Global tectonics, Indian Ocean. Satellite-based artwork of an Earth globe showing the tectonic boundaries (yellow lines) in the Indian Ocean. Seven primary tectonic plates make up the Earth's crust. Plates shown here include the African Plate, the Indian Plate, the Antarctic Plate and the Eurasian Plate. Phenomena observed at the plate boundaries include earthquakes, volcanic activity, mountain-building, and oceanic trench formation. The movement of the tectonic plates over the millions of years of geologic time drives the creation, destruction and drifting of the continents. The movement of the tectonic plates is thought to be driven by convection currents in the underlying mantle.