Cause of plate tectonics?

[garyscott]

Hi all, i have often wondered why Earth has plate tectonics whereas the other bodies in our system do not.

I am probably way off mark on my theory, but i believe that the cause of our tectonic action could go back to the Giant Impact Theory concerning the moon.

If the early Earth was as all other rocky bodies that display no tectonic actions (solid crust over magma layers to core), then would an impact of a planetesimal of the size postulated, in a glancing blow as is generally thought, cause a planet-wide crustal fracturing that would have the longevity to be still in effect today?
The resultant "bubbling" of magma through the cracking would enable shifting of the plates due to the (relative) lubricating effect of the magma, and seawater (through subduction).
I just think that it would explain why we are the only planet with tectonics (afaik) and also fit with the impact theory - one backs up the other - as it were.

I will accept ridicule if i am barking up a wrong tree, but until i hear different, i think my theory could be plausible.

What do fellow orbinauts think?
(If this is in the wrong section, i apologise and ask it be moved to relevant area)

 

[Mattyv]

Scientist don't know why yet:lol:, apparently. They've had some theories about it, but they can't seem to substantiate it with known data. Convection in the mantle is the common one, but again they haven't been able to prove there are convection cells in the mantle. I've also heard tidal forces from the Moon, Earth's rotation, and even the weight of all that water in the oceans.

Basically, We have no clue how it works, just that it almost certainly happens:lol:.

look here, I don't have time to read it all:
http://en.wikipedia.org/wiki/Plate_tectonics#Gravity_related_driving_forces

 

[Cras]

One interesting one was that a massive object hit the Earth, and helped in part create the Moon. This collision blew off a lot of the crust, leaving it thinner than normal, and destabilized and fractured it, creating the plates and the tectonics we see today.

 

[T.Neo]

Plate tectonics is caused by the convection of the mantle; this exerts forces on the crust, slowly moving the plates around.

Small bodies, like the Moon or Mercury, have interiors that have cooled much compared to that of Earth. There is presumably no convection and thus no plate tectonics.

Mars is the same however there are some instances that suggest plate-tectonic-like activity has occured in the past.

Venus is pretty active, just like Earth, but does not exhibit plate tectonics like Earth does- rather a stringy, bumpy surface of volcanic formations. It has been suggested that plate tectonics does not occur on Venus because there is no liquid water to lubricate the crust and allow tectonic plates to move against eachother. Instead, Venus seems to 'bottle up' thermal energy on timescales of hundreds of millions of years, and totally resurface the crust in huge volcanic events.

This collision blew off a lot of the crust, leaving it thinner than normal, and destabilized and fractured it, creating the plates and the tectonics we see today.

It's likely that the collision would have obliterated the crust entirely.

 

[streb2001]

Water also lowers the melting point of the rock when under high pressure allowing the subducted crust to be recycled volcanically. We have plate tectonics on Earth because we have oceans of liquid water. The Earth maintains the correct temperature range because life processes remove carbon dioxide from the atmosphere. Ergo, plate tectonics is caused by life - see Gaia theory!

Mantle convection is pretty much an established fact among earth scientists. Calculations show that, given the rate of heat production from radioactive decay and the plastic properties of the mantle rock at high temperature and pressure, the mantle must be convecting very vigorously. Rather like a pan of boiling stew but over geological time periods.

 

[Mattyv]

Plate tectonics is caused by the convection of the mantle; this exerts forces on the crust, slowly moving the plates around.

Small bodies, like the Moon or Mercury, have interiors that have cooled much compared to that of Earth. There is presumably no convection and thus no plate tectonics.

Mars is the same however there are some instances that suggest plate-tectonic-like activity has occured in the past.

Venus is pretty active, just like Earth, but does not exhibit plate tectonics like Earth does- rather a stringy, bumpy surface of volcanic formations. It has been suggested that plate tectonics does not occur on Venus because there is no liquid water to lubricate the crust and allow tectonic plates to move against eachother. Instead, Venus seems to 'bottle up' thermal energy on timescales of hundreds of millions of years, and totally resurface the crust in huge volcanic events.



It's likely that the collision would have obliterated the crust entirely.

What he said; that's what i've heard about this matter.:thumbup:

 

[Grover]

theres alot of things we dont know about earth, thats why we study other planets, to work out whats different about them, and why Earth DOES support us and other planets dont (besides the lack/surplus of atmosphere and other obvious symptoms of uninhabitable-itis)

personally, i think it may be the delicate balance of elements and substances found in the earths litho-structure. ive got no evidence to support my thoughts, but nobody has ever tried to counter me

 

[streb2001]

This is interesting:

http://www.bbc.co.uk/news/science-environment-16068809

 

[n72.75]

Based on my observations: one out of every four planets have plate tectonics.

 

[C3PO]

Based on my observations: one out of every four planets have plate tectonics.

:thumbup: Spot on! :lol:

I read somewhere that recent GPS measurements have confirmed the stretching of the plate near a subduction zone, confirming the convection theory. The cooler oceanic plate sinks into the mantle, pulling the plates apart at the divergent zone.