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Plate Tectonic Theory
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Plate Tectonic Theory
Evidence Mind Map
Divergent Plates
Divergent plates are tectonic plates that move away from each other. This includes mid-ocean ridges and the sea floor spreading theory, deep ocean trenches and rift valleys.
Sea Floor Spreading
Mid-Ocean Ridges + Sea Floor Spreading
Mid-Ocean Ridges
Sea floor spreading occurs in mid-ocean ridges, and is the process of two oceanic plates moving away from each other. Hot magma below the earths crust undergos convection currents, where hot magma gains heat energy, loses density and rises, before losing heat energy, increasing density and sinking back to the heat source. When two oceanic plates pull apart and distance between the two plates increases, some hot magma will gain enough heat energy and lose enough density to rise to the apex of the ridge, cool down and form new rock layers on each of the plates.
Evidence
The sea floor spreading theory was determined by absolute radiometric age dating. This studied the radiation of oceanic plate rock and found that the rock at the apex of two oceanic plates was expressing large amounts of radiation. However, rock at a greater distance from the apex was not expressing as much radiation, and from this, it was suggested that the rock at the apex of a mid pcean ridge was new.
Rift Valleys
Continental Drift
Natural Disasters
Natural disasters can be a result of convergent (plates moving towards each other), divergent (plates moving away from each other) or transform plates (plates sliding along each other). Earthquakes are often a result of any plate movement, tsunamis are a result of oceanic plate movement that displaces water, and volcanic eruptions can be a result of plate movement and magma pressure.
Geological Events
From divergent plate boundaries, mid ocean ridges can be created