- Volcano is the name derived from ‘Vulcano’, a volcanic island in Italy. A volcano is the rupture on the earth’s crust through which lava, ash and gases come out.
- Rocks below the earth’s crust become thick liquid known as magma due to high temperature. Eventually, magma forces through vent or fissures on earth’s surface. It erupts in the form of volcanoes or lava flow.
- Volcano consists of different parts like vent, magma chamber, volcanic cone, composite cone, crater, caldera, plug etc.
- The Volcanic Explosivity Index (VEI) is used to measure the volcanic eruption. It can be calculated on the basis of product volume and cloud height during the eruption.
- Volcanoes generally originate from convergent plate boundary, hot spot and, divergent plate boundary. Volcanoes can be classified into three categories on the basis of their frequency of eruption. These are active volcanoes, dormant volcanoes and, extinct volcanoes.
- Active volcanoes are the types of volcanoes that keep on erupting at regular intervals. Dormant volcanoes have erupted earlier and are supposed to erupt again in the future. Extinct volcanoes are not at all active and are unlikely to erupt in the future.
- The eruption of volcanoes becomes violent when volcano explodes after a long period, and suddenly pressure decreases from rising magma and gases start to expand. The shape of the volcano is determined by the components involved in lava. There are three major shapes of volcano. These are conical volcano, shield volcano and, fissure volcano.
- A conical volcano is characterised by the conical shape mountain with steep slopes. A shield volcano is formed when the lava flows quietly and spreads in a large area. It is build up slowly by the solidification of lava. Fissure Volcano is formed when the lava is solidified in long and narrow cracks.
- Eruption takes place through horizontal cracks in a fissure volcano. Different types of intrusive and extrusive landforms are formed by volcanoes.
- There are various features associated with volcanic regions. Some of these features are Crater Lake, bubbling mud pool, hot spring, volcanic plug and, geyser. A crater lake is formed when the caldera is filled with water. A bubbling mud pool is found in the area having high temperature with limited supply of water. Geyser erupts with the steam and water accumulated in the earth crust. Water heated by volcanic rocks comes to the surface as hot springs.
- Volcanic plugs are the remaining parts of the volcanic mountains, after their outer layer is eroded. Volcanic eruption can be destructive as well as constructive. The destructive influence of volcanic eruptions can be listed as loss of life and, loss of property. The constructive influences of volcanic eruptions are soil formation, source of precious stones, and use of hot springs for heating and supplying hot water to residential areas.
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Intrusive volcanic rocks are those which are formed ________________Marks:1
When cooling occurs within the crust
The lava that is released during volcanic eruptions on cooling develops into igneous rocks. The lava that cools within the crustal portions assumes different forms. These forms are called intrusive forms.
The Deccan trap is a large ___________Marks:1
Flood basalt province
The Deccan Traps from India, presently covering most of the Maharashtra plateau, are a much larger flood basalt province.
Hawaiian volcanoes are:Marks:1
Barring the basalt flows, the shield volcanoes are the largest of all the volcanoes on the earth. The Hawaiian volcanoes are the most famous examples of shield volcanoes.
Volcanoes are ___________Marks:1
A direct source of information about the interior of the earth
Volcanic eruptions are direct sources of information about the interior. As and when the molten material (magma) is thrown onto the surface of the earth, during volcanic eruption it becomes available for laboratory analysis.
Which type of volcanic eruptions has caused Deccan Trap formations?Marks:1
The Deccan Traps are a large igneous province and one of the largest volcanic features on Earth. They consist of multiple layers of solidified flood basalt that together are more than 2,000 m thick and cover an area of 500,000 km2 .