How do shield volcanoes support/oppose the continental drift theory? Watch

username1373182
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Any help greatly appreciated.
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brainzistheword
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(Original post by abrack)
Any help greatly appreciated.
It's been a while since I did this but isn't it to do with the fact that the plates are moving away from each other (continental drift) which means that magma can rise up and as it erupts this produces its shape.

I believe this is asking the right lines but websites like bbc bitesize should offer a good explanation
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Leviathan1741
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I have a different take on this:

Though shield volcanoes can form over rift zones where the crust is pulling apart allowing magma to rise between them, many are formed over hotspots, which are fixed areas of high heat flow originating from the core-mantle boundary.

Taking the Hawaiian island chain as an example, the reason that there is a chain of islands and seamounts (rather than one huge shield volcano) which are older and more eroded with increasing distance from the hotspot, is because the Pacific plate is constantly moving, currently towards the north west. As the plate moves, it carries the active volcano above the hotshot away from the source of the magma, causing it to become extinct and allowing a new volcano to grow in its place.

This provides evidence that tectonic plates do move, supporting the continental drift theory
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hezzlington
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(Original post by Leviathan1741)
I have a different take on this:

Though shield volcanoes can form over rift zones where the crust is pulling apart allowing magma to rise between them, many are formed over hotspots, which are fixed areas of high heat flow originating from the core-mantle boundary.

Taking the Hawaiian island chain as an example, the reason that there is a chain of islands and seamounts (rather than one huge shield volcano) which are older and more eroded with increasing distance from the hotspot, is because the Pacific plate is constantly moving, currently towards the north west. As the plate moves, it carries the active volcano above the hotshot away from the source of the magma, causing it to become extinct and allowing a new volcano to grow in its place.

This provides evidence that tectonic plates do move, supporting the continental drift theory
I agree with everything in your post, however, we have to be careful not to confuse continental drift with plate tectonic theory.

Your brilliant explanation is evidence of plate tectonic theory.

I have not read the original papers that proposed continental drift (Wegener?), but I recall (perhaps incorrectly) that it didn't make the distinction between oceanic and continental crust, and predicted very high plate velocities. The mechanism behind the movement of the plates was incorrect, and was much better explained by plate tectonics.
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Bigbarlow180
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(Original post by hezzlington)
I agree with everything in your post, however, we have to be careful not to confuse continental drift with plate tectonic theory.

Your brilliant explanation is evidence of plate tectonic theory.

I have not read the original papers that proposed continental drift (Wegener?), but I recall (perhaps incorrectly) that it didn't make the distinction between oceanic and continental crust, and predicted very high plate velocities. The mechanism behind the movement of the plates was incorrect, and was much better explained by plate tectonics.
Yes, Wegener was the first to publish ideas surrounding the Continental Drift theory, but he lacked any sort of explanation of the mechanism behind the movements of the plates. The causal mechanism for the movement was first suggested by Holmes (1929) who gave the first explanation of convection currents.
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hezzlington
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(Original post by Bigbarlow180)
Yes, Wegener was the first to publish ideas surrounding the Continental Drift theory, but he lacked any sort of explanation of the mechanism behind the movements of the plates. The causal mechanism for the movement was first suggested by Holmes (1929) who gave the first explanation of convection currents.
I thought Wegener proposed that the break up was due to earth rotation? I'm not sure though! I haven't studied continental drift since first year of university, however I have studied plate tectonics, and convective cells are not the mechanism solely responsible for plate motion. Nonetheless, Holmes did fantastic work and convective cells driving plate motion was what I was taught at A level! I would however heck what the syllabus is for A level, and go according to that, even if it might not be the full story.
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