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
33
votes
4answers
12k 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
1k 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 ...
23
votes
7answers
10k views

Could earth's core lose its heat?

Will all of the drilling and digging to use the earth's natural heat as geothermal energy be affecting Earth's core, causing it to cool down? If so, would it result in an ice age? If not, how does it ...
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!
40
votes
6answers
95k 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 ...
40
votes
2answers
5k 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 ...
36
votes
3answers
31k 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 ...
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
1answer
43k 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?
-3
votes
1answer
409 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
282 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 ...
35
votes
5answers
13k 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?
28
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 ...
22
votes
2answers
342 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
42k 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
5k 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 ...
15
votes
2answers
3k views

How did tectonic plates originally come to form?

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 ...
19
votes
2answers
788 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 ...
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
3answers
2k 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
287 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
2answers
12k 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
712 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, ...
9
votes
1answer
190 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
176 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
179 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 ...
25
votes
3answers
33k 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 ...
29
votes
2answers
7k 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
4k 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 ...
19
votes
1answer
60k 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
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 ...
15
votes
6answers
707 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 ...
11
votes
1answer
247 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-...
9
votes
2answers
477 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 ...
29
votes
4answers
32k 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 ...
19
votes
1answer
304 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 ...
16
votes
2answers
6k 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 ...
16
votes
2answers
585 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 ...
15
votes
1answer
298 views

When a tectonic plate subducts, does any of the subducted material melt, or is it just the mantle above the subducted slab that melts?

I know that water released from oceanic crust causes melting of the mantle in subduction zones, but does any part of the subducted slab melt as well - such as the sediments on the slab or the basalt? ...
14
votes
2answers
325 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 ...
12
votes
1answer
202 views

Why does seismic activity shed light on the inner core rigidity?

Reading Introduction to Geology (MIT 2005) and Wikipedia's article on Earth's inner core, it is specified that: Earth was discovered to have a solid inner core distinct from its liquid outer ...
12
votes
2answers
3k views

Why is colored seismic inversion called 'colored'?

One of the seismic inversion algorithms is called 'colored' inversion. It is performed in the frequency domain and the point is in building an operator that directly transforms a seismic trace into ...
11
votes
5answers
6k views

Why is continental crust less dense than oceanic?

Why is it that continental crust is less dense than oceanic, where in fact continental crust is thicker than oceanic crust?
9
votes
2answers
11k 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.
6
votes
1answer
170 views

Why is ground water rising on these forest rings?

I am seeking a physical explanation for this; There is huge amount of such a Forest rings in Earth; (Link to Google Maps to one ~400 m Ring) They range in diameter from 30 metres to 2 kilometres, ...
6
votes
2answers
2k views

How do seismic charges help to investigate the subsurface?

In the film Kong: Skull Island, scientists investigate an island's structure by dropping explosive charges from helicopters: Source: YouTube trailer In reality, geophysicists do something similar ...
5
votes
1answer
581 views

Is there evidence to delineate where a southern extension of the East African Rift 'plate boundary' is developing?

The East African Rift system is described by James Wood and Alex Guth of Michigan Technological University in the Geology.com web-article East Africa's Great Rift Valley: A Complex Rift System as ...
3
votes
1answer
128 views

Why Earth's outer core does not 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 ...
19
votes
3answers
2k 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 ...