South Carolina's quakes are located within a plate rather than at a plate boundary. The cause of earthquakes in South Carolina is not so clear. These quakes often are the ones that are the most destructive and well understood in terms of plate tectonics. The majority of earthquakes worldwide occur at plate boundaries when plates stick and then jump past each other. Plates move mere inches annually, carrying the continents and ocean basins with them as they drift about. The Earth's heat drives convection currents in the asthenosphere, moving the plates past one another very slowly. The crust (lithosphere) is broken into about 12 enormous plates that float on hotter, softer rocks in the underlying mantle (asthenosphere). Today, most people accept the theory that the Earth's crust is on the move, and we call this theory plate tectonics. Continental drift is based on the idea that the continents bumped into, and slid over and under each other and at some later time broke apart.
Plate tectonicsįor hundreds of millions of years, the forces of continental drift have reshaped the Earth. The force that causes the stress within the rock is a result of movement of giant sections of the Earth's crust (see Figures 6 and 7). The land around a fault may shift horizontally, vertically, or a combination of these motions (see Figure 5).
Rocks respond to stress (squeezed or pulled apart) near the Earth's surface by breaking, and when rocks move along either side of a fracture, it is called a fault. An earthquake is the violent shaking of the Earth caused by a sudden movement of rock beneath its surface.
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