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Questions tagged [geophysics]

Geophysics is a subject of natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment.

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14 answers
48k views

Why is the pond in my backyard not frozen when it is -15 °C (5 °F) outside?

I am in O'Fallon, Missouri and today it is -15 °C (5 °F) outside. I was taught water freezes at 0 °C (32 °F). I could understand if it was exactly 0 °C (32 °F) that the water might not be turning to ...
Seth Kitchen's user avatar
47 votes
5 answers
33k views

How is the mass of the Earth determined?

According to textbook knowledge, the mass of the earth is about $6 × 10^{24}\,\mathrm{kg}$. How is this number determined when one cannot just weight the earth using regular scales?
Kenshin's user avatar
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44 votes
6 answers
108k views

Are Richter-magnitude 10 earthquakes possible?

The largest earthquake since 1900 according to the United States Geological Survey (USGS) was Richter-9.5 magnitude quake in Chile in 1960. Are magnitude 10 earthquakes possible? If so, what is the ...
blunders's user avatar
  • 4,611
41 votes
2 answers
8k views

Farthest point from the center of the Earth

At first glance, this seems like such a simple question of "What's the highest point on Earth". However, I also know that the Earth isn't perfectly round. So that "highest point" may be in a ...
Richard's user avatar
  • 2,758
37 votes
2 answers
981 views

Similarities between grand circulation solvers and mantle convection solvers

My impression is that both ocean grand circulation models (e.g. MITgcm), and Mantle Convection models (e.g. CitcomS), both use Navier-Stoke's as the governing equation. What are the other major ...
Neo's user avatar
  • 6,456
36 votes
3 answers
16k views

Does gravity increase the closer to the core you get?

Or does the mantle and crust above you counteract the increase at one point and it actually decreases?
HingedHD's user avatar
  • 484
36 votes
3 answers
50k views

Why is Earth's inner core solid?

I have never understood why earth's inner core is solid. Considering that the inner core is made of an iron-nickel alloy (melting point around 1350 C to 1600 C) and the temperature of the inner core ...
tux's user avatar
  • 1,662
35 votes
4 answers
16k 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 ...
Ben A. Noone's user avatar
  • 1,524
33 votes
3 answers
13k views

Is it true that earthquakes are not felt in a cave?

I took a tour of a cave in northern California last weekend. The tour guide asked us, "If an earthquake occurred, what would we feel in here?" My answer was, "fear," but she said we would feel ...
B. Clay Shannon-B. Crow Raven's user avatar
32 votes
8 answers
3k views

Is earthquake prediction possible?

After the Tohoku and East Coast quakes, I skimmed over several books discussing the validity of earthquake prediction as a discipline, yet found no significant breakthroughs. What should change in our ...
Deer Hunter's user avatar
  • 2,103
30 votes
2 answers
23k views

Where on Earth is the magnetic field intensity stronger?

Are there places on Earth that have a strong magnetic field other than the magnetic north and south poles? Can living where (rare) earth magnetic ore is abundant provide a mini-magnetoshere?
Muze's user avatar
  • 1
30 votes
4 answers
40k views

Why is Earth's outer-core liquid?

The Earth's inner core is solid because despite the enormous temperature in this region, there is also enormous pressure there, which in turn raises the melting point of iron and nickel to a value ...
Kenshin's user avatar
  • 7,586
30 votes
3 answers
45k views

Why is Earth's inner core made of an iron-nickel alloy?

This question has puzzled me for a while. I know that earth's mantle is made of different minerals, metals and rocks etc. and that has always made complete sense to me. But why is the inner core made ...
tux's user avatar
  • 1,662
26 votes
7 answers
13k 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 ...
tux's user avatar
  • 1,662
26 votes
2 answers
5k views

What are these undersea lines all around Hawaii?

On Google Earth, there are these radiating undersea lines all around Hawaii: Here with a bit more contrast: Unlike the other lines, they are pointed away (or toward) a single place. What are these, ...
2080's user avatar
  • 371
23 votes
3 answers
12k 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?
Paul's user avatar
  • 1,151
23 votes
2 answers
547 views

What are some of the strongest theories against the existence of mantle plumes?

Among the people I interact with in the geodynamics community, it seems that almost all of us are in full support of the mantle plume theory. What are the strongest arguments against this theory? Is ...
Neo's user avatar
  • 6,456
23 votes
2 answers
5k views

Natural nuclear explosions

I'm aware of the Oklo reactor and other natural nuclear fission reactors, in which geological processes can lead to the formation of a sustained, self-regulating uranium fission reactor. Is it also ...
N. Virgo's user avatar
  • 1,602
23 votes
2 answers
499 views

What properties must a rocky body possess in order to exhibit plate tectonics?

The Earth exhibits plate tectonics, but the other terrestrial planets do not (though Mars and Venus may have exhibited plate tectonics in the past). What is "special" about Earth that allows it to ...
senshin's user avatar
  • 1,885
22 votes
12 answers
7k views

How to quickly or easily prove the world is spherical?

A relative of mine has recently introduced me to the modern flat earth theory, which she believes in. Setting aside for the moment that it is ridiculous, and that sending up some balloons with cameras ...
dutch's user avatar
  • 431
22 votes
3 answers
737 views

Are there any techniques for imaging the deep Earth besides seismic waves?

It is well-known that we can learn a lot about the structure of the lower crust, mantle, and core by observing the ways in which they refract different kinds of seismic waves. Do we have any other ...
senshin's user avatar
  • 1,885
22 votes
1 answer
77k 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 ...
Kenshin's user avatar
  • 7,586
22 votes
3 answers
444 views

Is fracking likely to produce earthquakes?

Post Christchurch-2011 earthquake, there was much concern that fracking in the surrounding areas might lead to further quakes, as was rumoured to have happened elsewhere in the world. Is there ...
Mark Mayo's user avatar
  • 848
22 votes
1 answer
327 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 ...
Paul's user avatar
  • 1,151
21 votes
2 answers
2k views

Why are minerals found in "large" quantities and not scattered throughout the earth as individual atoms?

Heavier elements are created in stars. After stars die they scatter these heavier elements throughout the universe. These elements eventually gather to form planets. But why do we find "chunks" of ...
Zac Patterson's user avatar
21 votes
4 answers
2k views

What would a replacement for SEGY look like?

I have been having a miserable time this week reading SEGY files. This is data from the largest seismic acquisition company in the world whose client is the 7th largest oil company in the world. So if ...
Candid Lunch's user avatar
20 votes
3 answers
5k 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 ...
Kenshin's user avatar
  • 7,586
20 votes
4 answers
17k views

Will the Earth ever stop rotating?

It is well known that the Earth's rotation is slowing down and that millions of years ago there was a point in time where there was only a mere 20 hours in a day on Earth. My question is in two parts....
Kenshin's user avatar
  • 7,586
20 votes
2 answers
939 views

How does one measure what causes earthquakes?

I know that they occur when energy that was previously stored is released in seismic waves. But how is the energy stored in the earth in the first place, and what can trigger the release of such ...
Tom Au's user avatar
  • 2,244
20 votes
3 answers
4k views

Can the overuse of geothermal energy become an environmental concern? [duplicate]

At what power output would we be using so much geothermal energy that we cool the core enough to endanger the Earth's magnetic field and have to stop using it? Is this a conceivable concern for a ...
Mazura's user avatar
  • 495
20 votes
2 answers
48k views

How do seismologists locate the epicenter and focus of an earthquake?

I know the focus of an earthquake is where the earthquake originated from, but what I could never figure out is, how to scientists find out where exactly the focus (and epicenter) are located?
Azzie Rogers's user avatar
  • 2,842
20 votes
1 answer
423 views

Why Earth's magnetic poles are (and were) in their positions?

This is a sort of a follow-up question to What causes the Earth to have magnetic poles? The Earth has magnetic fields, and according to dynamo theory I roughly understand why. If the Earth's rotation ...
Pavel V.'s user avatar
  • 976
20 votes
1 answer
2k views

What causes intra-plate faults, such as the New Madrid fault?

There's been news (some recently) about the New Madrid fault and other active intra-plate faults. For those living in the midwest of the United States, it's been a bit of a shock to learn they have ...
Richard's user avatar
  • 2,758
20 votes
1 answer
2k views

What fraction of dry land is below sea level?

Someone just asked me if it would be practical to counter the rise of sea level by pumping water into storage on land. It struck me that if there is enough land below sea level, this would require ...
mwengler's user avatar
  • 303
19 votes
4 answers
5k views

What would be the first thing which will render the Earth uninhabitable?

There are quite a few things which can make an otherwise habitable planet uninhabitable, and some of these will eventually happen, sooner or later: engulfed by its star when it becomes a red giant ...
vsz's user avatar
  • 464
19 votes
2 answers
17k views

Where is the calmest place on Earth?

I have done some research online, and I've found out that Antarctica has the calmest winds (lowest maximum wind speed) recorded on Earth. However, it is uninhabitable for human life. Other very calm ...
Muze's user avatar
  • 1
19 votes
2 answers
2k views

Why does sea level correspond to boundary between oceanic and continental crust?

Is it a coincidence? the first is determined by the amount of water on the Earth and the second comes from evolution of tectonic plates. Still, oceans seem to fill exactly the oceanic crust.
ceillac's user avatar
  • 293
19 votes
2 answers
654 views

To what accuracy and precision do we know the volume of the Earth?

Satellites such as GOCE and GRACE measure the geoid with unprecedented accuracy. Altimeters can determine local surface elevation with millimetre-precision. This makes me wonder: to what precision ...
gerrit's user avatar
  • 11.7k
19 votes
1 answer
356 views

Can large (and wet) storms really trigger large magnitude Earthquakes?

At the 2011 AGU Fall meeting, this poster claimed that the water erosion from Taiwan's wettest storms could prematurely trigger large magnitude earthquakes , $ M \ge 6.0 $. If this was true, this ...
Neo's user avatar
  • 6,456
19 votes
1 answer
576 views

What are the physical upper bounds on the magnitude of an earthquake?

Given what we know about the physical mechanisms underlying earthquakes, what do the theoretical upper bounds on the magnitude of an earthquake look like? What physical phenomena impose those upper ...
senshin's user avatar
  • 1,885
18 votes
5 answers
11k views

What is the pressure at the center of the Earth?

In the question Does gravity increase the closer to the core you get?, it was determined that gravity reduces to zero at the center of the Earth. That is logical. However if pressure is proportional ...
ralph ellis's user avatar
18 votes
3 answers
1k views

Why is there a line of volcanoes along the northwest coast of North America?

Mount Hood in Oregon is a dormant volcano, and in Washington Mount St. Helens and Mt. Ranier are both active volcanoes. What causes this line of volcanoes running parallel to the coastline along the ...
Chris Mueller's user avatar
18 votes
1 answer
53k views

How long until Earth's core solidifies?

How much longer does Earth have until the core turns solid? Does global warming change these estimates at all?
user avatar
18 votes
2 answers
2k views

Why Vp/Vs and not Vs/Vp?

The relation between shear wave velocity (Vs) and pressure wave velocity (Vp) is often expressed as Vp/Vs. Wouldn't the opposite be more logic? Vs/Vp would never lead to division with zero and the ...
user2821's user avatar
  • 5,946
18 votes
2 answers
866 views

Why is there Uranium in Earth's Crust?

Uranium's density is greater than most elements, so you would expect it to settle to the bottom of a volume of fluid. In the case of the Earth, which was molten in the beginning, you might then expect ...
Cjxcz Odjcayrwl's user avatar
18 votes
0 answers
230 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 ...
N. Virgo's user avatar
  • 1,602
17 votes
2 answers
2k views

What causes the Earth to have magnetic poles?

A compass can tell me the directions of the Earth's North and South poles? What is it about the Earth that produces this "polarity" such that a compass can pick it up? The first thing that jumped ...
Kenshin's user avatar
  • 7,586
17 votes
2 answers
474 views

What geophysical events can (temporarily) increase the Earth's rate of rotation?

My understanding is that the dominant factor behind the slowing of the Earth's rotation (i.e. the lengthening of the day) is tidal friction induced by the Moon's gravity. As seen on the graph below, ...
senshin's user avatar
  • 1,885
17 votes
2 answers
2k views

At what point does plate tectonics stop?

As the core and mantle of the earth cools, it will reach a point where new crust cannot be produced. How can this point be calculated? If we can, has anyone done such calculations? Thanks!
rnrneverdies's user avatar
16 votes
6 answers
962 views

Does volcanic activity fluctuate?

According to this person's surmises, volcanic activity appers to be increasing. However, according to this report, volcanic activity is probably not increasing. My question is: Does Volcanic activity ...
Ben A. Noone's user avatar
  • 1,524

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