<human>:  Can you explain the history of plate tectonics?
<bot>: Plate tectonics is the scientific theory that explains the movements of the Earth’s lithosphere, which is the outermost layer of the planet’s structure. It involves the breakup and interaction of the Earth’s crustal plates and the geologic activity that occurs at the boundaries between them. The origins of the theory can be traced to the late nineteenth century, when a German scientist named Alfred Wegener proposed the controversial theory of continental drift. This theory proposed that the continents had once been joined together in a single landmass, which he called Pangaea, but had since drifted apart and formed the continents as we know them today. His theory was refuted at the time but in the mid-twentieth century, it was proven that the Earth’s lithosphere is made up of several tectonic plates that are continually shifting, spreading apart, or coming together. An American geologist named Harry Hess first used the term 'plate tectonics' in the 1960s to describe the large-scale movements of the Earth’s tectonic plates. Since then, scientists have been able to better measure and understand these movements and their effects on the geologic activity of the Earth’s surface.