Study of mid-ocean ridges led geologists to formulate the theory of plate tectonics. They hypothesized that Earth’s crust was divided into multiple plates, each containing a portion of ocean continent, or both and floating freely atop the liquid magma of Earth’s interior. Where two oceanic plates moved away from one another, magma rose to the surface, forming new earth. Where two continental plates collided, they crumpled and pushed each other upwards to build the planet’s great mountain ranges. Plate tectonics became the foundational principle in the field of geology, and it also confirmed Wegener’s theory of continental drift, demonstrating the mechanism by which landmasses move. Geologists now believe Pangaea was simply the latest in a long progression of supercontinents that have formed and split, a process that will continue through future eons.