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So here's the picture, an island about the size of Sicily is on its own tectonic plate, it borders three other tectonic plates, it's separating from all of them at the exact same time. This is a fantasy setting but I don't want "because magic" to be the only answer, so please tell me if this is scientifically possible. To clarify, plates directly neighboring the small plate are moving away from the small plate, at the same time the small plate is scrunching up.

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    $\begingroup$ do you mean the outer plates are all moving inward making the central plate smaller, or are the outer plates fixed (or moving away) with the inner plate shrinking? $\endgroup$ – Josh King Mar 13 '18 at 19:44
  • $\begingroup$ what is between the island plate and the plates that are moving away? $\endgroup$ – Willk Mar 13 '18 at 19:51
  • $\begingroup$ I just edited the question, based on your comment to Alexander's answer. If the new text is incorrect, please revert it. Otherwise, you'll know why I thought that "all the plates" meant... all the plates. $\endgroup$ – RonJohn Mar 13 '18 at 21:00
  • $\begingroup$ I didn't revert, I just had to reword the question Abit more to give a better picture. $\endgroup$ – skout Mar 13 '18 at 21:43
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Not in the sense that you may be thinking.

You may be thinking of something like our own Antarctic plate, for example. It is subducting somewhat beneath South America, but other than that, the whole of its boundaries are either transform or, specially, divergent faults - which means that overall, its movement away from other plates (from its point of view) is much larger than its movement towards South America.

A divergent boundary happens when plates are moving away from each other. However, this does not mean that the plates are actually separating. They grow bigger around their boundaries. This will not expose mantle. According to the wiki on divergent boundaries:

Divergent boundaries within continents initially produce rifts which eventually become rift valleys. Most active divergent plate boundaries occur between oceanic plates and exist as mid-oceanic ridges (...)

... Which might be the dominant feature on the seafloor around your island. It will probably be surrounded by ocean ridges which are sure to have hydrothermal vents.

But your tectonic plate will always keep the same distance from the other plates.

I have edited the answer to include Jaycie's comment:

The Antarctic Plate is that the plates surrounding it are moving away from it from its point of view. This way of describing plate motion, as relative to another plate, is pretty standard. From the point of view of the African Plate, Antarctica is moving toward the Pacific Plate but the Pacific Plate is moving in a similar direction roughly twice as fast, so Antarctica can't catch up.

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    $\begingroup$ The only thing I would add about the Antarctic Plate is that the plates surrounding it are moving away from it from its point of view. This way of describing plate motion, as relative to another plate, is pretty standard. From the point of view of the African Plate, Antarctica is moving toward the Pacific Plate but the Pacific Plate is moving in a similar direction roughly twice as fast, so Antarctica can't catch up. So skout's plates don't necessarily imply that the Sicilian Island one is stationary, just that that surrounding plates are moving away from it from its point of view. $\endgroup$ – KernelOfChaos Mar 13 '18 at 21:35
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    $\begingroup$ @JaycieBeveri good point. I'm adding it. $\endgroup$ – Renan Mar 13 '18 at 21:37
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Define "separating".

Growing smaller somehow so it pulls away from the surrounding plates?

Rising upward?

It a plate would begin to "shrink" somehow, the mantle of the Earth would be exposed, its top layer begin to cool, and form a new section of the Earth's crust. So too if a section of the crust rose upwards or simply vanished.

I expect that sudden exposure of the mantle would likely be quite violent - water on the surface would likely begin to spill into the exposed mantle, generating superheated steam.

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  • $\begingroup$ The steam wouldn't superheat. The water would touch exposed mantle, vaporize into steam, and the steam wouldn't continue to be heated by the exposed mantle. Anytime there is still liquid water being boiled, the steam won't superheat. $\endgroup$ – Samuel Mar 13 '18 at 20:42
  • $\begingroup$ True enough, I expect the massive expansion of said steam would be a far bigger threat than the heat anyway. $\endgroup$ – VBartilucci Mar 13 '18 at 20:44
  • $\begingroup$ Agreed. Regular 100°C steam is dangerous enough. $\endgroup$ – Samuel Mar 13 '18 at 20:45
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Yes, this is possible. Tectonic plates are moving in seemingly random patterns, colliding or separating from each other. When the plates collide, their boundary is called "convergent". When they are moving apart, they called "divergent" (not to be confused with popular YA series). Sometimes, the plates can be completely divergent, meaning that all their neighbors are moving away from them. The real world examples of such are East Africa and Iceland.

Tectonic Plates and Their Boundaries

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  • $\begingroup$ OP says "all the plates are moving away from each other". That means all the plates must be divergent, which is impossible. $\endgroup$ – RonJohn Mar 13 '18 at 20:12
  • $\begingroup$ @RonJohn I understand it that 3 plates are moving away from the central plate, not necessarily from all of their neighbors. $\endgroup$ – Alexander Mar 13 '18 at 20:29
  • $\begingroup$ @RonJohn I did not infer that the world Only had four tectonic plates, nor did the question encompass the whole world. It was talking about an island the size of Sicily and it's relation to the surrounding plates. $\endgroup$ – skout Mar 13 '18 at 20:37
  • $\begingroup$ @RonJohn Is it though? If you think of the three surrounding plates like the three leaves of a mechanical iris opening I don't think any natural laws are violated. Placing an additional small plate in the opening gap seems reasonable too. $\endgroup$ – Samuel Mar 13 '18 at 20:37
  • $\begingroup$ @Samuel his questions are ambiguous. $\endgroup$ – RonJohn Mar 13 '18 at 20:56

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