T Tectonic Earthquake: earthquake that occurs when the earth's crust breaks due to geological forces on rocks and adjoining plates that cause physical and chemical changes. Tectonics: large-scale deformation of the outer part of the Earth resulting from forces in the Earth. Tension: the stretching or extension of a material. Theory: a hypothetical entity or structure explaining or relating an observed set of facts. Time Series: a graph that shows receiver position, in three dimensions, over time, for each individual GPS site. Troposphere: found below the stratosphere, 7-10 miles from Earth's surface; area where clouds form, temperature changes, and convection is active.