Ridge

drill the ocean floor. find the barcode that proved drift.

sample rock outward from a mid-ocean ridge — mirrored ages, mirrored magnetism

New seafloor is born at a mid-ocean ridge and pushed outward in both directions at a steady rate, so a rock’s age is just its distance from the ridge — plot age against distance from either side and it forms a mirrored V. Earth’s magnetic field also flips polarity every so often, and the still-molten rock freezes in whichever direction it points, so the seafloor records those flips as bands, mirrored the same way. Two independent measurements agreeing with each other, on both sides of every ridge on the planet, is what actually settled continental drift in the 1960s.

Concepts: geology, magnetism.

An interactive you play with one thumb, on Wundr.