How Earth seems quite unique


by Loren Booda
Tags: earth, unique
Ophiolite
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#37
Jul4-09, 07:43 AM
P: 257
There are two principal options:
1. The resurfacing event that occured around 600 million years ago and the stagnant lid period that preceded it, were themselves preceded by 'conventional' plate tectonics.
2. The resurfacing event etc, was the most recent in a series of such events.

You have to dispose of the internal heat. These are the two obvious mechanisms. I have a gut feel - unquantified - that continuous conventional plate tectonics should have maintained water content on the planet, so I lean to the possibility of periodic resurfacing. The evidence is consisten with either.
D H
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#38
Jul4-09, 08:03 AM
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Quote Quote by Richard111 View Post
Ooops, yes. Solar tides. But would that have been sufficient to maintain spin stabilisation? Would the limited range of solar tides have encouraged life to adapt to less exposed land surfaces?
AFAIK, the tides are not the mechanism by which the Moon aids in keeping the Earth's rotation stable. Tides are dissipative forces. The same gravity gradient forces that cause the tides also induce a conservative torque on the Earth as a whole. This torque, averaged out over the Moon's 18.6 year nodical period, results in the 26,000 year lunisolar precession.


Quote Quote by Richard111
Without the moon, life as we know it may not have been possible.
Emphasis mine. This is purely conjectural.


Quote Quote by Richard111
Quote Quote by wikipedia
There is geological and paleontological evidence that the Earth rotated faster and that the Moon was closer to the Earth in the remote past.
I am not debating that the Moon slows the Earth's rotation rate. That is a fact. What is debatable is whether the Earth's day would be eight hours long if the Moon never existed. If indeed the Moon formed from a collision between the Earth and Theia, we do not know how much the collision itself changed the Earth's rotation rate.
Andre
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#39
Jul4-09, 10:45 AM
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Quote Quote by Ophiolite View Post
There are two principal options:
1. The resurfacing event that occured around 600 million years ago and the stagnant lid period that preceded it, were themselves preceded by 'conventional' plate tectonics.
2. The resurfacing event etc, was the most recent in a series of such events.

You have to dispose of the internal heat. These are the two obvious mechanisms. I have a gut feel - unquantified - that continuous conventional plate tectonics should have maintained water content on the planet, so I lean to the possibility of periodic resurfacing. The evidence is consisten with either.
but these are still suppositions following assumptions about heat and heat production in the core, which are also hypotheses. How many times did Venus lose its spinning energy for instance (due to the chaotic zone)? and how about possible relationships there?
Ophiolite
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#40
Jul5-09, 02:53 AM
P: 257
Quote Quote by Andre View Post
but these are still suppositions following assumptions about heat and heat production in the core, which are also hypotheses.
There are no assumptions here, only reasonable deductions leading to plausible hypotheses.
You will note in an earlier post I talk of two principal explanations. I do not rule out other possibilities, but simply find these two are the most probable based upon our current understanding.

Since I also think Venus suffered one or more catastrophic collisions akin to what formed the moon, or stripped mantle from Mercury, then issues of angular momentum cease to be insoluble problems.


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