What happens at a plate boundary

Holderness loses metres of till each year; the Himalaya gain millimetres of rock. Both are plates doing different jobs at their edges.

Rocks bend or they break. Anticline, syncline, then the three fault slips.

Focus is in the rock. Epicentre is the map dot. P, then S, then the surface wave that does the damage in town.

Viscosity is the plot. Shield, strato, rift — three shapes from one slider.

Magnetic stripes are a tape recorder. New crust at the ridge, older away.

The Atlantic is opening. One day it will close. The Caledonides and the Appalachians are an older ocean that already did.

Scotland is still rising after the ice. Hudson Bay is still rising too. The crust floats. Load it, it sinks. Unload it, it comes back.