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.

Filter by
Sorted by
Tagged with
34
votes
4answers
14k 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 ...
14
votes
1answer
2k views

What are the causes of the supercontinent cycle?

Throughout geologic history, Earth's continents have broken apart and come together to form supercontinents multiple times, in a somewhat regular period, known as the supercontinent cycle. The length ...
36
votes
3answers
35k 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 ...
26
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 ...
19
votes
1answer
1k 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 ...
16
votes
2answers
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!
44
votes
6answers
102k 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 ...
41
votes
2answers
6k 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 ...
18
votes
1answer
52k 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?
9
votes
2answers
661 views

What are the striations or ridges in the eastern Pacific Ocean?

Messing around on Google Earth recently I noticed a number of striations in the Eastern Pacific. These appear in an East-West orientation and seem to start on the North and South American continental ...
8
votes
1answer
11k views

Why does the wind periodically change direction?

Image Subtitle: Wind going across the page - and changing direction To clarify, imagine you were sat in a boat in the middle of a lake recording the wind direction every minute. You notice that the ...
-3
votes
1answer
1k views

Safest spots when an asteroid hits? [closed]

I am breaking this question and no longer making an effort in refining it with the exception of adding an associated link with the scenarios. I always wondered if a devastating asteroid was ...
19
votes
1answer
302 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 ...
17
votes
3answers
4k 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 ...
13
votes
1answer
3k views

How much water is the atmosphere losing to space?

Up until recently, I was under a (wrong) impression that the amount of planetary cumulative water resources was finite as I believed its escape from the atmosphere was impossible. I believed that, ...
8
votes
3answers
820 views

What is the total Earth's interior energy budget?

What is the total Earth's interior energy budget? What is the heat flux per m2 that warms the Earth surface because of the Earthy's internal heat. How much of that heat is replenished from the ...
37
votes
5answers
23k 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?
30
votes
8answers
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 ...
23
votes
2answers
372 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 ...
19
votes
2answers
44k 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?
18
votes
2answers
7k 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 ...
16
votes
2answers
654 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 ...
9
votes
2answers
1k views

How do Rossby Waves in the ocean form?

So on land, I believe that one factor in their formation is due to inhomogeneities in surface heating between land and ocean (and also inhomogeneities in surface heating due to terrain effects like ...
19
votes
2answers
844 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 ...
18
votes
2answers
993 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 ...
15
votes
1answer
2k views

Can impact events cause widespread volcanic activity on the other side of the planet?

The currently accepted theory for P-T mass extinction is environmental change triggered by the Siberian Traps volcanic activity. A paper(1) suggests that the Siberian Traps were caused by a hotspot ...
11
votes
2answers
461 views

Change in earth mass since the time of the dinosaurs

Is there a significant difference in the mass of the Earth between now and the time of the dinosaurs (250 - 75 million years ago)? I was just wondering if the force of gravity on dinosaurs would have ...
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 ...
11
votes
2answers
14k views

How do I derive the formula for lithostatic (overburden) pressure?

The title pretty much says it. I have the formula: $P = \rho g h$ where $\rho$ is the density, $h$ is how deep the pressure is in the Earth and $g$ is the gravitational acceleration(?). I don't get ...
9
votes
1answer
208 views

What is the current status of geophysical global cooling theory?

Plate tectonics effectively rubbished the theory of geophysical global cooling as a means of explaining many surface features on the Earth. However, this wiki says that the same process is responsible ...
6
votes
2answers
212 views

Why are pole reversals not more detrimental to life?

This question is linked to the following question, and has two parts. Mars interdicts approximately 40% of the radiation (per square meter) of the sun that Earth does. It has been claimed that Mars ...
4
votes
1answer
245 views

If all the world's ice were to melt, would this shift the earth's centre of gravity with consequential effects on sea levels?

This question on Maths SE asked how we might calculate the effect on sea level if all the world's ice (ie including the whole Antarctic ice sheet) were to melt. I posted an answer containing ...
3
votes
3answers
3k views

Why is the density of Earth higher at the core

If gravitation decreases as we approach the core and if density is a function of gravity we should expect a void core. Unless the accretion disk was formed starting with the objects of highest mass ...
2
votes
1answer
154 views

Why the “Mission to Earth’s core” proposal suggests using liquid iron instead of lead?

Nature communications article "Mission to Earth's core — a modest proposal", suggests placing a large volume of liquid iron in a crack and let it sink all the way to the Earth's core, carrying along a ...
26
votes
3answers
38k 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 ...
36
votes
3answers
9k 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?
30
votes
2answers
12k 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?
18
votes
4answers
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 ...
18
votes
9answers
6k 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 ...
20
votes
1answer
338 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 ...
20
votes
1answer
67k 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 ...
16
votes
6answers
785 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 ...
12
votes
1answer
2k views

Should one extract wavelet from seismic or well log for the generation of synthetic traces?

Synthetics are generated by convolving reflectivity series with the known wavelet. I have seen most of the wavelet are extracted from seismic data itself. Is there any hard and fast rule, or can one ...
12
votes
1answer
1k views

Why is ocean surface velocity around 3% of wind velocity?

Many introductory level textbooks suggest that, as a rule of thumb, the velocity of the ocean surface is around 3% the wind velocity at 10 meters above the sea surface. For instance, Ocean ...
11
votes
1answer
269 views

What happens to the higher frequency content of the tremors associated with a volcanic eruption?

From [1]: The main characteristics of volcanic tremor depend strongly on whether a volcano is erupting explosively and on the intensity of the event. Long before an eruption, tremor is ‘narrow-band’ (...
9
votes
3answers
13k views

Why is the lithostatic pressure gradient 1 psi/ft? How is it derived from density?

Why is the geostatic (or is it the lithostatic?) gradient 1 psi/ft? How is that derived from g/cc? Thanks.
8
votes
1answer
3k views

Changes in Earth's orbital and rotation speeds

What are the Earth's maximum and minimum orbital speeds around the Sun? Is there any way to calculate orbital speed at any point of Earth's orbit? Is there a way to relate this to the calendar? Does ...
6
votes
2answers
417 views

Why doesn't the Earth's outer core dissolve into the mantle?

It is well accepted that the outer core is made out of liquid iron and nickel, and as everything else it should tend to reach chemical equilibrium with its surrounding. In particular, I would expect ...
30
votes
4answers
36k 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 ...
16
votes
2answers
8k views

Why is the inside of the Earth so hot?

I have heard that the Earth is made up of four layers, being the crust, the mantle, the outer core and the inner core. I have also heard that the Earth's temperature increases as you move from the ...