Explain the term geothermal energy. How can it be exploited ? Though it is economical yet it is not harnessed in most of the countries. Why ?

Geothermal energy is heat energy trapped in hot regions called hot spots when molten rocks are pushed upwards. When underground, water comes in contact with hot spots steam is generated. Steam trapped in rocks is routed through a pipe to a turbine to generate electricity.

Very few commercially viable sites are available where such energy can be exploited.

Detailed Answer:

The heat from the interior of the earth can be utilized as a source of energy under certain favorable conditions that are created by natural processes. This is known as geothermal energy.

Molten rocks formed in the deeper hot regions of Earth's crust are pushed upward and trapped in certain regions due to geological changes. These spots are called hot spots. Underground water when comes in contact of hotspots, it gets converted into steam due to heat of molten rocks (magma) and remains trapped between the rocks, at high pressure. This steam can be used to run turbines connected to electric generators.