Introduction to Volcanic Mountains
Volcanic mountains are a special class of mountains. A volcano is a vent or opening through which magma, ash, gases, and water vapour are ejected out. Volcanic mountains consist of – Magma chamber, Vent, Lava, Crater, and pyroclastic flow.
Volcanic soil or the soil around a volcanic mountain is very fertile. This is because all the required nutrients come out with the volcanic eruption. Volcanic mountain or volcano may be active, dormant or extinct, based on the level of their activity.
Characteristics of a volcano or volcanic mountains
- A magma chamber is a hollow space inside the earth surface. The molten rocks are called magma. It is present just below the vent of the volcano and is a source of lava.
- Magma chamber contains molten rocks and gases under high pressure. Conduit is a pipe-like structure through which magma comes out and it opens into the main vent. The depth of the magma chamber is usually 1km to 10 km.
- Lava is the molten rock or magma that comes through a volcanic vent. It generally consists of silicates or silica rocks and is in liquid or semi-solid form. The temperature of lava is anywhere between 700 0 C to 12000
- Lava cools and hardens after coming into contact with the air. This cooled lava forms a volcanic mountain-like shape.
- A vent is a hole in the earth’s surface through which the lava comes out with great pressure. Generally vent is a weak point on the crust of the earth. There could be more than one vents of a volcanic mountain.
- Craters are the circular depressions around the main vent. Craters are developed due to a large explosion in the volcano. These are formed when the magma chamber is present near the vent.
- The volcano becomes active due to the creation of high pressure in the magma chamber. Generally, the magma chamber contains a large amount of water which is continuously converting into steam because of the geothermal energy. When the pressure becomes so high, it comes out as an explosion causing a volcanic eruption.
- A pyroclastic flow is the flow of molten semi-liquid lava away from the volcanic mountain, downhill.
Types of Volcanic mountains
On the basis of activity:
- Active Volcano: An active volcano erupt continuously in the present time. Example: Barren Island volcano at Andaman Nicobar Islands in India is the only active volcano of India. There are around 700 active volcanoes in the world, many under the sea.
- Dormant or sleeping volcanoes: These are the most dangerous volcanoes in the world. Sleeping volcanoes do not have any fixed time of the eruption , they can erupt any time. Example- Mt. Vesuvius in Italy, Mt. Krakatau in Indonesia and Mt. Kilimanjaro ( Tanzania).
- Extinct Volcano: An extinct volcano is the one which has not erupted for the last 10,000 years and is a dead volcano according to scientists. An extinct volcano has no lava supply in its magma chamber. Example- Mt. Thielson in Oregon USA is a dead volcano because it had last erupted 2,50,000 years ago.
On the basis of structure:
- Shield Volcano: Shield volcanoes are not so steep therefore lava flows to a great distance. Such volcanoes are wider and resemble warrior shields and hence its name. Shield volcanos are the largest of all types of volcanos.
- Cinder Volcanos: Cinder volcanoes are formed when upcoming lava of shield mountains moves in the form of shield mountains and comes out explosively. Cinder volcanoes have a steep slope and also a crater on the top.
- Composite volcanoes: Composite volcanoes do not have one but many vents. The lava flows with a mixture of volcanic rocks called cinders. The material accumulates in the form of layers over layers.
- Caldera: Caldera is created as a large depression due to a sudden explosion in the volcano, which collapses it.
Solved Question for you
Question: Explain how a volcano can give rise to Tsunami?
Answer: Tsunami generally occurs when an oceanic volcano erupts replacing a huge amount of water. As per an estimation, there are around 700 volcanoes under the sea. Most of these volcanoes are present in Pacific ocean belt of fire.