Geothermal Energy: The thermal energy generated and stored in the Earth; its main sources are magmatic activities and radioactive decay.

(v) Volcanic Winter: A volcanic winter is the reduction in temperature of a global zone caused by the volcanic ash and droplets of sulfuric acid which obscure the sun and sunshine and cool the Earth's lower atmosphere ,forexample, troposphereRocks Formed: When the magma cools down, it solidifies and forms the igneous rocks. The type of rocks formed depends upon the chemical composition of the magma and how rapidly the magma cools. This magma when reaches on the surface of earth becomes lava, it cools down quite rapidly resulting in the rocks having fine grains or very small crystals, the rocks are known as Volcanic Rocks, such as Basalt. Some of this magma cools down extremely rapidly and forms the Volcanic Glass (volcanic rocks without the crystals, look like a glass or have glassy formation) such as Obsidian.

Magma that remains trapped inside the earth, cools down slower than the magma ejected to the surface i.e. lava and produces the rocks with medium to coarse sized crystals. And the Magma that remains trapped in the large quantities very deep in the earth cools down most slowly resulting in the rocks having quite large crystals such as Granite and GabbroExisting rocks that come into contact with the very hot boiling magma get melted and absorbed into the magma. Other rocks a little far from the magma get altered by the process of Contact Metamorphism or Metasomatism, when they are affected by the big heat and circulating hydrothermal fluids.

Volcanoes: A volcano is an opening in the surface which allows hot magma, volcanic ash and gases to escape from the magma chamber deep below the earth surface.Volcanoes are generally formed where Tectonic Plates are converging or diverging. A Mid Ocean Ridge (a general term for underwater usually oceanic mountains), forexample, Mid Atlantic Ridge , has the volcanoes caused by Divergent Tectonic Plates. Pacific Ring of Fire (a very big horse-shoe shaped ring [40, 000 km long] containing about 450 volcanoes along the continental shore of Pacific Ocean) has the volcanoes caused by Convergent Tectonic Plates colliding together.

Hotspots: These are the volcanic regions thought to be fed by the underlying mantle which is unusually hot as compared to the normal mantle.