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