<p>No, we occasionally get fragments of upper mantle overthrust onto the Earth's crust, but then the specific gravity (density) contrast is not so great, roughly 2.7 to 3.0 for crust, about 3.2 for mantle. But the core is another matter. The density contrast is huge - the liquid outer core is between 9.9 and 12.2, whilst the solid core is estimated to be 12.6 to 13.0! (High pressure iron-nickel with some denser metals mixed in). Not only that, but the mantle is quite close to the surface, only tens of kilometres deep, whereas the Earth's core is 3000 kilometres below the surface. 
Sadly, there is no volcanic process that comes from even remotely that depth. </p>

<p>Alas - many geologists, myself included, would dearly love to sample the core and compare the composition to iron meteorites (assumed similar). There are many other questions of geochemistry and isotopic composition which might be answered if only we could sample that deep. Unfortunately it is way beyond even the most optimistic advances in technology, so we just have to theorize.</p>

CC BY-SA 3.0
2016-08-17T13:12:26.593Z
The question would also allow for the possibility of the solid solution of core iron into mantle material across the core-mantle boundary. If this is happening, it must be at a very, very low level - and would be difficult if not impossible to trace..
winwaed
CC BY-SA 3.0
2016-08-17T23:57:51.893Z
Regarding winwaed's comment, wherever there is gravity there will be differential density-driven separation of siderophile and lithophile phases. That's maybe not so important at the mantle-core boundary, where the gravity is weak, but 1000 km (for example) above the mantle-core boundary, gravity and temperature will be a strong enough combination for pretty effective differentiation -  the iron phase would have migrated to the core long ago, and especially during the hotter initial phase of planetary formation. That still leaves at least 2000 km to drill before reaching any iron.
Gordon Stanger
CC BY-SA 4.0
2024-06-19T01:11:21.173Z
Gravity is *not* weak at the C-M boundary. Because the core itself is so much denser than the mantle, the gravitational acceleration does not drop off until we actually enter the core and start putting that dense material above us. The C-M boundary is actually the surface of **maximum** gravitational acceleration on Earth.
Oscar Lanzi
CC BY-SA 3.0
2016-08-16T14:50:55.887Z
2016-08-16T14:50:55.887Z
Gordon Stanger
<p>Is the iron in the inner core of Earth trapped forever? Are there any mechanisms that allow some iron to leave the core and come to the surface (eg: magma convention)?</p>

<core><geologic-layers>
Does iron in core have chance to come out to crust?
Gstestso
# Does iron in core have chance to come out to crust?

(Asked by: username_0 on 2016-08-16)

Is the iron in the inner core of Earth trapped forever? Are there any mechanisms that allow some iron to leave the core and come to the surface (eg: magma convention)?

**Tags:** core, geologic-layers


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## 1 answers

### Answer by username_1 on 2016-08-16. Score: 7 | Accepted answer

No, we occasionally get fragments of upper mantle overthrust onto the Earth's crust, but then the specific gravity (density) contrast is not so great, roughly 2.7 to 3.0 for crust, about 3.2 for mantle. But the core is another matter. The density contrast is huge - the liquid outer core is between 9.9 and 12.2, whilst the solid core is estimated to be 12.6 to 13.0! (High pressure iron-nickel with some denser metals mixed in). Not only that, but the mantle is quite close to the surface, only tens of kilometres deep, whereas the Earth's core is 3000 kilometres below the surface.
Sadly, there is no volcanic process that comes from even remotely that depth.

Alas - many geologists, myself included, would dearly love to sample the core and compare the composition to iron meteorites (assumed similar). There are many other questions of geochemistry and isotopic composition which might be answered if only we could sample that deep. Unfortunately it is way beyond even the most optimistic advances in technology, so we just have to theorize.

> **Comments:**
> **username_2**: The question would also allow for the possibility of the solid solution of core iron into mantle material across the core-mantle boundary. If this is happening, it must be at a very, very low level - and would be difficult if not impossible to trace..  
> **username_1**: Regarding username_2's comment, wherever there is gravity there will be differential density-driven separation of siderophile and lithophile phases. That's maybe not so important at the mantle-core boundary, where the gravity is weak, but 1000 km (for example) above the mantle-core boundary, gravity and temperature will be a strong enough combination for pretty effective differentiation -  the iron phase would have migrated to the core long ago, and especially during the hotter initial phase of planetary formation. That still leaves at least 2000 km to drill before reaching any iron.  
> **username_3**: Gravity is *not* weak at the C-M boundary. Because the core itself is so much denser than the mantle, the gravitational acceleration does not drop off until we actually enter the core and start putting that dense material above us. The C-M boundary is actually the surface of **maximum** gravitational acceleration on Earth.  

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