Draining the Oceans and Tectonic Plates

	Draining the oceans reveals that the Earth's solid surface -- its crust -- is divided into highlands and lowlands. The highlands are the landmasses that form the continents and the lowlands form the ocean basins. Things to notice: The ocean floor has mountain chains, isolated peaks, and deep valleys. The pronounced ridge in the middle of the Atlantic ocean marks the location of the Mid-Atlantic Ridge where new seafloor is being created by magma rising from the mantle. Thus, the Atlantic is getting bigger with time. The Mid-Atlantic Ridge, is also visible in the Tectonic Plates dataset.
	The Earth's crust is not a fixed, continuous shell. It is broken into a mosaic of moving plates. As these plates move and shift against one another they release enormous amounts of energy in the form of earthquakes. Things to notice: The boundary between the Pacific plate and the North American plate is located along the coast of California. The movement or slip of the two plates past one another has created the San Andreas fault, the source of many earthquakes.
	This sequence shows the locations of strong earthquakes worldwide. Things to notice: Earthquakes tend to be concentrated at the boundaries of Earth's plates. Volcanoes are also more frequent along the plate boundaries.
	As oceanic plates are driven under continental plates, forcing them into the mantle, they begin to melt. This produces molten rock, which rises to the surface forming volcanoes. The locations of volcanoes which erupted between 1960 and 1995 are shown. Things to notice: Like earthquakes, volcanoes are concentrated along boundaries between Earth's plates
Next: The Biosphere