The different ways in which tectonic plates rub against each other under the ocean or sea floor to create submarine earthquakes. The type of friction created may be due to the characteristic of the
geologic fault or the plate boundary as follows. Some of the main areas of large tsunami-producing submarine earthquakes are the Pacific
Ring of Fire and the
Great Sumatran fault.
Convergent plate boundary The older, and denser plate moves below the lighter plate. The further down it moves, the hotter it becomes, until finally melting altogether at the
asthenosphere and inner mantle and the crust is actually destroyed. The location where the two
oceanic plates
actually meet become deeper and deeper creating
trenches with each successive action. There is an interplay of various densities of
lithosphere rock,
asthenosphere magma, cooling ocean water and plate movement for example the Pacific Ring of Fire. Therefore, the site of the sub
oceanic trench will be a site of submarine earthquakes; for example the
Mariana Trench,
Puerto Rico Trench, and the
volcanic arc along the
Great Sumatran fault.
Transform plate boundary A transform-fault boundary, or simply a
transform boundary is where two plates will slide past each other, and the irregular pattern of their edges may catch on each other. The lithosphere is neither added to from the asthenosphere nor is it destroyed as in convergent plate action. For example, along the
San Andreas Fault strike-slip fault zone, the
Pacific plate has been moving along at about 5 cm/yr in a northwesterly direction, whereas the
North American plate is moving south-easterly.
Divergent plate boundary Rising convection currents occur where two plates are moving away from each other. In the
gap, thus produced hot magma rises up, meets the cooler sea water, cools, and solidifies, attaching to either or both tectonic plate edges creating an
oceanic spreading ridge. When the fissure again appears, again magma will rise up, and form new lithosphere crust. If the weakness between the two plates allows the heat and pressure of the asthenosphere to build over a large amount of time, a large quantity of magma will be released pushing up on the plate edges and the magma will solidify under the newly raised plate edges, see formation of a
submarine volcano. If the fissure is able to come apart because of the two plates moving apart, in a sudden movement, an earthquake tremor may be felt for example at the
Mid-Atlantic Ridge between North America and Africa. ==List of major submarine earthquakes==