Poetic Empiricist's Plate Puzzles

Before the 1960’s they didn’t know,
what caused Earth to shake or volcanoes to blow.
A mechanism was found to implicate,
a wondrous process using moving plates.
In general, plates push out from a ridge formation,
a perpetual site of ocean crust creation.
On the multimillion year journey it was dealt,
just to be pulled in a trench, where it’ll sink and melt.
New rock feeds the cycle in its molten liquid state.
This stress affects the remaining rock of the plate.