Plate Tectonics?

Question

Let's see... I'm gathering information to attempt writing a sci-fi story in a not-so-near, and most probably quite-distant future. I need some help with a few aspects of plate tectonics.

So, I understand plate tectonics are driven by the planet's internal heat (Part of it residual from original accretion and part derived from decay of radiactive material)

I also read somewhere that deep surface water is needed as a lubricant of sorts.

Now, I believe size is a constrain too. Small planets can't support active tectonics (I'm not sure about this and correct me if I'm wrong)

Now, if I am right on the statement above... Is there an estimate on how big is "big enough"? What do we need to make it work, mass, volume or both?

Answer 1

Water doesn't act as a "lubricant" as much as it facilitates melting. What does "lubricate" plate motion is the asthenosphere. It is a partially molten layer that the lithosphere sits above. For the purposes of your project, a Google search maybe sufficient to fill in your gaps.

Plate tectonics is driven by the "convection" of the mantle. This happens a little differently and MUCH slower than normal "pot of water" convection. But it is driven by hotter mantle near the core rising and cooler mantle near the crust sinking.

I will have to admit that in my planetary class size constraints were not brought out, but then we were just focusing on Venus, Earth, and Mars.

Answer 2

if you're trying to write a science fiction story, you should just use your imagination and create your own planetoid with lava flow it you want.
actually, scientist have found that the moon had once had lava flow. jupiter's moon Io still has lava flow.
if your chasing facts, density is important, as is mass. you are right about size. size determines how fast the planet cools down which will lead to the planet's plate activeness to stop.
sorry about the uncapitalized words. sorry. really sorry.