What is the fastest rate plates can move?

Question

without being a bunch of dust, I mean.

So I'm working on this science fiction project and one of the planets has very fast tectonic plate movement, so it's uninhabitable, covered in magma, etc. What is the fastest rate the plates could move without it being completely ridiculous?

Earth's plates move about one inch per year. That's nothing! I want this planet to move a lot faster, but without the plates completely breaking apart into a bunch of dust or something.

Are there any planets discovered, not necessarily in our solar system, with relatively quick plate movement? If so, how fast? Tell me everything.

Answer 1

I think you have a Hollywood-esque perception regarding our knowledge of planets around other stars.  We've never even photographed the pale dot of a planet around other stars (we detect them by other means) let alone knowing if there is tectonic activity on their surfaces.

You might do better asking this over in the geology section.

Answer 2

We don't know very much about the planets that have been discovered outside our Solar System, apart from the fact that we believe they are there.

Plate tectonics happens on Earth because the planet is large enough that the core has remained molten. You could guess that any planet around the size of Earth could well have plate tectonics. Mars, for example, is much smaller than Earth and did used to have active vulcanism and perhaps plate tectonics in the distant past - billions of years ago. But because it is so much smaller, the core has cooled, and any tectonic activity has ceased.

Venus is only slightly smaller than Earth, but is a special case because of the massive pressure of its atmosphere.

But one of the moons of Jupiter - is it Io? - has active volcanoes because it is close to Jupiter and its huge magnetic field (remember that Jupiter is the biggest planet in the Solar System).

So for a planet in a hypothetical (or realistic fictional) Solar System to be massively tectonic, you could expect it to be a large rocky planet or moon, at least the size of Earth, perhaps orbiting close to a gas giant planet, or close enough to the star that the star's influence on it is great enough.

And remember that any planet with tectonics and volcanoes is likely to have a thick, perhaps poisonous, but at least stinky, atmosphere...

As to the rate of plate movement, the average may only be a matter of inches per year, but India has still managed to impact Asia fast enough (and consistently enough) to push up all the Himalayas, and to squeeze out South East Asia.

Speaking of India, the Deccan Traps are mountains created in a period of MASSIVE volcanic activity, which goes hand in hand with plate tectonics.

So don't be afraid of being ridiculous. Use a number that you feel is warranted, as long as you have good "scientific" or reasonable (at least) reasons to justify your decision.