Volcanoes & its Types - Civil Services Preparation Online! UPSC & IAS Study Material

Volcanoes & its Types

by Devender

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The volcanic activities are connected with crustal disturbances and closely related with regions that have been intensely folded or faulted.

Volcanoes

Volcanoes are sudden & abrupt explosions in the earth's crust from which Magma, gases, dust, smoke & solid material burst out.

  • Magma while coming out can cool & solidify within crust as Plutonic rocks that result in intrusive landforms
  • Magma that reaches the earth surface, gets solidify and forms extrusive landforms

  • Sills & Dikes (Common intrusive landforms):
  • When an intrusion of molten magma is made horizontally along the bedding planes of sedimentary rocks, the resultant intrusion is called a Sill.

    Similarly, an intrusion when injected vertically as narrow walls of igneous rocks within the sedimentary layers is called Dike.

    Igneous intrusions on a larger scale are various types of Liths such as Laccoliths, Lopoliths, Phacoliths & Batholiths.

  • Laccoliths: An igneous mound with a dome-shaped upper surface & a level base, fed by a pipe-like conduit from below
  • Lopolith: An igneous intrusion with a saucer shape
  • Phacolith: A lens-shaped mass of igneous rock occupying the crest of an anticline or the bottom of a syncline & being fed by a conduit from beneath
  • Batholith: A large emplacement of igneous intrusive rock, mainly granite, that forms from cooled magma deep in the Earth’s crust

  • Extrusive Landforms:
  • The lava or molten magma gets out with very high pressure through a pipe known as Volcano’s neck or vent. The top portion of the volcano is known as a crater and when rainwater gets accumulated in, a crater lake is formed.

  • Some volcanos have greatly enlarged pits like cauldron which are known as Calderas
  • The dust and ash that come out of a volcano travels around the world and falls as black snow which has the tendency to bury houses & people
  • The coarser fragmental rocks are together known as Pyroclasts which include cinders, pumice & volcanic bombs

  • Types of Volcanoes

    There are basically three types of volcanoes namely:

  • Active Volcano
  • Dormant Volcano
  • Extinct Volcano
  • 1 Active Volcano:

    Active volcanoes are those that keep on ejecting volcanic material at frequent intervals.

    For example - Etna (Italy), Stromboli (Sicily – largest island in the Mediterranean Sea, near Italy), and Mt Stromboli (Lighthouse of the Mediterranean)

    2 Dormant Volcano:

    Dormant volcanoes are those that have not erupted for a long time but eruptions can occur any time in the future.

    For example - Barren Island (Andaman), Versuris (Italy)

    3 Extinct Volcano:

    These are those volcanoes that have had no eruption for a long time and even the possibility of eruption is also not much. However, we can never be sure about them.

    For example - Mt. Popa (Myanmar)

    Vesuvius (Bay of Naples near Italy) & Mt. Krakatau (Sunda straits b/w Java & Sumatra) were thought to be extinct but both erupted violently.


  • Distribution of Volcanoes in the world:
  • There are mainly three volcanic belts, however, there are many volcanoes that are outside these belts.

  • Circum-Pacific belt - It is known as the Ring of fire and it has around 2/3rd of the world's Volcanoes
  • Mid-Continental belt - It has various volcanoes of the Alpine mountain chain, Mediterranean Sea
  • Mid-Atlantic belt - It includes the volcanoes of the Mid-Atlantic Ridge

  • Geysers:
  • Geysers are hot springs characterized by intermittent discharge of water and steam into the air. This phenomenon is associated with a volcanic region where the water below gets heated beyond its boiling point.

  • It is often triggered by the gases coming out of the heated rocks
  • The world's best-known geyser is old faithful in Yellowstone National park, Wyoming
  • For Example: - Iceland, New Zealand, & Yellowstone park of USA


  • Hot springs:
  • Hot springs are springs that are produced by the emergence of geothermally heated groundwater from the Earth's crust.

  • These are more common than geysers
  • The water of hot springs rise to the surface without any explosion
  • These springs contain minerals that are of medical uses

For example - Iceland, Japan & Hawaii



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