<p>It is extremely unlikely that any hollow volumes exist in the mantle.</p>
<p>The mantle is a convecting solid which can deform over long timescales. Let's assume that such a cavern did somehow form. Whatever it is filled it, would be of lower density than the surrounding rock. It would slowly rise upwards through the solid-yet-deformable mantle until it reaches a place where the rocks are brittle, not ductile. That place is the crust. And as you know, the crust is full of caverns and there is no problem with that.</p>

CC BY-SA 4.0
2021-12-13T04:34:45.180Z
2021-12-13T04:34:45.180Z
Gimelist
<p>mantle isn't liquid, it is a thixotropic substance that flows when pressure decreases and fluids can flow. If there's huge mineral deposits with high melting points there may be pockets. But caverns need a &quot;Floor&quot;.</p>

CC BY-SA 4.0
2021-12-13T07:03:45.567Z
The floor would be towards where the gravity acts. 1g gravity remains similar until the outer core from where it decreases until 0 at the center of Earth.
Giovanni
CC BY-SA 4.0
2021-12-12T23:59:14.717Z
2021-12-12T23:59:14.717Z
LazyReader
<p>Almost everyone wrongly assumes that the Earth's mantle is liquid, but it isn't (only the outer core is). Is it possible then that there are hollow spaces within the mantle, similar to caves in the crust? What could they look like and up to how much of the mantle could be hollow? What might be inside mantle caverns? Would they be filled with gas or rather vacuum?</p>

CC BY-SA 4.0
2023-03-31T17:40:33.877Z
As likely as carvens inside the mantle are
Starship
<plate-tectonics><crust><mantle><cavern>
How likely are caverns inside the mantle?
Giovanni
# How likely are caverns inside the mantle?

(Asked by: username_0 on 2021-12-12)

Almost everyone wrongly assumes that the Earth's mantle is liquid, but it isn't (only the outer core is). Is it possible then that there are hollow spaces within the mantle, similar to caves in the crust? What could they look like and up to how much of the mantle could be hollow? What might be inside mantle caverns? Would they be filled with gas or rather vacuum?

**Tags:** plate-tectonics, crust, mantle, cavern

> **Comments:**
> **username_1**: As likely as carvens inside the mantle are  

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## 2 answers

### Answer by username_2 on 2021-12-13. Score: 1 | Accepted answer

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 it is filled it, would be of lower density than the surrounding rock. It would slowly rise upwards through the solid-yet-deformable mantle until it reaches a place where the rocks are brittle, not ductile. That place is the crust. And as you know, the crust is full of caverns and there is no problem with that.


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### Answer by username_3 on 2021-12-12. Score: 0

mantle isn't liquid, it is a thixotropic substance that flows when pressure decreases and fluids can flow. If there's huge mineral deposits with high melting points there may be pockets. But caverns need a "Floor".

> **Comments:**
> **username_0**: The floor would be towards where the gravity acts. 1g gravity remains similar until the outer core from where it decreases until 0 at the center of Earth.  

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