Several integrated processes such as gradual increase in temperature with the depth, due to the heat generated by degeneration of radioactive elements inside the earth.
Origin of magma due to the lowering of the melting point caused by reduction in pressure of overlying rocks due to fractures caused by splitting of plates.
Classification of volcanoes –
On the basis of mode of eruption:
Central eruption or explosive type.
Example: Hawaiian type, Strombolian type, Pelean type, Visuvious type, volcanic type etc.
Fissure eruption or quiet eruption.
Successive flow of lava results in the growth of lava plateau. Example: Deccan plateau etc.
On the basis of periodicity of eruption:
Active volcano.
Erupts periodically.
Example: Etna, Stromboli, Mayon etc.
Dormant volcano.
Volcano which becomes quiet after its eruption for some time.
Example: Fujiyama, Krakatoa, Barren Island etc.
Extinct volcano.
No indication of future eruption.
Various volcanic belts –
Circum pacific belt.
Fire girdle of the pacific or the fire ring of the pacific.
It extends across the Kamchatka peninsula, Kurile Islands, the islands of Japan, Philippines, New Guinea, New Zealand and the soloman islands.
Mid continental belt.
Volcanic zones of convergent continental plate margins.
Includes volcanoes of alpine mountain chain, the Mediterranean sea and the fault zone of eastern Africa of Stromboli, Vesuvius, Etna, Kilimanjaro.
Mid Atlantic belt.
Fissure eruption type.
Example: Iceland, Canary Islands, Cape Verde, Azores etc.
Highest volcanic peaks are Cotopaxi (South America), Fujiyama (Japan) and Valley of Ten Thousand Smokes (Alaska).
Weathering –
Physical weathering.
Factors are temperature change, Crystallization of water into ice, the pressure release mechanism etc.
Chemical weathering.
Factors are solution, oxidation, carbonation, hydration, hydrolysis and chelation.
Biological weathering.
Three types Faunal, Floral and Anthropogenic.
Rocks (can be defined as an aggregate of minerals).Depending upon the process of their formation –
Igneous rocks / Primary rocks.
Formed due to the cooling, solidification and crystallization of hot and molten magma.
Believed that they are formed during each period of geological history of the earth.
Are hard, granular and crystalline rocks.
Less affected by chemical weathering.
It does not have any fossil or does not form any strata or layers of lava.
Classification of igneous rocks
On the basis of mode of occurrence –
Intrusive rocks.
Formed due to solidification of rising magma below the surface of the earth.
Example: Granite, Lapolith, Batholiths, Sills etc.
Extrusive rocks.
Formed due to cooling and solidification of hot and molten magma at the earth surface.
Example: Basalt, Gabbro etc.
On the basis of silica content –
Acidic.
Has more silica content. Example: Granite.
Basic.
Has less amount of silica content. Example: Gabbro.
Sedimentary rocks.
Formed due to the aggregation and compaction of sediments derived from the older rocks, plants, animals and contains fossils of plants.
Can be classified on the basis of the nature of sediments –
Mechanically formed rocks.
Chemically formed rocks.
And organically formed rocks.
Metamorphic rocks.
Changed form of igneous and sedimentary rocks.
Are the rocks which change either in form or composition without disintegration.
Are metamorphosed.
Agents of metamorphism are heat, compression and solution.