Geologists call thissupercontinentPangaea, which means “all lands” in Greek. Studies of rocks discovered inancientareas of North America have revealed that the oldest recognized pieces of the continents started to type nearly 4 billion years ago, soon after Earth itself formed. Scientiststheorizethat this materials built up along the boundaries of tectonic plates during a course of calledsubduction. During subduction, plates collide, and the sting of one plate slides beneath the edge of one other. The crust and the top portion of the mantle form arigidshell around the earth that’s broken up into large sections known as tectonic plates.