Types of Volcanoes

There are about four main types of volcanoes. They are the ash and cinder volcano, the shield volcano, the dome volcano and the composite volcano.

An ash and cinder volcano is a steep-sided conical volcano formed from red-hot ash and cinders. The pyroclasts, which are thrown out, drop back around the vent. These pyroclasts slowly accumulate to form a cone made up of ash and cinders. The volcano grows rapidly but is not high and they are found in groups. One example is Parícutin in Mexico.

Shield volcanoes have gently sloping sides. They are formed by fluid basic lava, which flows for a distance before solidifying. There is no violent eruption. The volcano is low, broad and dome-shaped. Hot spot volcanoes are also shield volcanoes. Hot spot volcanoes are formed when a rising magma plume (rising columns of magma that originate from fixed locations within the mantle) melts a hole in the plate and rises through the vent to form a shield volcano. One example is the Mauna Loa in Hawaii.

Acid lava(dome) volcanoes are formed when viscous acid lava solidifies quickly to form a volcano with steep convex sides. An example is Mount Pelée in Martinique, West Indies.

Composite volcanoes, also called stratovolcanoes, are the highest and most common volcanoes. They consist of alternate layers of ash and cinders, and viscous acid lava. They are more steeper towards the top then the bottom. The viscous lava solidifies quickly, preventing magma and gases from rising and building up tremendous pressure. When the pressure cannot be suppressed, there will be an initial violent eruption of ash and cinders. The lava escapes and flows. Before long, the lava would solidify in the central pipe again. Repeated violent explosions of ash, cinders and lava build up a composite volcano. Lava also flows out of the volcano via secondary pipes to form secondary cones or conelets. An example is Mount Merapi in Central Java.

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