[Steve Van Doorn]

"(tectonic plates) are obviously 3-dimensional and the exact depth and deep boundaries and pretty much unknown"

My question is do they float on the magma? What keeps them from surging relative to the magma? Think of India and how it moved from South Africa to where it is.

[Repeal The 17th]

“...do they float on the magma...”
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That is the way I visualize them.
But huge thick chunks, not thin slivers.

[gundog]

I imagine it’s a matter of the planet’s rotation distributing mass equally, to the extent possible.