100+ Volcanoes, Mountains, Earthquakes, Plateau Gk Quiz Questions - 2

Question: 6

What is a shield volcanoe?

When a large amount of free flowing lave spills from a central vent, the volcanoe takes the shape of a broad, slightly dome structure. This is called a shield volcanoe.

They are primarily of basaltic lava flows.

Question: 7

How are volcanoes formed?

Most magma forms 80 to 160 kms beneath the surface of the earth.

As the magma rises, it melts gaps in the surrounding rock and forms a large chamber.

This magma chamber is the reservoir from which volcanic materials erupt.

The gas filled magma in the reservoir is under pressure from the weight of the solid rock around it.

This pressure causes the magma to blast or melt a channel in a fractured or weakened part of the rock.

The magma moves up through the conduit (channel) to the surface.

When the magma nears the surface, the gas in the magma is released.

This gas and magma blast out an opening called the central vent. Most magma and other volcanic materials then erupt through this vent.

The materials gradually pile up around the vent, forming a volcanic mountain or Volcanoe.

Question: 8

Give examples of composite cone volcanoes of the world?

A narrow zone named the Ring of Fire surrounds the Pacific Ocean. Fujiyama in Japan. Mt Mayaon in the phillipines and the picturesquare volcanoes of cascade Range in the Northwestern United States including St. Helens in USA are also examples of composite cone volcanoes.

Question: 9

Why the Himalayas are called the young fold mountains?

The Himalayas are formed by the folding of the sedimentary rocks during lateral drift. Hence they are called as the young fold mountains.

Question: 10

Give an account of the Andaman Nicobar Islands?

The Andaman Nicobar Islands are found in the east of Chennai in the Bay of Bengal with a north south distribution.

In the north of these islands are the Andamans and in the south of these are the Nicobar group.

In the Andaman group of islands, there are 300 islands which are both small and large.

Of these, only five islands are inhabited by the humans.

In most of the Nicobar islands, there are tribes.