local g due to displacement in the Earth

Prompt gravity signals -- changes in local g as mass distribution in the Earth changes -- have been detected, and this kind of measurement may become more widely used in the future. Of course a typical seismometer will not be sensitive to pick this up, unless of course your seismometer is sitting atop a substantial geological event!

See:

Prompt gravity signal induced by the 2011 Tohoku-Oki earthquake - could this really be useful for warnings?
Earthquake-induced prompt gravity signals identified in dense array data in Japan
Gravity sensors might offer earlier warning of earthquakes

Instrumental effects

Drift due to thermal changes
Tilt due to geological changes (the z accelerometer is no longer pointing in the same direction)
Tilt due to improperly mounted seismometer that was shaken loose by the earthquake
others...


When sea water evaporates does it carry small amounts of salt into the atmosphere?

Listen to your father ! Yes droplets of spray are carried on the wind several miles . There are any number of corrosion tables listing atmospheric corrosion more severe on sea coasts.  Much of the testing was / is being done at Kure Beach ( N or S ) Carolina.


What are the criteria that make a planet (in)habitable?

Circumstellar habitable zone

There are a few pages that explain the concept in detail, but the gist is that the circumstellar habitable zone is (my definition)

  The region around a star inside which a planet similar to Earth can have liquid water on it surface.

However, with more detailed observations of Europa, with its possible underground ocean, and Titan, with its hydrocarbon lakes, the definition may be modified:

  The region around a star inside which a body can have liquid water, or where other compounds suited for the formation of life can arise; alternatively, the region around a gas giant where moons can be heated by tidal forces such that the compounds can exist.

The latter section, of course applies to moons only. The galactic habitable zone (see here and here) is another - slightly less-well-defined - area where a habitable planet should lie.

You can calculate the habitable zone around a star based off of what defines it: the luminosity of the star, primarily. There's a poorly-explained formula here, although Planetary Biology gives a much more explicit derivation. The two important equations are these:
$$r_i = \sqrt{\frac{L_{\text{star}}}{1.1}}$$
$$r_o = \sqrt{\frac{L_{\text{star}}}{0.53}}$$
where $r_i$ and $r_o$ are the inner and outer radii, and $L_{\text{star}}$ is the luminosity of the star. Note, though, that these are for the conventional definition of the habitable zone, neglecting non-$\ce{H2O}$-based compounds and tidal heating of moons orbiting gas giants. This pre-print, by Kopparapu et al., does give another interesting formula:
$$d=\left(\frac{L/L_{\odot}}{S_{eff}} \right)^{0.5} \text{ AU}$$
where $S_{eff}$ is a parameter determined by the effective temperature $T_{eff}$ of a planet at that distance and some coefficients, as well as the Sun's $S_{eff}$. But those findings are rather new, so I'd stick with the older formulas.

So the habitable zone is determined primarily by the star's luminosity.

Mass

An atmosphere is generally considered a must for planets with Earth-like lifeforms. Low-mass bodies, such as the Moon, can't hold on to one, and that's one of the reasons that moons have not been of as much interest as planets have been. Atmospheres, among other things, can keep the planet at a nice temperature and allow distinct climates to form. As this site elaborates on, they also help protect the planet from radiation like UV rays. Our ozone layer is really helpful in that regard.

Mass isn't the only thing that helps a body keep its atmosphere. For example, Titan is relatively low-mass (although relatively high-mass for moons), yet it still has an atmosphere. This is because the solar wind - which can hurt atmospheres - is so weak at Titan's distance from the Sun.

To expand on what gansub mentioned: Magnetic fields are important because they are extremely useful when it comes to helping a planet retain its atmosphere. As Luhmann and Russell explain in "Mars: Magnetic Field and Magnetosphere", Mars lost its magnetic field long ago, and so the solar wind is gradually stripping it away, albeit at a really slow rate.

Rotation

This section is based a lot on this paper, by Yang et al. It, too is recent, so keep that in mind.

Before I get into the paper, I'll say this: Rotation helps because it keeps one side of the planet from being baked while the other side freezes. Tidally-locked planets aren't the greatest places for life. A decently-fast rotation can really help.

Anyway, Yang et al. came to this conclusion (as voiced in their opening sentence):

  Planetary rotation rate is a key parameter in determining atmospheric circulation and hence the spatial pattern of clouds. Since clouds can exert a dominant control on planetary radiation balance, rotation rate could be critical for determining mean planetary climate.

In other words, rotation helps clouds, and since clouds help govern the climate of the planet, a proper rotation rate can make the climate less extreme.


Recursion relations of Associated Legendre Polynomials with Schmidt Semi-normalization

FYI, the usual reference relied on for the equations used in geomagnetism is:

Langel, R. A. "Chapter four: Main field." Geomagnetism, edited by JA Jacobs (1987).

If it wasn't for lockdown I'd have copied from the book locked in my office to make sure I got it right...but until someone corrects me...
The Schmidt quasi/semi-normalisations for the associated Legendre polynomials are given by these recursions, in the form you'd actually use for calculations typically:

Note that if you use Schmidt normalisation of Legendre polynomials from a given software language to do calculations, you do not want to include the Condon-Shortley phase factor of . So check if it is included in the Legendre polynomial and/or normalisation formula.
Edit: Some links to open source geomagnetism compatible software for calculating Schmidt normalised associated Legendre polynomials.
Python: ChaosMagPy
Python/Fortran-95: SHTools


What is the difference between dew and rain?

Dew is condensate that forms on the surface, usually by the surface cooling to a temperature below the dew point of the air. Thus the water vapr accumulates onto the surface.

Rain is formed by Collision-Coalescence or the Bergeron-Findelsen process. The cloud droplets are formed by the condensation of water vapor on aerosols, when the air reaches supersaturation via the Kelvin Effect and Raoult Effect (which makes up Kohler Theory).


Post-stack seismic impedance (and amplitude) inversion confusion

Here is the figure in question:

"Traveltime inversion" is a very broad category that includes any inverse problem where the input data is a time-delay from a seismic source impulse to when it is received at a seismometer. This includes refraction tomography, reflection tomography, and most implementations of full-waveform inversion (i.e. using diving waves). The output (i.e. what you are solving for) here is a velocity model that best explains all time-delay data simultaneously given the known physics of wave propagation.

"Waveform inversion" is the category that includes all post-migration reflection seismic inverse problems where the input is a single trace or an offset gather (constant X,Y for all input reflections). The output in these are the vertically-varying elastic properties (acoustic impedance, vp/vs, density, etc) that best explain the observed seismic trace/gather (i.e. waveform) given the physics of seismic reflection. This is commonly called "amplitude inversion" because amplitude is one of the main inputs here (although phase and frequency are involved as well).

"Hybrid inversion" is what Yilmaz is calling the recent methods that try to use both the seismic time-delays and ampltidues/waveforms to solve for the best elastic property model that simultaneously explain both types of observations. He cites some recent examples in that paper. The first one I saw on this was Misra and Sacchi (2008). The problem with this stuff is that things become highly nonlinear and therefore require global optimization techniques which are way slower.

"Joint inversion" is just combining different types of geophysical data. For example, let's say you are trying to map the 3D structure of a salt dome. You can use 3D seismic reflection data to map the top of a salt dome easily, but the base is usually really tough due to imaging problems below the salt. Gravity data only gives you the cumulative response of the entire 3D structure below so many salt dome shapes could give you the same gravity response. However, you can use the seismic data to map the top of the salt, then the gravity data to constrain the base, then use that model to re-migrate the seismic data and you should have a good top and base of salt. Similarly, you could pose the problem as a joint-inverse problem where you are looking for the best 3D structural model that simultaneously properly migrates the seismic data and also explains the gravity response.

Hope this helps!


Here are some cities and locations

Average Annual Snowfall for the Following Cities and Locations (in inches)

Asheville, North Carolina: 9.9”

Waynesville, North Carolina: 14.1”

Milwaukee, Wisconsin: 46.9”

Madison, Wisconsin: 50.9”

Syracuse, New York: 123.8”

Buffalo, New York: 94.7”

Smugglers Notch, Vermont: 59.8”

Burlington, Vermont: 59.8”

Mount Washington, New Hampshire: 281.2”

Morristown, New Jersey: 14.1”

New York City, New York: 25.8”

Montpellier, Vermont: 94.2”

Ogden, Utah: 22.1”

Salt Lake City, Utah: 56.2”

Barrow, Alaska: 37.7”

Seattle, Washington: 6.8”

Alta, Utah: 549”


How will climate change affect the latitudinal distribution of precipitation over each latitudinal region?

The continued trend of a warming climate that is expected due to increased GHGs will lead to a net increase in total moisture, since the atmosphere can hold more water vapor at higher temperatures.  In general, the equatorial zones and poles will have a net increase in precipitation while lower mid-latitude zones will have reduced precip, with the rain belt moving poleward.   Climate models generally show a pole-ward shift of extra-tropical precipitation because the increased heat energy allows convective systems in low latitudes to loft the convective air higher up, which in turn leads to greater horizontal transport (generally poleward) before air completely descends and contributes to the development of an associated storm system. You can also expect the poleward shift since cold temperatures accelerate the precipitation process, and since systems will have to travel a little further poleward to reach those cold temperatures.

A 2014 IPCC Technical Summary figure (below) shows change in precipitation forecasted ~65 yrs into the future.  The image on the left represents a best-case scenario if we reduce carbon emissions while the right represents more of a business-as-usual scenario.


How to curb losses during annual heavy rainfalls

Flood control measures largely depend on:

The amount of money available to create flood control measures
The availability of raw materials that could be used to create such
measures
The locality of the potentially flood affected region
The source of potential flooding  and its relation to the region that
could be flooded.

One extreme example is Bangladesh.
Most of Bangladesh is located within the delta region of the Ganges and Brahmaputra Rivers; that is where the two rivers meet the ocean.
The region is flat and devoid of easily accessible sources of natural rock. Elsewhere, competent rock, such a basalt, can be located, extracted and crushed to form aggregate  that can be used as a construction material. Because Bangladesh lacks such rock sources it needs to bake clay to create a form of aggregate.
Being positioned at the tail end of two major rivers, the government of Bangladesh does not have control of significant reaches of the rivers to create flood control structures further upstream.
Politically and religiously, flood control measures on either of these rivers could cause a lot Hindus to become very upset.
Financially, Bangladesh is a poor country with a population of 162 million people. If it were able to construct flood control devices on the two rivers, it would also need to construct flood prevention devices along its coast as the combination of flood waters from the rivers and high tides from the ocean can exacerbate flooding and its effects on the country.
Finally, rising sea levels from climate change are only going to make matters worse for Bangladesh, because it is a very low lying country.

Edit 2 August 2020
Concerning successful flood control measures, two quickly come to mind, the Thames Barrier in London, England and the Aswan Dam in Egypt, particularly the Aswan High Dam.

The Thames Barrier is a movable barrier system that is designed to prevent the floodplain of most of Greater London from being flooded by exceptionally high tides and storm surges moving up from the North Sea. It has been operational since 1982. When needed, it is closed (raised) during high tide; at low tide, it can be opened to restore the river's flow towards the sea.

Based on the success of the Low Dam, then at its maximum utilization, construction of the High Dam became a key objective of the government following the Egyptian Revolution of 1952; with its ability to better control flooding, provide increased water storage for irrigation and generate hydroelectricity the dam was seen as pivotal to Egypt's planned industrialization. Like the earlier implementation, the High Dam has had a significant effect on the economy and culture of Egypt.


Does being under water provide any protection from a asteroid?

No. It depends on the severity. Water would be worse. If an asteroid hit in the ocean we would experience tsunamis the size we get from large magnitude earthquakes. The displacement of the water would be massive. It would also cause things like swimming pools sloshing around, common to the videos you see of hotels from the 2011 Japan earthquake. If it hit on the opposite side of the Earth, land would still be a better spot. Tsunamis can translate vast distances depending on the level of energy and surface deformation they create. Being in a submarine?  Again, no. A tsunamis can pass under boats. However, impact from an asteroid vs sea floor deformation from earthquakes are different functions. The submarine one, would require someone with a little more expertise.


Why is it said that Amazon creates 20% of the oxygen production of the world, when it accounts with less than 14-12.8% of the forest area?

I cannot find any language in peer-reviewed literature (as far as publicly accessible) that makes the 20% claim reported in the question. I therefore consider this claim to be of obscure and dubious origin.

About 50% to 55% of the oxygen produced via photosynthesis is estimated to come from the world's oceans, as reported in the following two papers:

Curtis A. Suttle, "Marine viruses -- Major players in the global ecosystem." Nature Reviews Microbiology 5 (10): 801-12 (2007)

  The oceans cover more than 70% of the Earth’s surface. They control the climate, provide a significant amount of the protein that is consumed globally and produce approximately half of the Earth's oxygen.

A. Yu. Borisov, L. O. Björn, "On oxygen production by photosynthesis: A viewpoint", Photosynthetica (2018) 56: 44

  We also find that the ocean produces 22% more oxygen than the land surface.

According to an expert quoted by the BBC, about 16% of the land-based oxygen production from photosynthesis occurs in the Amazon basin:

  A large proportion of the world's oxygen is produced by plankton, explains Professor Malhi. He says of the oxygen produced by land-based plants, about 16% comes from the Amazon.

Is this claim plausible? Based on the reported size of Amazonian forests at 6-8 million km2 and the world's total forested area of about 40 million km2, I am inclined to answer in the affirmative, although not all of the land-based oxygen production occurs in forested areas.

Yale's Global Forest Atlas:

  Amazon basin is the largest tropical rainforest in the world, covering a size approximately equal to the lower 48 United States. 6-8 million square kilometers of forest house approximately 10% of the world’s biodiversity and 15% of its freshwater.

Based on data from the FAO suborganization of the UN

  Forests cover 31 percent of the world’s land surface, just over 4 billion hectares.

The area of a forest and its oxygen production are unlikely to be in strict linear proportion to one another, as the rate of photosynthesis should depend on such factors as solar irradiation (which varies with latitude and cloud cover) and temperature (in boreal forests) or the seasons (for deciduous forest in moderate climates). The density of a forest will likewise be influenced by the availability of water and nutrients.

How do scientists estimate the amount of oxygen produced via photosynthesis? Best I can tell from a perusal of the literature this is done indirectly by estimating total biomass, which itself is determined by a combination of satellite data and on-the ground measurements. Such estimates carry a non-trivial amount of uncertainty.

Nowak, David J., Robert Hoehn, and Daniel E. Crane. "Oxygen production by urban trees in the United States."
Arboriculture & Urban Forestry. 33 (3): 220-226. (2007)

  The net amount of oxygen produced by a tree during a year is directly related to the amount of carbon sequestered by the tree, which is tied to the accumulation of tree biomass.

S.S. Saatchi, R.A. Houghton, R.C. Dos Santos Alvala, J.V. Soares and Y. Yu,
"Distribution of aboveground live biomass in the Amazon basin",
Global Change Biology (2007) 13, 816-837

  To determine the spatial distribution of forest biomass of the Amazon basin, we report a method based on remote sensing metrics representing various forest structural parameters and environmental variables, and more than 500 plot measurements of forest biomass distributed over the basin. [...] We estimate that the total carbon in forest biomass of the Amazon basin, including the dead and belowground biomass, is 86 PgC with ± 20% uncertainty.


As far as the question "What can be causing this?," there are a variety of reasons. Let's look at the First law of Thermodynamics (including molecular diffusion): $$\frac{DU}{Dt}=c_p\frac{DT}{Dt}=Q-p\frac{D\alpha}{Dt}+\nu \nabla^2 U$$, where $U$ is the internal energy of the ideal gas, $Q$ is diabatic heating, $p$ is pressure, and $\alpha$ is the specific volume, $\nu$ is the molecular diffusivity, and $c_p$ is the isobaric specific heat capacity.

So, without diabatic heating, one way is to change the volume or pressure, which varies the most with changes in altitude (you can rewrite the $-p\frac{D\alpha}{Dt}$ term as $\alpha \frac{Dp}{Dt}\approx \alpha \frac{\partial p}{\partial z}\approx\alpha\rho g=g=-\Gamma_d c_p$, $\Gamma_d$ is the dry adiabatic lapse rate). Using that relationship, (1) may be rewritten as $$\frac{\partial T}{\partial t}=\frac{Q}{c_p}+\nu\nabla^2T-\frac{g}{c_p}-\Gamma_d- \vec{u} \cdot\nabla T$$ Another way is through molecular heat exchange, which is so small it is usually neglected, unless it is in a micrometeorological context. And then there is diabatic heating, perhaps the most loaded term of the equation.

Diabatic heating is any heating source that requires entropy to change. This includes latent heat exchange, radiative heating, etc. Turbulent mixing may arguably be considered in this for large scales, but not small scales.


Are there situations where the groundwater table doesn't follow the morphology of the surface?

The groundwater table depends on a lot of properties. These include precipitation rates, permeability/transmissivity of the subsurface and regional groundwater flow. There are two different regimes that are distinguished: one with a topography-controlled watertable and the other with a recharge-controlled watertable.

A topography-controlled watertable closely follows local topography, while a recharge-controlled watertable only follows the regional topography, and so 'following the morphology' is partly scale dependent. To give an estimate of which regime is more likely at a location, Haitjema and Mitchell-Bruker (2005) studied a number of models and came to the following equation:

$$
\frac{\overline{R}_r}{K} \cdot
\frac{\overline{L}}{\overline{D}} \cdot
\frac{\overline{L}}{z_{\text{max}}}
\left\{
 \begin{array}{ll}
 > m & \text{topography controlled} \\
 < m & \text{recharge controlled}
 \end{array}
\right.
$$

Where the terms have the following meaning:

$R_r$ is the average anual recharge rate
$K$ is the aquifer's hydraulic conductivity
$L$ is the average distance between surface waters
$D$ is the average aquifer thickness
$z_{\text{max}}$ is the maximum distance between the surface water levels and terrain elevation
$m$ is either 8 for one dimensional groundwater flow, or 16 for radial-symmetric groundwater flow (in a circular aquifer).

In cases of a relatively low permeability combined with enough recharge by precipitation the groundwater is likely to follow the surface. However, for example in karst areas, where extensive networks of caves and tunnels in soluble rock cause a very effective drainage over long distances, the groundwater will follow the surface on a much more regional scale. Also, areas with high relief groundwater at least isn't parallel to the surface, and for example in sand dunes, the groundwater level is usually relatively flat compared to the dune.


Permian-Triassic mass extinction. Consequences on Earth's system

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


SOI operates Falkor, which also broadcasts live video. They stream via youtube, currently, as does OET.

https://schmidtocean.org/technology/live-from-rv-falkor/

Occasionally other operations, such as Woods Hole, will operate telepresence cruises, but these three are consistent operators in the space as they have dedicated ROVs and satellite equipment/contracts for their ships. They co-publish an annual supplement to The Oceanography Society's spring issue:  https://tos.org/oceanography/issue/volume-32-issue-01-supplement

-Ethan (formerly with OET)


Why do the dry and moist adiabatic lapse rates converge with height?

If you look closely at the diagram you'll notice height isn't the primary cause for the convergence between the adiabats, though it is the driver.

Note that toward the upper right there is still appreciable difference between the adiabats and as you move to the left the height they converge at decreases.

The reason for this, as your intuition suggests, is that condensation ceases. The reason, simply, is that there is no more water left in the parcel to condense and release latent heat.

Recall the lines of constant water vapor mixing ratio (the lines you use to connect surface dewpoint to the LCL). These lines decrease to toward the left and are sloped steeper than the isotherms. As moist parcels ascend the latent heat release is correlated to decreasing water vapor. At some point we exhaust the water vapor and any further ascent cools at the dry adiabatic lapse rate as there is no more condensation. This is what causes the moist and dry adiabats to become parallel at upper levels (higher for warmer / moist surface conditions and lower for cooler / drier source parcels).

In the comments, concern was expressed that the skew-t isn't capturing the relevant physics, including how a parcel runs out of water vapor.  The skew-t does indeed capture this information and one way you can observe this is by calculating equivalent potential temperature, $\theta_e$.  This temperature is the temperature of a parcel with all of the water vapor condensed out of it. The more moisture in a parcel, the higher the equivalent temperature will be over its actual temperature.  To calculate it on a Skew-T you raise a parcel high enough for the moist and dry adiabats to be parallel, then descend the parcel.  On the way up once saturation is reached you'll ascend via moist adiabat and once the water vapor is exhausted you descend via a dry adiabat.  You can try this for various source parcels and convince yourself that the Skew-T captures these physics.  You should note that the more moist a surface parcel is, the higher it must ascend and the warmer the equivalent temperature will be.


How can the world's sea level rise and fall simultaneously?

There are lots of controls on sea level, not just the volume of water in the world ocean. These controls operate on different time and spatial scales, and interact in nonlinear ways. As a result, both global ('absolute') sea level and local ('relative') sea level can rise in some places and fall in others.

For example, absolute sea-level is currently rising, largely because polar ice is melting. But the rate of change is not the same everywhere, and indeed in some places sea-level is falling:

How can this be? Post-glacial isostatic rebound! Much of northern Canada was covered in a thick ice sheet in the last ice-age. This sheet was heavy enough to depress the lithosphere (the earth's crust)! Since the uppermost mantle ('asthenosphere') is plastic, it flowed out of the say, so to speak. The ice melted thousands of years ago, but the highly viscous asthenosphere is still flowing back, pushing the crust up as it does so. As the crust goes up, relative sea-level falls.

What about global sea-level?

Aside: Some people think changes in global sea-level, sometimes called eustasy, are synchronous and evenly distributed (see early literature on sequence stratigraphy). But, as I hope this tiny introduction will illustrate, it's more complicated than that...

There are lots of other mechanisms that affect sea-level, not just isostacy. Here's a list of Local and Global effects I made for my thesis (Hall, M, 1997, Sequence stratigraphy and early diagensis: the Sobrarbe Formation, Ainsa Basin, Spain, Manchester); I've also blogged about it:

Some effects, like changes in the shape of the geoid and hydro-isostacy, affect the deep ocean too — changing the amount of water that, say, the Pacific can hold. Like all the others, these vary in time and space, and have complex relationships to the other effects in that table... so it's quite hard to model all this!

Footnote: There's lots more on Earth Science Stack exchange about sea-level.


Anywhere on the planet where there is plate convergence probably has rising mountains, even in the ocean where there is back-arc volcanism, although the mountain building may be out of sight from the sea floor. So that includes all of the Andes, much of the European Alps, New Guinea and Indonesia. But there is not much happening in Africa or Australia.


Are there sufficient quantities of limestone to dump in the ocean to reverse acidification?

Getting figures on the amount of limestone available is difficult.

Apparently "limestone makes up at least 10% of the total volume of all sedimentary rocks".

One way to answer your question is by inference. Cement is manufactured from limestone. Current global production of cement is in excess of 3.27 Gt/a and by 2030 it is forecast to be approximately 4.83 Gt/a. Thus if all limestone currently earmarked for cement production were diverted to neutralizing the acidity of the world's oceans it could be done at short notice. How sustainable it would be over the 200 years required, is another matter. It also raises the question of what happens to all the industries and projects that current rely on a cheap and ready supply of cement?

With much tongue in cheek, the Florida peninsular in the US is predominantly limestone, likewise a significant portion of eastern England, with the "white cliffs of Dover, the karst regions of the eastern Adriatic, southern Europe, southern and eastern Asia and the Nullabor Plain in southern Australia. Would these countries be will to sacrifice their lands to neutralize acidity in the worlds oceans?


Why does helium-3 stay in the moon and not escape from it?

The Moon is not "full" of helium-3. 3He is at most fifty parts per billion of the lunar regolith1 and that "high" concentration pertains only to permanently shadowed craters. The Moon is bombarded by a steady stream of helium-3 while sunlit. Some of this incoming helium-3 is temporarily embedded in the lunar regolith. Without this steady supply, the helium-3 content would dissipate at a temperature-dependent rate proportional to the amount of helium-3 in the lunar regolith.

The quantity $q(t)$ of in a cubic meter of lunar regolith is thus dictated by a simple differential equation, $\dot q(t) = \alpha(t) - \beta(T)q(t)$. Time averaging the bombardment and escape rates yields $\dot {\bar q}(t) = \bar{\alpha} - \beta(\bar T)q(t)$. This differential equation yields a steady state value of $\bar q = \bar{\alpha}/\beta(\bar T)$.

1 Cooks, "3He in permanently shadowed lunar polar surfaces", Icarus, 206:2 778-779 (2010).


Determining a rock age using volcanic ash layer

The main interest of tephrochronology (i.e. dating sediments using volcanic ash layer) is specifically its instantaneity (relatively to geological timescale of course). It is precisely used for higher-resolution dating. An example would be the Kawakawa/Oruanui tephra from New Zealand which is a good isochronous marker bed at 26.5 ka, spread over 1500km, but represents probably only a few months of volcanic activity (see e. g. Manville & Wilson 2006)

Important factors vis-à-vis the usefulness of a specific ash layer however are its geographical extent (a volcanic event that will spread an ash layer over a whole basin would be more useful in that it will be used to correlate a large number of sites together) and maybe its volume (you need a minimum amount of material to work with, I'll assume).

Reference: Manville V. & Wilson C. J. N., 2006. The 26.5 ka Oruanui eruption, New Zealand: A review of the roles of volcanism and climate in the post‐eruptive sedimentary response. New Zealand Journal of Geology and Geophysics, 47: 525-547.