Seafloor spreading is when continents drift apart, new ocean floor forms between them by this process. Subduction -- continents moving towards each other when the old ocean floor between them sinks back do(cid:449)(cid:374) i(cid:374)to the earth"s i(cid:374)terior. Plate tectonics when twenty distinct pieces (lithosphere), or plates, that slowly move relative to each other, in many ways divergent, convergent, subduction. For something to get a large earthquake, you must have rigid material. Many things give us evidence that earths continents were once just one big piece (pangea) Locations of past glaciations: as glaciers flow, they carry sediment grains of all sizes with them. The grains from the base of the moving ice carve scratches, called striations, into the substrate. When the ice melts, it leaves the sediment in a deposit called till: scientists study the age of glacial till deposits, they discovered that large areas of the land were covered by glaciers during time intervals.