4 ms·

The water in the interior is what matters. It's actually the fact that water is recycled into the Earth's deep interior that's thought to keep it "lubricated",

by Thrymr 12y ago

The water in the interior is what matters. It's actually the fact that water is recycled into the Earth's deep interior that's thought to keep it "lubricated", so to speak, and allow the mantle to flow more readily. For the Earth, that's a feedback loop: water in the mantle allows plate tectonics to work, so water keeps getting recycled into the interior (via saturated crust and sediments) to keep it going.

Terr_ 12y ago
Note, this "water as lubricant" should not be confused with a creationist theory that tries to explain Noah's flood, suggesting that a huge portion of our current surface-water escaped at once.
foobarbecue 12y ago
What do you mean by "lubricated" exactly? The explanation I've had in classes for the "water is essential to plate tectonics" idea is that water causes dehydration melting, and that's thought to be critical to plate tectonics. Adding water to rock decreases the solidus temperature (temperature at which first liquid component is generated).
- kaybe 12y ago
  Yes, this is the current consensus of the scientific community. During subduction of plates (mostly oceanic crust full of water under continental plates of lower density) the volatiles (mostly water) exits the subducting plate and lowers the viscosity and density of the overlying mantle material (viscosity describing the 'fluidness' of the material, higher viscosity = less fluid). The material will then rise up and there will be volcanism, recycling the material back to the surface. This is what you see in most major volcanic arcs, such as the Andes or Japan. The idea that plate tectonics and water are intrinsically linked (at given circumstances) is pretty solidified. The theory of why not such much; the idea above fits our current data best, but data from the planet's interiour is hard to come by and I expect some updates to the theory within a few decades. It's nice that this is currently not critical knowledge for humanity.

by Thrymr 12y ago

Terr_ 12y ago

Note, this "water as lubricant" should not be confused with a creationist theory that tries to explain Noah's flood, suggesting that a huge portion of our current surface-water escaped at once.

foobarbecue 12y ago

What do you mean by "lubricated" exactly? The explanation I've had in classes for the "water is essential to plate tectonics" idea is that water causes dehydration melting, and that's thought to be critical to plate tectonics. Adding water to rock decreases the solidus temperature (temperature at which first liquid component is generated).

kaybe 12y ago
Yes, this is the current consensus of the scientific community. During subduction of plates (mostly oceanic crust full of water under continental plates of lower density) the volatiles (mostly water) exits the subducting plate and lowers the viscosity and density of the overlying mantle material (viscosity describing the 'fluidness' of the material, higher viscosity = less fluid). The material will then rise up and there will be volcanism, recycling the material back to the surface. This is what you see in most major volcanic arcs, such as the Andes or Japan. The idea that plate tectonics and water are intrinsically linked (at given circumstances) is pretty solidified. The theory of why not such much; the idea above fits our current data best, but data from the planet's interiour is hard to come by and I expect some updates to the theory within a few decades. It's nice that this is currently not critical knowledge for humanity.