4 ms·

So if you drill through the crust to the mantle, will magma come up the hole? Will you create a little volcano?

by platz 7y ago

jofer 7y ago
First off, this borehole isn't that deep. Over the continents, you'd need to drill to 40-70km to reach the mantle (sometimes even 100km). However, oceanic crust is much thinner. It is technically feasible to drill into the mantle in ocean basins, where the mantle can be only a few km below the seafloor. Regardless, the mantle isn't molten. It's different types of rocks, but they're still rocks. In fact, the mantle is exposed at the surface in a handful of locations (and a good chunk of the ocean floor). We have learned a lot from what's exposed at the surface, but these rocks have been significantly chemically alerted. Many of the minerals we expect to be there are unstable at near surface conditions. We'd learn a _lot_ from "fresh" mantle rocks If you were to maintain the same temperature but drop the pressure to surface conditions, yes, deep mantle rock would melt. A hole with nothing in it going deep enough would cause a volcano (even if it didn't hit the mantle). However, not all of the mantle is hot enough for that to occur. (Again, the mantle is quite shallow beneath the oceans) We also have to keep the pressure at the bottom of the hole the same as the rock around it, so a well doesn't usually release pressure. At any rate, in any case where you'd try to drill into the mantle, it would be impossible for a volcano to form. All that having been said, geothermal drilling in Iceland has hit magma chambers by accident and caused a "mini volcano".
- Andrew_nenakhov 7y ago
  If the hole is not wide enough, like less than 1m in diameter, then rising magma would likely cool off and seal the shaft long before the flow would reache the surface.
  - K0SM0S 7y ago
    To be fair, it probably isn't the easy approach to drill so thin. Paradoxically (or not), the bigger ones are less of a hassle to manage as you dig deeper.
    - Andrew_nenakhov 7y ago
      Kola Borehole diameter is just 23cm
scohesc 7y ago
I wonder if by the time it gets through 3KM of the relatively thin diameter borehole if it cools and hardens enough to just plug the hole with rock?
micmil 7y ago
No, and no. The mantle is solid. You would have to drill way deep into the mantle before you encountered liquid rock. Volcanoes don't work like that. Even if you drilled directly into a magma chamber, not much would happen. This has been done inadvertently a handful of times. https://phys.org/news/2009-06-scientists-drill-magma.html https://phys.org/news/2009-06-scientists-drill-magma.html Basically volcanoes only happen when there's an extreme amount of pressure from below.
jpalomaki 7y ago
In Indonesia they managed to create a “mud volcano”. And it has been running for years. At peak the daily flow has been 180.000m3 of mud per day. https://en.m.wikipedia.org/wiki/Sidoarjo_mud_flow https://en.m.wikipedia.org/wiki/Sidoarjo_mud_flow

So if you drill through the crust to the mantle, will magma come up the hole? Will you create a little volcano?

by platz 7y ago

So if you drill through the crust to the mantle, will magma come up the hole? Will you create a little volcano?

First off, this borehole isn't that deep. Over the continents, you'd need to drill to 40-70km to reach the mantle (sometimes even 100km). However, oceanic crust is much thinner. It is technically feasible to drill into the mantle in ocean basins, where the mantle can be only a few km below the seafloor. Regardless, the mantle isn't molten. It's different types of rocks, but they're still rocks. In fact, the mantle is exposed at the surface in a handful of locations (and a good chunk of the ocean floor). We have learned a lot from what's exposed at the surface, but these rocks have been significantly chemically alerted. Many of the minerals we expect to be there are unstable at near surface conditions. We'd learn a _lot_ from "fresh" mantle rocks If you were to maintain the same temperature but drop the pressure to surface conditions, yes, deep mantle rock would melt. A hole with nothing in it going deep enough would cause a volcano (even if it didn't hit the mantle). However, not all of the mantle is hot enough for that to occur. (Again, the mantle is quite shallow beneath the oceans) We also have to keep the pressure at the bottom of the hole the same as the rock around it, so a well doesn't usually release pressure. At any rate, in any case where you'd try to drill into the mantle, it would be impossible for a volcano to form. All that having been said, geothermal drilling in Iceland has hit magma chambers by accident and caused a "mini volcano".

Andrew_nenakhov 7y ago
If the hole is not wide enough, like less than 1m in diameter, then rising magma would likely cool off and seal the shaft long before the flow would reache the surface.
- K0SM0S 7y ago
  To be fair, it probably isn't the easy approach to drill so thin. Paradoxically (or not), the bigger ones are less of a hassle to manage as you dig deeper.
  - Andrew_nenakhov 7y ago
    Kola Borehole diameter is just 23cm

scohesc 7y ago

I wonder if by the time it gets through 3KM of the relatively thin diameter borehole if it cools and hardens enough to just plug the hole with rock?

micmil 7y ago

No, and no. The mantle is solid. You would have to drill way deep into the mantle before you encountered liquid rock. Volcanoes don't work like that. Even if you drilled directly into a magma chamber, not much would happen. This has been done inadvertently a handful of times. https://phys.org/news/2009-06-scientists-drill-magma.html https://phys.org/news/2009-06-scientists-drill-magma.html Basically volcanoes only happen when there's an extreme amount of pressure from below.

jpalomaki 7y ago

In Indonesia they managed to create a “mud volcano”. And it has been running for years. At peak the daily flow has been 180.000m3 of mud per day. https://en.m.wikipedia.org/wiki/Sidoarjo_mud_flow https://en.m.wikipedia.org/wiki/Sidoarjo_mud_flow