rock cycle and types of rock

Igneous rocks

Igneous rocks comes from the cooling of magma that results in any crystalline or glass rock

Extrusive igneous formed by cooling on the surface of the earth

Intrusive igneous formed by cooling of magma within the earths crust.

Types of magma

Basaltic: high in iron, magnesium, calcium. Low in sodium and potassium

Andesitic: intermediate in all elements listed above

Rhyolitic: low in iron, magnesium and calcium. High in sodium and potassium.

Textures of igneous

Common fold with crystal nucleation and growth

Can have a glassy look ( obsidian)

Sedimentary rocks

70% of earths rocks are sedimentary in origin

Once deposited sediments undergo diagenesis

Diagenesis involves physical, chemical and/or biological processes which bring about compaction, cementation, recrystallisation and/or other modifications to an original sediment

Categories of sedimentary rocks

Siliciclastic - consists of fragments or clasts of pre existing rock transported by physical processes

Organic sediments

Chemical sediments

Volcaniclastic - lava and rock fragments derived from volcanic activity.

Metamorphic rocks

Process of change where original rock recrystallises in new conditions to produce a new type of rock that contains new minerals.

Types of metamorphic change

Phase change - replacement of original minerals with new metamorphic minerals as a result of a chemical reaction

Textural changes - recrystallisation to produce new minerals

ALL METAMORPHISM OCCURS IN A SOLID STATE OTHERWISE IT WOULD BECOME IGNEOUS ROCK AGAIN