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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 ...
  • 1,698
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 ...
  • 291
14 votes
Accepted

What's it like inside a natural gas cavern on Earth?

A cavern filled with natural gas would look like an ordinary cavern. However, natural gas is rarely abundant in caverns. Most natural gas reservoirs occur in the pore spaces of sandstones. These pore ...
  • 10.8k
6 votes

How did they know that there was a "desert tsunami" in a Death Valley cave after a 7.6 magnitude earthquake near the southwest of Mexico?

The news section of the Death Valley National Park website has the story: Mexican earthquake sloshes Devils Hole. There is footage of the waves at the end of the page. Here is a screenshot from the ...
5 votes
Accepted

What kind of lava tube feature is Cleopatra's Grave?

It's just average ropy lava called pahoehoe by geologists. It's similar to dough so it easily forms ropes like the ones around the side and bulbs like the central area which is similar to a pillow ...
4 votes

What's it like inside a natural gas cavern on Earth?

According to 3-D Printing Artificial Reservoir Rocks to Test Their Petrophysical Properties Pore sizes of typical reservoir sandstone range from 0.1 to 100s of microns.
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3 votes

How did they know that there was a "desert tsunami" in a Death Valley cave after a 7.6 magnitude earthquake near the southwest of Mexico?

As to the how did they know, and how did they register: The observations are a byproduct of the conservation efforts at the cave. The Devils Hole pupfish are an endangered species that are observed by ...
  • 31
2 votes

How strong/hard are speleothems?

The speleothems are made of calcite, so breaking one small stalactite is same as breaking one narrow "straw" of calcite. Calcite is not so strong, so it is pretty easy to break small ...
  • 628
1 vote
Accepted

How likely are caverns inside the mantle?

It is extremely unlikely that any hollow volumes exist in the mantle. The mantle is a convecting solid which can deform over long timescales. Let's assume that such a cavern did somehow form. Whatever ...
  • 22.3k
1 vote

Possible cavern?

It is extremely unlikely to be a sink hole. They are characteristic of waterlogged limestone country such as is found in Florida. Hollows are sometimes found in flows of igneous rock where there has ...
1 vote

Why are there no deep caves in the continental US?

Deep caves primarily need two things: 1) Very thick or extensive tilted limestone beds so that there is enough bedrock to form a deep cave, and 2) A deep water table so that caves can form by ...
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1 vote

How are Benagil caves formed?

How are they formed? Erosion. Long version: The rock/cliff the cave is set in possesses different hard/softness. Some parts of it are more prone to erosion than others. Erosion comes in the form of ...
  • 826

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