Does anyone have any ideas about how this could have formed? The website of the project doesn't seem to give much background to the study or location so its hard to even speculate.
Contrary to popular belief the majority of the mantle is not 'mush' but is solid rock albeit slightly 'mushier' than that of the crust at the surface but definately not like the movies!
As I understand it volcanism at mid-ocean ridges is generally caused by the mantle material rising up to fill the void left by the crust being pulled apart (debate about push vs pull for another time!). As it rises up the pressure on it decreases but it's temperature remains roughly constant. This leads to adiabatic melting as the pressure is no longer sufficient to keep the material in a solid state.
So, the question remains as to what process prevented the mantle from undergoing this adiabatic melting. Ideas anyone?
So, the question remains as to what process prevented the mantle from undergoing this adiabatic melting. Ideas anyone?
The rock is peridotite, which is the residue left when mantle partially melts at ridges (or at least thats my understanding of it). This suggests that melting had already occured, the rock had already cooled and the crust (consisting of material melted & removed from the peridotite) that was once overlaying the layer has since been removed.
I'm wrong actually. The rock is serpentinite- a metamorphosed form of peridotite. Interestingly the density of serpentinite is much less than that of peridotite, so adiabatic uplift could be part of the reason we see this rock exposed.
Rank: Topaz
Joined: 18/12/2006
Points: 3010
Yeah, I saw that. I hope they make their findings available on the net as they go along
Geologists are gneiss!!
Rank: Calcite
Joined: 29/01/2006
Points: 158
Does anyone have any ideas about how this could have formed? The website of the project doesn't seem to give much background to the study or location so its hard to even speculate.
Rank: Talc
Joined: 08/01/2006
Points: 45
When they refer to crust, do they mean "Mantle that is more hard then mush? Like frozen magma.
Might the enormous pressure of 3 miles of ocean weighing down on the area discourage the freezing? Discourage the formation of "crust"?
Maybe pressure can be as important a variable as temperature in any material's change of state. If so, then it should also apply to rock.
Or have I got that backwards?
Mike
To me, road cuts serve more as tourist attactions.
Rank: Gypsum
Joined: 14/09/2006
Points: 57
Mike,
Contrary to popular belief the majority of the mantle is not 'mush' but is solid rock albeit slightly 'mushier' than that of the crust at the surface but definately not like the movies!
As I understand it volcanism at mid-ocean ridges is generally caused by the mantle material rising up to fill the void left by the crust being pulled apart (debate about push vs pull for another time!). As it rises up the pressure on it decreases but it's temperature remains roughly constant. This leads to adiabatic melting as the pressure is no longer sufficient to keep the material in a solid state.
So, the question remains as to what process prevented the mantle from undergoing this adiabatic melting. Ideas anyone?
Alex
Rank: Calcite
Joined: 29/01/2006
Points: 158
So, the question remains as to what process prevented the mantle from undergoing this adiabatic melting. Ideas anyone?
The rock is peridotite, which is the residue left when mantle partially melts at ridges (or at least thats my understanding of it). This suggests that melting had already occured, the rock had already cooled and the crust (consisting of material melted & removed from the peridotite) that was once overlaying the layer has since been removed.
Rank: Calcite
Joined: 29/01/2006
Points: 158
I'm wrong actually. The rock is serpentinite- a metamorphosed form of peridotite. Interestingly the density of serpentinite is much less than that of peridotite, so adiabatic uplift could be part of the reason we see this rock exposed.