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Tom Mazanec
2017-Mar-12, 06:00 PM
I don't believe in perpetual motion, something is powering plate tectonics. Eventually the needle will reach E.
How long will this take?

Ara Pacis
2017-Mar-12, 08:37 PM
The Earth may be destroyed by the sun before then. Before being swallowed, the oceans will evaporate and that might seize up whatever's still going on with the plates.

Tom Mazanec
2017-Mar-12, 09:08 PM
Good point.
But just for curiosity's sake, assume the Earth is eternal and the "machine" will eventually stop.

Noclevername
2017-Mar-13, 12:13 AM
Radioactive decay in the interior of Earth powers plate tectonics. How long will it last is an open question.

geonuc
2017-Mar-13, 09:13 AM
Radioactive decay in the interior of Earth powers plate tectonics. How long will it last is an open question.
Plus residual heat from formation.

Noclevername
2017-Mar-13, 10:32 AM
Plus residual heat from formation.

IIRC that had already run out.

lpetrich
2017-Mar-13, 11:47 AM
Decay of uranium-238 and thorium-232 will continue to provide enough heat for plate tectonics for at least the next few billion years. Their half-lives are 4.5 and 14.05 billion years. But how much is too little heat to power plate tectonics is difficult to say. Also happening before much of the remaining U-238 and Th-232 decays is loss of water by evaporation into space. Lack of water for lowering the melting point of rock will make subduction more difficult, and may stop the plates.

grapes
2017-Mar-13, 02:31 PM
IIRC that had already run out.
I thought estimates put it at 40% to 60% of the total. Guess I gotta look into that. :)

ETA:
The Naked Scientists seem to say both radioactivity and primordial heat are important, but don't give specifics.
https://www.thenakedscientists.com/articles/questions/what-causes-tectonic-plates-move

geonuc
2017-Mar-13, 10:04 PM
I thought estimates put it at 40% to 60% of the total.

That's about it from what I know and from online sources.

ETA: Such as this one from the American Geophysical Union:

http://blogs.agu.org/martianchronicles/2013/01/24/where-does-earth-get-its-heat/


... simple decay of radioactive isotopes provides about half of the Earthís heat, and will continue to provide heat for billions of years. The rest of the heat is left over from the planetís formation.

Bearded One
2017-Mar-15, 01:44 AM
How much heating is caused by tidal flexing from the Moon?

eagledare
2017-Apr-18, 09:04 PM
Plate tectonics with the old theory of a fixed size Earth is something of the past unless someone can prove the subduction zones between the ocean ridges as seen in https://www.universetoday.com/131459/mid-atlantic-ridge/ .Can anyone spot the subduction zones between ridges. All I see is continents. The latest theory is the Expanding or Growing Earth theory that makes much more sense than the current theory. If Earth is growing it is not perpetual motion but Energy converted to matter, a whole new field of study is needed, See these links on Expanding Earth. https://youtu.be/oJfBSc6e7QQ?list=PL5A1097F4E958728D , https://www.youtube.com/watch?v=swCnPOi5qOU , http://www.dinox.org/ .

slang
2017-Apr-18, 09:45 PM
Welcome back, eagledare, it's been a while. :)

As you haven't posted in over 10 years it's fair to assume that you may have forgotten the rules we have here on Against The Mainstream posts. For one, they may only be posted in the ATM sub-forum, where special rules apply (rule #13). Second, part of rule 13 is that you may present an ATM theory only once, and need moderator permission to post on that topic again. Since you already had a thread on an "expanding earth" hypothesis, you may not post such again without express moderator permission.

Reality Check
2017-Apr-18, 09:59 PM
Plate tectonics with the old theory of a fixed size Earth is something of the past unless someone can prove the subduction zones between the ocean ridges as seen in https://www.universetoday.com/131459/mid-atlantic-ridge/.
The scientific evidence is that subduction zones (https://en.wikipedia.org/wiki/Subduction) exist between the measured ocean ridges. From the blog you linked to: What is a Subduction Zone? (https://www.universetoday.com/43822/subduction-zone/)

Subduction zones have key characteristics that help geologist and seismologist identify them. The first is mountain formation. Subduction zones always have mountain ranges caused by plate subduction. The next is volcanic activity as a plate is subducted the pressure and heat turns it into magma. These pockets of magma find paths to the surface and create volcanoes. A good example is the subduction zone near Chile. The final sign is deep marine trenches. These are the best evidence of a subduction zone as they are visible evidence of the crease formed by subduction of a plate. The most famous is the Mariana Trench.
And then there is common sense - we see that the ocean ridges are being continuously formed by volcanic activity, we see material flowing away from them (e.g. magnetic stripes in the sea floor), so where does this material end up?

grant hutchison
2017-Apr-19, 11:19 AM
There's a useful blog post here (https://clasticdetritus.com/2008/11/14/subduction-denialism-part-2-subduction-zones-trenches-and-accretionary-complexes/) (the second of a three-part series) which discusses and illustrates the evidence for subduction zones.

Grant Hutchison

grant hutchison
2017-Apr-19, 11:28 AM
If Silver and Behn (http://science.sciencemag.org/content/319/5859/85) are right (and they have been criticized), tectonics is in any case an intermittent process, and has already stopped for a while a billion years ago when the supercontinent Rodinia was formed.

Grant Hutchison

geonuc
2017-Apr-19, 11:44 AM
There's a useful blog post here (https://clasticdetritus.com/2008/11/14/subduction-denialism-part-2-subduction-zones-trenches-and-accretionary-complexes/) (the second of a three-part series) which discusses and illustrates the evidence for subduction zones.

Grant Hutchison

Indeed. That's an excellent blog.

publiusr
2017-Apr-29, 07:52 PM
I love the "Playground example of gravity-driven deformation" from that site.

If the Sun doesn't quite destroy the earth--it may actually recharge the plate tectonics. Neo-Hadean style.