Volcanoes, Its Eruption, Types, Geographical Distribution & Products

VOLCANOES

The word volcano comes from the Greek work Vulcan which means god of fire. A

volcano is an opening in the surface of the Earth through which magma (molten

rock), gases and ash erupt.

Magma is molten rock within the Earth's crust. When magma erupts through the

earth's surface it is called lava. Lava can be thick and slow-moving or thin and

fast-moving. On Earth there are about 500 active volcanoes. About 75% of all

active volcanoes are situated in what is called the Pacific Ring of Fire

There are three main types of volcanoes:

1. Shield volcanoes

2. Strato-volcanoes

3. Cinder cones

1. Shield volcanoes

Shield volcanoes are low in height and are broad.

2. Stratovolcanoes

Stratovolcanoes are composed of alternating layers of lava and pyroclastic

material.

3. Cinder cone

A cinder cone is a cone shaped hill that is composed mostly of cinder-sized

pyroclastics.

http://miningmuet.webs.com Izhar Mithal Jiskani

1

Volcanoes, Its Eruption, Types, Geographical Distribution & Products

Volcanic Eruption

When magma is erupted or ejected from earth it is known as eruption. Magma is

known as lava when it reaches on earth’s surface. Lava is sticky, hard (when

cooled) and has the temperature of 2012OF, contains mostly steam with carbon

dioxide, nitrogen, sulphur-dioxide. Volcanoes are described as extinct, dormant, or

active.

1. An extinct (dead) volcano is one that is not erupting and is not likely to

erupt in the future.

2. A dormant (sleeping) volcano is one that is currently inactive, but has

erupted within historic times and is likely to do so in the future.

3. An active volcano is one that erupted recently.

Volcanic eruptions may be violent (aggressive/cruel) or mild (gentle). When

volcanoes are born in the sea, the eruptions may be more violent than those on

land because of the contact between the molten rock and water. Earthquakes,

lightning, tsunamis, and strong whirlwinds have been known to result from

volcanic eruptions. Mild eruptions occur when molten rock pushes through long

cracks in the Earth's crust and floods the surrounding areas.

Geographical Distribution or Location

Thousand of volcanoes scattered on the surface of earth but most active volcanoes

are present on two belts.

1. Major belt: Also called fire belt which is encircling the Pacific Ocean.

There are about 850 most active volcanoes.

2. Short Belt: this belt starts from Sol man Island through New Guinea and

Indonesia. There are about 200 most active volcanoes.

http://miningmuet.webs.com Izhar Mithal Jiskani

2

Volcanoes, Its Eruption, Types, Geographical Distribution & Products

Products

1. Solid: All the material comes out from a volcano in solid known as

Pyroclastic material.

2. Volcanic Bombs: A lava fragment that is ejected while viscous (partially

molten) and larger than 64 mm (2.6 in) in diameter

3. Cinder: When size of fragment is more than in diameter.

4. Ash or Dust: When fragment size is less than in diameter.

http://miningmuet.webs.com Izhar Mithal Jiskani

3