What Causes Tsunamis
Volcanoes are those mountains from which hot magma about 1500 degree centigrade in temperature flows out containing silica compounds and gases.
Some volcanoes flow out with smooth gentle moving lava while other erupts vertically upwards with fragmented pyroclastic material containing lots of gases.
There are three types of volcanic magma; Basaltic, Andesite and Rhyolite with 50, 60 and 70% silica composition respectively.
As silica concentration increases, the fluid becomes more viscous.
Rhyolite, being viscous in nature, hinders the leakage of underlying gases escaping into environment, till the pressure increases to such an extent, which tends to explode out magma outbursts.
Basaltic volcanoes, on the other hand, being low in silica and gas particles, flow smoothly.
Majority of Earth’s volcanoes reside on the plate tectonic boundaries. Plate tectonics are Earth crusts’ layers, which move relative to each other often colliding in the process.
There are three places where volcanoes form:
The first being divergent plate boundary is the place where two pieces of lands rips apart, creating a hollow in between, from which hot mantle comes out. These areas, in general, outflow basaltic lava. Mount Erta Elae in Ethopia is one such example. Underneath the mount, lies the African plate boundaries moving apart
Also Read: What causes Tsunami?
The second is the convergent boundary or subduction zone, in which oceanic plate being denser than continental plate moves underneath the latter. The oceanic plate, while subducting down, reaches the hot mantle region where it liquefies into hot fluid.
Later on, the fluid, composing high gaseous content due to oceanic influence, erupts above the earth crust in a pyroclastic fashion. A typical example is the North American plate beneath which subducts Juan de Fuca, an oceanic plate.
Continent to continent convergent boundaries do not form volcanoes, as the two bulky plates building and squashing one other, narrows the lava passing channel leading from the mantle up to outlet.
The third is the hot spot phenomenon which, unlike other, is not located on plate boundaries. Instead, It is a hot mantle vent which exists underneath the mid of a tectonic plate. It makes its way vertically up to the crust through an intermediate geologically moving plate. The Hawaiian island are the classic examples of hot spots volcanism and the magma fluid escaping out of it, flow as gentle moving lava.