definition+of+a+volcano


 * __ Definition Of A Volcano __**

 A volcano is basically an opening in the planets crust, which allows hot __[|magma]__, ash and gases to escape from below the surface of the earth. All volcanoes come in different shapes and sizes. Although all volcanoes are made from hot magma reaching the surface and erupting, there are are four main types of volcanoes on Earth. They are Shield volcanoes, Stratovolcanoes, Cinder Cone volcanoes and Dome volcanoes.

__Shield Volcanoes__ __[|Shield volcanoes]__ have lava flows with low viscosity. This lava flows dozens of kilometres and spreads widely before cooling and hardening. Shield volcanoes are very wide and have smooth, sloping sides. Lava flows that have built up over time form the layers of the flanks of the volcano. __Stratovolcanoes__ __[|Stratovolcanoes]__ are composed of several kinds of lava and bodies of igneous rock are formed when former channels of magma have cooled. The eruptions of rock and ash grow to gigantic heights.  Stratovolcanoes are also known as Composite volcanoes.

__Cinder cone Volcanoes __ __[|Cinder cone volcanoes]__ are often smaller, and come from short lived eruptions. These volcanoes are only about 400 metres high. Cinder cone volcanoes are made up of layers which are made up of heavier rocks near the vent, and ash towards the edges.

__Dome Volcanoes __ The shape of the Dome volcano is formed by thick lava that cools and hardens rapidly. Lava flows that have built up over time create the round shape of the Dome volcano. This volcano is short and round.

__**Volcanoes Can Spark Lightning**__

Volcanic eruptions can spark lightning. Physicists have long been confused as to why sand grains and other small particles can build up electrical charges as they collide with one another, sometimes discharging lightning in dust storms or plumes of volcanic ash. As some of my photos show of eruptions which have sparked lightning storms, they create terrible but awesome views.

__**Volcanic Activity**__

 Volcanoes are either active, dormant or extinct. __[|Active volcanoes]__ have erupted in the last few thousand years. A __[|dormant volcano]__ is one that isn’t currently erupting or active, but geologists think that it is possible that it might erupt. An __[|extinct volcano]__ is one that is not expected to erupt again by scientists.

__**Volcanic Ash**__

Volcanic ash is made up of small tephra which are bits of pulverised rock and glass created by volcanic eruptions. Significant accumulations of ashfall can lead to the immediate destruction of most of the local ecosystem, and even the collapse of roofs on man made buildings like houses. Over a period of time ashfall can lead to the creation of fertile soils ideal for farming.

__**Magma or Lava?**__

You may or may not know the difference between lava and magma. Magma is inside the volcano before it has erupted out of the opening of the volcano. Lava however is magma that has come out of the volcano and has started to flow down the sides of the volcano.

Mount Vesuvius is one of the most famous volcanoes on Earth. When it erupted in Italy in 79AD, it made history as the world's most famous eruption. It destroyed three towns that lived near the volcano. These towns were Herculaneum, Pompeii and Stabiae. Stromboli is also a famous volcano that resides in the Mediterranean Sea. This volcano has been active since ancient times. It erupts during long periods of time, months, or even years at a time. There are even extraterrestrial volcanoes. Volcanoes are not limited to the world. They appear all over the solar system. A famous volcanic mountain on mars is Olympus Mons. It is one of the tallest mountains in the Solar System and is twice the height of mount Everest. This volcano is a shield volcano. Olympus Mons translates to Mount Olympus.
 * __Famous Volcanoes on the Earth and Beyond.__ **




 * __References__**

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