Life and the Goldilocks Planet

[CapelDodger]

Without water, there is no difference between oceanic and continental crust.

The oceans accumulate in the basins formed by the oceanic crust. That's new crust spreading from the mid-ocean ridges. It's denser than continental crust, which is why it tends to subduct under it (while scraping some of the upper, lighter layer off onto the continent). Water has nothing to do with it.

Water has a lot to do with earthquakes and vulcanism, but that's at the executive end of things, plate tectonics represents the policy end. We might learn to influence earthquakes, but we'll never (?) have any say in plate tectonics.

 

[CapelDodger]

I am also at risk of getting in over my head, but, on the subject of the climate models that people use...

Presumably they could 'switch off' the functions that relate to biological processes, which would be easier to organise than arranging for a Gamma Ray Burst to go off in our near vicinity and removal all life experimentally.

Can we hazard a guess at what the model would then do?

I'll hazard it wouldn't be very accurate, at least in the medium-term. Most of the corpsified organic detritus will dry out and burn in the first few years with drastic effects that the models won't account for.

It should be a simple system to model in itself, since it's all inorganic chemistry and relatively few non-linear relationships and feedbacks.

 

[Darth Rotor]

Without life it would never have got to its present state. An oxidising atmosphere is normally unsustainable. If life stopped now, Earth would revert to a reducing atmosphere. It has been said that oxygen was a waste product of early life, and actually poisonous to many primitive organisms.

So perhaps we puny humans do have a purpose, to augment the earth with a byproduct?

George Carlin on Earth and the Environment.

ROFL

DR

 

[H'ethetheth]

The oceans accumulate in the basins formed by the oceanic crust. That's new crust spreading from the mid-ocean ridges. It's denser than continental crust, which is why it tends to subduct under it (while scraping some of the upper, lighter layer off onto the continent). Water has nothing to do with it.

But surely, the oceanic crust is denser because it forms in different circumstances. To say then that water has nothing to do with it seems a bit of a stretch. I could imagine the following:
If all crust is formed in similar non-oceanic circumstances, like on venus, the lack of differences in density is stable. Subduction of a piece of crust will not initiate density differences the way it does here on earth.
On earth, the first piece of oceanic crust that gets subducted wil start producing continental crust, which will then initiate the transition to another equilibrium in which to kinds of crust exist.
I don't think it's strange to entertain the notion that water may be important to the process. It is, as DavidS points out, not as self-evident as I originally thought, but it doesn't seem unreasonable.
But then I haven't started reading yet.

 

[robinson]

The weight of water pushes plates down. I can't remember the figures, but the force of 5 or 6 miles of water was beyond imagining. It is a lot like how the land mass of Antarctica is a mile deeper because of the weight of the ice.