Continents move on upper mantle {continental drift}|. Upper-mantle asthenosphere and possibly all mantle has stable constant one-inch-per-year convection currents, caused by heat. Currents provide energy to move continents. Continents have been drifting for last 2,000,000,000 years. Six major and many minor crustal plates float on upper mantle.
Plate movements make crust slide, fold, and fault {diastrophism}.
Increased fluid pressure, changed electrical resistivity, decreased Earth natural electric currents, increased deep-well-water radon content, changed seismic-wave travel time, and seismicity affect crustal-plate movements {dilatancy}. Dilatancy models earth movements as inelastic swelling. Steady stress increase splits crust, allowing water flow. If water flows in slower than cracks open, crust splitting slows. Then water under pressure quickly fills crack, causing sudden slip. Changes from compression waves to shear waves cause seismic-wave travel-time changes.
Continents are 10% lighter than crust, and crust is 10% lighter than upper mantle, so continents float on crust, which floats on upper mantle {isostasy}.
Plate movements {tectonic process}| make crust slide, fold, and fault in diastrophism.
5-Earth Science-Planet-Plate Tectonics
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Date Modified: 2022.0225