Are volcanoes formed from earthquakes?

Question

I know that some earthquakes are caused by volcanoes and that some earthquakes can trigger volcanic eruptions close to where the earthquake is.\n\nBut what if a great earthquake(8.0 or above) occurs and causes there to be a fault line? If more earthquakes of any magnitude occur in the same area the fault line would get deeper and deeper until the mantle is exposed. Then the pressure in the mantle is released and lava starts flowing out of the fault line. Over years this would form a ridge whether that is underwater or inland. \n\nBut are any volcanoes actually formed from earthquakes?

Answer 1

Earthquakes themselves do not form volcanoes, however, the tectonic forces in which the earthquakes derived from may ultimately produce a volcano or magmatic arc. For example, intercontinental rifting creates extensional forces and "thins" out the crust. During this process you develop a system of listric normal faults (or a horse and graben topography like the Basin and Range Province). The force of the crust pulling apart will induce earthquakes in addition to the accent of magma through deep fissures or conduits. Earthquakes and volcanoes are both side effects of tectonic stresses but one does not cause the other. Your idea of a continuous fault line that gradually gets "deeper" is essentially what is called rifting. An example would be the Rio Grand Rift. Rather than just the fault line getting deeper, it is actually the crust itself getting thinner to allow the mantle to reach the surface. This is when you get flood basalts. Another example would be within compression tectonic regimes, where you might have an oceanic plate subducting beneath continental crust (i.e. west coast) and developing a magmatic arc. The compressional forces from subduction will also create significance earthquakes, however, those earthquakes do not produce the volcanoes. A fault line will also not reach the mantle due to the brittle ductile transition zone. Once you reach a certain depth, the ductile state of the earth will not be able to produce the stress and frictional needed to produce an earthquake. The majority of the large earthquakes that produce the most damage come from surface waves that derived from a release in tension from fault lines that were fairly shallow.