Types Of Volcanoes

A volcano can be described as a rupture in earth's crust. Mostly found at the boundaries of earth’s convergent or divergent tectonic plates, volcanoes allow hot molten rock, gases and ash to escape from below the surface, during every eruption. Based on their structure, volcanoes are classified into three main types, with each of them being significantly different from the other. Browse through the following lines and explore some more information on the most common types of volcanoes.

Typically large in size, a shield volcano is characterized by shallow-sloping sides. Lava, of low viscosity, flows easily through this type of volcano. The constant flow of the fluid basaltic lava, from the fissures on its surface, gives rise to the build up of a huge volcanic mountain. As the volcanic emission "magma" reaches the surface, its viscosity varies, depending on its temperature and composition. Shield volcanoes are recorded to be the largest volcanoes on earth.

 

With its base under the ocean, Mauna Loa of Hawaii is the largest active shied volcano on earth. A number of shield volcanoes are situated in Hawaiian Islands as well. Due to their huge size, such volcanoes are sometimes referred to as mountain range. The temperature of the magma of shield volcanoes in Hawaiian Islands - 1200^o C - has been recorded to be the highest. The magma emitted by other continental volcanoes has relatively lower temperature, of about 850^o C.

One of the most common types of volcanoes, composite volcano is a tall conical structure. Also called strato volcano, it is characterized by the formation of a number of layers (strata), of hardened lava, volcanic ash and tephra, due to sequential outpourings of eruptive material. In this case, explosive volcanic eruptions occur periodically. Before spreading further, the viscous lava, flowing from a composite volcano, cools down and hardens. The lava is formed by magma and is often felsic.

 

Periodically though, composite volcanoes erupt in an explosive way. Its viscous magma, when it rises to the surface, clogs the crater pipe. As a result, the gas in the crater pipe is locked up, which gives rise to an explosive eruption. This type of volcanoes is mainly found to be based along the sub duction zones. Mount Hood, Mount Rainier, Mount Shasta, Mount Fugi, Mount Mayon and Vesuvius are counted amongst the popular composite volcanoes.

 

Another common type of volcanoes is the cinder cone volcano, also called scoria cone. The structure consists of a steep conical hill, of volcanic fragments. Cinder cone volcanoes are characterized by accumulation of volcanic fragments, around and downwind, from a volcanic vent. These rock fragments, known as cinders, contain a number of gas bubbles, "frozen" into place. The magma cools down quickly after exploding into the air, during an eruption. Cinder cone volcanoes can vary, from ten to hundreds of meters, in their height.

 

A number of cinder cone volcanoes seen on earth have bowl-shaped crater at the summit. Lava flows down the volcano on one side of the crater. It may also originate from a vent located on the flank of the volcano. Paricutin is a well known cinder cone volcano, which emerged out of a corn field in Mexico, in 1943, from a new vent. This type of volcano is mostly found on the flanks of shield volcanoes and composite volcanoes. Cerro Negro in Nicaragua has been recorded as the most active cinder cone volcano in the world, at present.