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31 votes

What is the deepest we have ever gone into the Earth?

Probably a bit over 4 km, in this South African mine: https://en.wikipedia.org/wiki/Mponeng_Gold_Mine But as the link mentions, the mine operators go to considerable lengths to reduce the mine ...
jamesqf's user avatar
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23 votes
Accepted

What do continents "lay" on?

Matan, the continents where we all live "float" on the Earth's mantle. The continents are made out of relatively brittle rock called the "Crust" and the mantle is made out of much more ductile ...
Antonio's user avatar
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19 votes

What is the deepest we have ever gone into the Earth?

Since you termed it based on sea level, the gold mines in South Africa are not the deepest, they begin at an elevation of ~1500 m, meaning their 4 km depth is only 2.5 km below sea level. The Kidd ...
Josh King's user avatar
  • 321
14 votes
Accepted

If people aim to reach the mantle, why don't they just use volcano craters?

why don't they just use volcano craters? Because volcano craters don't go to the mantle. Here's a sketch of how the crust, mantle, and volcanoes look like: Tan colour is crust, orange is mantle. ...
Gimelist's user avatar
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11 votes
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What's the official reason why it became so hot in the Kola borehole?

Unfortunately, you intuition about subterranean ground temperatures is incorrect. Basements and cellars do provide cooler conditions to store perishable items because the near surface rock insulates ...
Fred's user avatar
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9 votes
Accepted

How can we have "floating" and convection currents in a non-liquid mantle?

Is the mantle solid? It's all a matter of timescales. The mantle is undoubtedly solid (except locally in the uppermost regions where melting can occur) but on a long enough timescale it can display ...
bon's user avatar
  • 2,211
7 votes

How can we have "floating" and convection currents in a non-liquid mantle?

Humans have difficulty visualizing how rocks flow because the required conditions are outside our everyday experience. We are familiar with surface temperatures and pressures, and geologically short ...
Gordon Stanger's user avatar
7 votes

How is dense magma able to rise and punch through continental crust?

Your intuition is quite correct: Other factors being equall, a dense magma will not rise through lighter rocks. The exception is if it is under pressure, in which case a fluid magma will escape ...
Gordon Stanger's user avatar
6 votes
Accepted

How straight is the Kola superdeep borehole?

Borehole drifted from straight vertical by ~840 meters over 12,000 meters. All drill-bore wander side to side some and Kola borehole did not drift much until depth exceeded 5000 meters. See page ...
Earth Science Expatriate's user avatar
6 votes

Do we know what the rigid mantle looks like?

Above the asthenosphere is the lithosphere. The main constituent of the lower lithosphere is peridotite, a coarse-grained igneous rock containing the minerals olivine and pyroxene. Samples of ...
A. Newell's user avatar
  • 288
6 votes

Why is the concentration of highly siderophile elements so uniform in the mantle?

First, note that this plot is normalized to a reference, here the composition of CI chondrites (your version lacks the Y axis label, it's figure 2.1 from Walker 2016). So if the concentration of ...
Jean-Marie Prival's user avatar
5 votes

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

From the comments: And indeed, after browsing trough a few sections they seem to assume that "Liquid metal separates rapidly from liquid silicate", like oil and water, and they don't mix ...
Gimelist's user avatar
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5 votes
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How can isostatic compensation of the crust be reconciled with a relatively strong upper mantle?

Because it is not the strong portion that gets displaced. The mantle just below the crust bends, just like the crust above it, together they make up the lithosphere, It is not the thing being ...
John's user avatar
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5 votes

What is meant by phase-change in mantle?

I'd like to add to Gordon's answer. A phase change in this context does not only refer to the change in the state of matter (e.g. liquid to solid) but a change in different solid states as well. ...
Gimelist's user avatar
  • 23.2k
5 votes

Do we know what the rigid mantle looks like?

To complete the first answer with bigger scale images, here are some pictures of well-known mantle outcrops in Italy and Corsica (figure 4 from Rampone et al. 2020): The caption reads: (a) ...
Jean-Marie Prival's user avatar
5 votes

From how deep in the mantle has any rock ever been brought to the surface? Have scientists found anything they believe originated in the outer core?

Diamond is stable at high temperatures only under very high pressures. Mineral inclusions in a diamond, and the rocks in which a diamond are embedded, can offer further clues as to the depth from ...
nigel222's user avatar
  • 161
4 votes

What do continents "lay" on?

There is no ocean of magma, magma only forms below when rocks have been melted due to various causes like flux melting and heat decompression, the only part of the earth that is liquid is the outer ...
Haule's user avatar
  • 39
4 votes

How can we have "floating" and convection currents in a non-liquid mantle?

I'd like to add to the correct answers already given. Solids can flow and deform without being a liquid. You can bend iron bars. You can dent plastic. You can squeeze nylon bags. The cotton on your t-...
Gimelist's user avatar
  • 23.2k
4 votes

What is meant by phase-change in mantle?

'Phase change' doesn't just mean liquid-gas-solid changes. It also includes mineral lattice restructuring in response to differing pressure-temperature conditions. There are also other solid-solid ...
Gordon Stanger's user avatar
4 votes

Do there exist reasonable numbers on the density/radius/mass of the various geological layers of the Earth?

One model that will help you is the admittedly dated (1981) Preliminary Reference Earth Model. It provides density models for the inner and outer core as functions of distance from the center of the ...
David Hammen's user avatar
  • 23.7k
4 votes

When diamonds "migrate" from deep underground to the surface, do they maintain pressure inside when there is no more pressure outside? If so, how?

The question is in regard to pressure confining a rare, deep-mantle formed mineral visible within a diamond inclusion. The pressure on the inclusion within the diamond crystal is really the pressure ...
Thomas Perry's user avatar
4 votes
Accepted

What is the difference between a depleted mantle, and a fertile or enriched mantle?

Basically, a fertile mantle is a portion of mantle that has not experienced any melting. On the other hand, a depleted mantle has experienced partial melting, and subsequent extraction of this melt. ...
Jean-Marie Prival's user avatar
4 votes
Accepted

Why was quartz not a major product of the Lunar Magma Ocean?

Fractional crystallization indeed makes magmas more silicic. However, you'll never reach a magma composition with 100 % silica, which could then cool and crystallize as quartz. The starting material (...
Jean-Marie Prival's user avatar
4 votes

If the universe (and our galaxy) has about twice as many oxygen atoms as carbon ones, why does Earth have 300 times as many oxygen atoms as carbon?

As the comments suggest, there probably is no one factor, but a big one seems to be the gas and ice giants took most of the carbon away. In our Solar System as a whole, the primordial nebula had ...
Oscar Lanzi's user avatar
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4 votes

From how deep in the mantle has any rock ever been brought to the surface? Have scientists found anything they believe originated in the outer core?

As far as I know the best estimate is "upper mantle" from mantle xenoliths but that's not terribly specific. I am not sure if knowing more than that is possible right now.
Ian's user avatar
  • 41
3 votes

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

This is an interesting question that is maybe a little misguided. Instead of answering your question directly I'd like to draw your attention to some things that might get you to rethink your ...
g.z.'s user avatar
  • 380
3 votes

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

I've already commented on this before here. This will not work regardless of whether this is iron or lead or anything else. The fact that it was published in Nature does not mean it is true, always ...
Gimelist's user avatar
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