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25
votes
1answer
40k views

What is responsible for the underwater waterfall illusion of Mauritius Island?

From an aerial view just off the island of Mauritius, there is what appears be an underwater waterfall. The picture below illustrates this visual phenomenon: The image can also be seen from the ...
34
votes
4answers
13k views

How can we determine the size and composition of Earth's inner core?

From Wikipedia: Earth's inner core is Earth's innermost part and is a primarily solid ball with a radius of about 1,220 km (760 mi). (This is about 70% of the Moon's radius.) It is believed to consist ...
17
votes
0answers
210 views

How much heat is transported from the interior to the surface in the form of hydration enthalpy?

Heat is transferred from the interior to the surface through several methods. One is simply the conduction of sensible heat through the crust - I would guess this accounts for most of it. But some is ...
14
votes
1answer
183 views

What kinds of remote sensing required to observe methanogenic life on Titan?

Inspired by Chris McKay's Possibilities for methanogenic life in liquid methane on the surface of Titan. In the paper, the PI's found that the consumed acetylene, ethane, and other organic solids ...
45
votes
5answers
14k views

Why do snowflakes form into hexagonal structures?

Snowflakes are known to form into pretty hexagonal structures. The image below shows a variety of such structures that are possible (although by all means not an exhaustive list): What is the ...
10
votes
1answer
105 views

Alternatives to Plant Functional Types as parametrisations in land surface models?

Plant Functional Types (PFTs) are a discretisation of global vegetation types. They are used in land surface models to parametrise many values, including albedo, various photosynthesis parameters, and ...
9
votes
2answers
715 views

What tools are available to build unstructured grids for ocean models?

Generating finite element/volume grids is tricky, especially when you are dealing with complex coastlines. What are the more common tools to create the grids and to check the quality (e.g., minimum ...
21
votes
2answers
1k views

What caused the Younger Dryas cold event?

During the termination of the latest ice age the warming climate leading from glacial to interglacial conditions was abruptly reverted by a distinct but short (about 1300 years in duration) cold event,...
43
votes
2answers
5k views

(How long) would Earth's atmosphere last without a global magnetic field?

The Earth's magnetic field provides an important protection against the solar wind (for example, see Wikipedia on Earth's magnetic field and references therein). Mars may have lost its atmosphere ...
24
votes
7answers
11k views

Could the Earth's core lose its heat?

Will all the drilling and digging to use the Earth's natural heat as geothermal energy affect the Earth's core, causing it to cool down? If so, would it result in an ice age? If not, how does the ...
12
votes
1answer
485 views

Did global warming cause the extreme cold 2013-14 winter in North America?

There have been some claims made (example) that global warming had something to do with why the 2013-2014 winter was so cold in the Midwest area of America. If this is true then how did global ...
20
votes
1answer
66k views

Why are oceanic plates denser than continental plates?

In the theory of tectonic plates, at a convergent boundary between a continental plate and an oceanic plate, the denser plate usually subducts underneath the less dense plate. It is well known that ...
14
votes
2answers
2k views

What causes waves to form the characteristic “breaking” shape as they approach the shoreline?

We all know that as waves approach the shallow shores, the waves begin to form a characteristic shape. The upper portion of these breaking waves appears to curl forward and downwards over the bottom ...
12
votes
1answer
4k views

Why does the shoreline sometimes recede prior to a Tsunami?

It is well known among regular beach goers that a sudden shoreline drawback is often a warning sign for an impending Tsunami. My understanding of Tsunamis is they they form as a result of the ...
17
votes
3answers
3k views

How did Earth's plate tectonics start?

Plate tectonics is a theory which describes Earth's lithosphere as being composed of distinct plates which are able to move atop of the underlying asthenosphere. At plate boundaries, this movement ...
12
votes
1answer
141 views

Barite and Acantharians

Acantharians are planktonic protists (abundant in today oceans), sister-group to polycystine Radiolarians, that have the particularity of biomineralizing complex skeletons in strontium sulfate SrSO4 (...
22
votes
2answers
2k views

Peak phosphorus - what are the sinks?

The minable phosphorus reserves are limited. Where is the mined phosphoprus landing, what are the global phosphorus sinks? I would assume that most phosphorus is used for fertilizer and ultimately ...
13
votes
1answer
219 views

Phase changes deep in planetary interiors and their implications for surface tectonics

Earth's core mantle boundary represents a phase change from a solid (though convecting) mantle to a liquid Iron/Nickel core. This dramatic transition is likely the origin of the D" boundary, as well ...
11
votes
3answers
3k views

Why does Earth's outer-core rotate in the opposite direction to the inner-core?

Is it true that Earth's outercore rotates in the opposite direction to Earth's inner-core? Is there a plausible explanation for why this phenomenon occurs and what is the available evidence ...
50
votes
5answers
5k views

What started the US Dust Bowl of the 1930s, and could it happen again?

Most of us know about the Dust Bowl: the huge storms of dirt and dust that swept across America in the 1930's. But what I'm wondering is... What actually triggered the start of the Dust Bowl? Is it ...
11
votes
1answer
787 views

How are organic walled microfossils preserved in the fossil record?

Organic walled microfossils have no hard mineralised parts, how are they preserved in the fossil record?
20
votes
2answers
2k views

In what geological situations can I find gold?

I've heard that gold ore is often associated with quartz veins. What geological processes enable gold particles to naturally cluster together like this? What characteristics/properties should I look ...
18
votes
2answers
6k views

Why does the Hadley cell descend at 30 degrees?

George Hadley's initial model of the Hadley cell described air as being heated at the equator, ascending, and then moving aloft pole-wards where it would cool and descend. Meanwhile surface air would ...
10
votes
1answer
377 views

What evidence is there that plant evolutionary history “dances to a different beat” than that of animals?

Floral transformations have been due to gradual replacement and piecemeal, not mass extinction. Plant “geoevents”; have not been synchronous with epochal animal originations/ extinctions and hence ...
6
votes
1answer
916 views

How can a non-geologist identify a rock? [closed]

I found a rock on a beach in north-east Evia, Greece. Half is light gray, and half is dark gray. There are white (or very light gray) thin lines that form swirls throughout, crossing the light/dark ...
15
votes
2answers
1k views

Why does the El Niño Stop?

The reason for the initiation of the El Niño is unknown, but what is well known is how it progresses once initiated. The West Pacific warm pool begins to drift East, and the strength of the trade ...
12
votes
2answers
147 views

Does anyone know of a DBMS with global geospatial search?

We need to store coverage areas and search by location over arbitrarily large areas. It has to be able to handle polar searches and coverage areas that span multiple hemispheres. No GIS can do this. ...
13
votes
2answers
94 views

Does anyone know of a comprehensive listing of geostationary weather satellites?

Periods of operation at longitude--current as well as historical. The historical list on Wikipedia is incomplete. Is there a single site with status of operational satellites (real-time) or do you ...
12
votes
1answer
259 views

How do mantle plumes travel from the core of Earth to the crust?

As mantle plumes begin in the core and move towards the crust, I would have thought that the heat in the mantle plume would disperse to the surrounding mantle, and the plume would cease to exist by ...
16
votes
2answers
14k views

Coriolis effect and Cyclones

The Coriolis force predicts that winds in the northern hemisphere should be deflected in a clockwise pattern and winds in the southern hemisphere should be deflected in an anti-clockwise pattern. Why ...
7
votes
1answer
1k views

Why do tectonic plates have a tendency to drift closer to the equator?

There are many factors that drive the movement of tectonic plates on the surface of asthenosphere, and some of these factors have a larger contribution than others (e.g. slab suction). One driving ...
16
votes
2answers
347 views

Did the impact event that caused the Chicxulub-Crater definitively and single-handedly cause the Cretaceous-Paleogene extinction?

Opinions abound on the web. What is the state of the current science regarding this theory and what is the best evidence? Is the theory gaining or losing traction? If it's losing what's the best of ...
12
votes
1answer
540 views

Can concretions form in non-sedimentary rocks?

Most modern works (e.g. Nichols 2009; Allaby & Allaby 1999) seem to restrict the definition of ‘concretion’ specifically to formations in sedimentary rocks. I have recently come across a taxonomy ...
22
votes
1answer
311 views

Estimating the permeability tensor of an oil field by remote sensing

I work a lot with numerical methods to solve multiphase flow in porous media for oil applications. In our field, we often use Darcy's law which states that the flux is negatively proportional to the ...
11
votes
2answers
479 views

Equatorial bulge and tectonic plates

It is well known that the Earth is not a sphere, but rather it bulges at the equator. Also it is well known that the Earth's crust is composed of 7 or 8 (depending on definition) major tectonic plates,...
11
votes
1answer
169 views

How do we determine subsurface composition?

Let's assume that a seismogram $s(t)$ is the convolution $s(t)=r(t)g(t)$ between a source signal $r(t)$ and propagation effects $g(t)$. If the source signal $r(t)$ is known, then we can obtain the ...
14
votes
2answers
603 views

Why is a seismogram interpreted as a convolution?

I remember reading in a geology book that a seismogram is a convolution between a source signal and propagation effects. In layman's terms, what does this really mean?
22
votes
3answers
9k views

How to distinguish P, S, Love, and Rayleigh waves in a seismogram?

What features should I look for to determine each of these kinds of waves in a seismogram? What signal processing methods (filters, transforms, etc...) should I use to determine them?
14
votes
2answers
349 views

How are subsurface wave speeds determined without subsurface sensors?

This is something I've never quite understood from a geology class I took years ago: Consider the following picture (courtesy of wikipedia) Obviously, we can't possibly have sensors deep in the ...
13
votes
2answers
936 views

What is a good definition of the word “rock” for teaching?

Note that it needs to include coal and chert, therefore the common answer "a rock is made of minerals" is incomplete.
28
votes
2answers
482 views

What would it take to confirm or refute the Snowball Earth Hypothesis?

Since Harland's sedimentary work and Budyko's models in the 1960s, geologists have hypothesized that the Earth may once have been completely frozen. There are various lines of evidence for this event. ...
16
votes
2answers
17k views

Why does the colour of amethyst fade if exposed to too much light?

It is well known that the purple hue that is characteristic of the amethyst quartz ($\ce{SiO2}$) will fade if the crystal is exposed to light for a prolonged period of time. What is the underlying ...
11
votes
1answer
966 views

Why does the meandering pattern of the jet stream itself propagate?

It is well known that the jet stream follows an overall meandering pattern, but what is less well known is that this meandering pattern itself moves as a wave with a velocity much slower than the ...
25
votes
1answer
811 views

How can the following equations for meandering rivers be theoretically obtained?

It has been observed that the shape of a meandering river is roughly circular, not sinusoidal (Leopold and Wolman 1960). It has also been observed that the following mathematical relationships tends ...
16
votes
3answers
3k views

How does a meandering river form?

I read this explanation about rivers: "As the river erodes laterally, to the right side then the left side, it forms large bends, and then horseshoe-like loops called meanders" Why does the river ...
8
votes
1answer
115 views

Checking the bedrock with radiowaves - how does it work?

I've heard long ago that the rock material deeply below surface are checked by a device that acts like radar - it sends radiowaves into the ground, and geologists find out from reflections that what ...
7
votes
1answer
3k views

What's the difference between the upper & lower mantle?

Recently I checked a picture about the geologic layers of the Earth, and I saw that the mantle is divided into upper and lower mantle. What's the reason of this differentiation?
17
votes
2answers
2k views

Why does a subduction zone produce a serpentinization diapir rather than volcanism?

The classic Troodos Ophiolite in Cyprus has been uplifted by a 'serpentinization event'. Upper mantle (peridotite) has been serpentinized creating a buoyant diapir. This has uplifted the ocean crust ...
9
votes
2answers
2k views

Horizon letter for bedrock

What is the official letter for the bedrock soil horizon? I know that the letters to represent the A, B, and C horizons are widespread, but the fourth layer (bedrock) is referred to with different ...
15
votes
1answer
317 views

Naming convention for sea ice thickness per unit area of ice or ocean

When defining an area average of sea ice thickness, it is important to distinguish between an average taken over an ocean area $$h_1 = \sum \frac{\text{sea ice thickness (in area)}}{\text{area}_\text{...

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