Volcanoes

Introduction

The volcano is an important natural hazard.
It causes great damage to life and property.
The volcano is a vent or opening, through which heated materials consisting of gases, hot water, lava, and fragments of rocks are ejected from the interior of the earth.
The passage of the earth’s crust through which magma and other volcanic materials are ejected is called the vent.
The funnel-shaped hollow at the top of the cone of a volcano is called a crater.
The scientific study of volcanoes is called volcanology.
Materials that come when volcanoes take place are called pyroclastic materials.

Causes for volcanoes

The temperature inside the earth increases with increasing depth (1° C per 32m)
Formation of magma because of increased temperature and pressure reduction.
Gases and water vapor are formed due to underground water heating.
Movement and breaking of major and minor plates of the earth.
Ascent of magma forced by excess pressure

Types of volcanoes

1. Active volcanoes

Volcanoes that constantly eject solid, liquid and gaseous materials are called active volcanoes.

Example:

Mt Etna and Stromboli of Italy.
St Helens of USA
Mauna loa and Mauna Kea of the Hawaiian islands
Pinatubo of Philippines , Cotopaxi and Chimborazo of Ecuador
Izalco of El Salvador

Facts to be remembered

Stromboli is known as a lighthouse of the Mediterranean
Izalco is called the lighthouse of central America

2. Dormant volcanoes

These volcanoes become quiet after the eruption but erupt after a long period of time.

Example:

- Mt Fujiyama of Japan
- Mt Krakatau of Indonesia.
- Mt Vesuvius of Italy

Facts

Mt Vesuvius, Mt Krakatau, and Mt. Pelean Volcanoes are called super Volcanoes.

3. Extinct volcanoes

The volcanoes have not been active for a considerable period of time.

These are called dead volcanoes.

Example:

Narcondum ( Andaman and Nicobar islands of India).

Barren islands of Andaman and Nicobar islands are important volcanoes in our country. It is an Active volcano.

Volcanic materials

The three types of materials ejected from the volcanoes.

A. Liquid materials

Lava is the most important liquid material ejected by volcanoes.

There are two types of lava.

Acid lava: It has a high percentage of Silica.

Basic lava: It has a low percentage of Silica.

Magma: the molten material found below the earth’s surface

Lava: when molten material reaches the surface of the earth

B. Solid materials

Volcanic bombs, dust, pumice, scoria, volcanic ash, cinder and rock fragments.

C. Gases

Sulphur, hydrogen, and carbon dioxide.

Distribution of volcanoes

1. The Circum-Pacific belt

Also called as pacific ring of fire

It is found in the eastern part of New Zealand, New Guinea, Philippines, Japan, the western part of Alaska, the USA, Hawaiian islands,

This belt experiences a greater number of volcanoes.

2. Midcontinental belt

Found in Alpines, the Mediterranean region, Europe, North Africa Etc.

3. Mid – Atlantic belt

This belt is found in the Mid-Atlantic Ridge, Iceland, etc

Effects of volcanoes

It can cause damage to life and property.
Volcanoes cause damage to agricultural fields, industries, dwelling roads, railways, airports, dams, reservoirs, etc.
It causes diversion of river course and flooding of water.
It can cause air pollution.
It can form rocks and minerals.

Volcanoes in Indian Regions

Barren Islands

SI NO	Volcanoes in India	Regions
1.	Barren Islands-	Andaman and Nicobar
2.	Deccan Traps	Maharashtra
3.	Narcodam	Andaman and Nicobar
4.	Bhar tang	Andaman and Nicobar
5.	Tosh am Hills	Haryana
6.	Dhoni Hills	Borders of Haryana and Rajasthan
7.	Dhinodhar Hills	Gujrat

Volcanoes

Introduction

The volcano is an important natural hazard.

It causes great damage to life and property.

The volcano is a vent or opening, through which heated materials consisting of gases, hot water, lava, and fragments of rocks are ejected from the interior of the earth.

The passage of the earth’s crust through which magma and other volcanic materials are ejected is called the vent.

The funnel-shaped hollow at the top of the cone of a volcano is called a crater.

The scientific study of volcanoes is called volcanology.

Materials that come when volcanoes take place are called pyroclastic materials.

Causes for volcanoes

The temperature inside the earth increases with increasing depth (1° C per 32m)

Formation of magma because of increased temperature and pressure reduction.

Gases and water vapor are formed due to underground water heating.

Movement and breaking of major and minor plates of the earth.

Ascent of magma forced by excess pressure

Types of volcanoes

1. Active volcanoes

Volcanoes that constantly eject solid, liquid and gaseous materials are called active volcanoes.

Example:

Mt Etna and Stromboli of Italy.

St Helens of USA

Mauna loa and Mauna Kea of the Hawaiian islands

Pinatubo of Philippines , Cotopaxi and Chimborazo of Ecuador

Izalco of El Salvador

Facts to be remembered

Stromboli is known as a lighthouse of the Mediterranean

Izalco is called the lighthouse of central America

2. Dormant volcanoes

These volcanoes become quiet after the eruption but erupt after a long period of time.

Example:

Mt Fujiyama of Japan

Mt Krakatau of Indonesia.

Mt Vesuvius of Italy

Facts

Mt Vesuvius, Mt Krakatau, and Mt. Pelean Volcanoes are called super Volcanoes.

3. Extinct volcanoes

The volcanoes have not been active for a considerable period of time.

These are called dead volcanoes.

Example:

Narcondum ( Andaman and Nicobar islands of India).

Barren islands of Andaman and Nicobar islands are important volcanoes in our country. It is an Active volcano.

Volcanic materials

The three types of materials ejected from the volcanoes.

A. Liquid materials

Lava is the most important liquid material ejected by volcanoes.

There are two types of lava.

Acid lava: It has a high percentage of Silica.

Basic lava: It has a low percentage of Silica.

Magma: the molten material found below the earth’s surface

Lava: when molten material reaches the surface of the earth

B. Solid materials

Volcanic bombs, dust, pumice, scoria, volcanic ash, cinder and rock fragments.

C. Gases

Sulphur, hydrogen, and carbon dioxide.

Distribution of volcanoes

1. The Circum-Pacific belt

Also called as pacific ring of fire

It is found in the eastern part of New Zealand, New Guinea, Philippines, Japan, the western part of Alaska, the USA, Hawaiian islands,

This belt experiences a greater number of volcanoes.

2. Midcontinental belt

Found in Alpines, the Mediterranean region, Europe, North Africa Etc.

3. Mid – Atlantic belt

This belt is found in the Mid-Atlantic Ridge, Iceland, etc

Effects of volcanoes

It can cause damage to life and property.

Volcanoes cause damage to agricultural fields, industries, dwelling roads, railways, airports, dams, reservoirs, etc.

It causes diversion of river course and flooding of water.

It can cause air pollution.

It can form rocks and minerals.

Volcanoes in Indian Regions

Barren Islands

SI NO

Volcanoes in India

Regions

1.

Barren Islands-

Andaman and Nicobar

2.

Deccan Traps

Maharashtra

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