PRINCIPLES OF EARTH SCIENCE

The three stages according from the oldest to the youngest formation are granite , basalt and lastly andesite formation . This will discuss about the formation , composition , type of intrusion and cooling history of each stages

The granite formation is the oldest stage since granite is formed usually beneath the crust about 1 .5 km up to 50 km depth . Primarily granite is composed of silicon and alumina about 72 .04 and 14 .42 respectively . The formation of granite occurs through extreme metasomatism . Through metasomatism , elements are brought out by fluids like potassium

and calcium to convert the metamorphic rock to granite According to Himanshu K . Sachan (1999 , granite in the northern Himalaya starts its cooling history at 705 ?C and continued up to 650 ?C in the range of 1 .2-2 .8 kbar . The next stage is the basalt formation

Basalt is composed of magnesium oxide , calcium oxide and low amount of silicon , sodium oxide and potassium oxide . The formation of basalt occurs when there is a volcanic eruption either under or above the Mostly the formation of basalt occurs underneath the sea . Through the introduction of water the magma hardens to form the basalt . Basalt forms between 50km up to 100 km depth within the mantle and 150 km up to 200 km for some high-alumina basalt . The next stage will be andesite

The youngest of the formation is the perpendicular andesite . After basalt , the most common volcanic rock would be he andesite . The main composition of andesite is silica...