Rock Cycle

Scientific Description of the Rock Cycle

1.      Igneous Rocks
Igneous rocks form through the cooling and solidification of magma or lava.

o    When magma cools gradually beneath Earth’s surface, intrusive (plutonic) igneous rocks such as granite are produced.

o    Conversely, rapid cooling of lava at the surface yields extrusive (volcanic) igneous rocks, typified by basalt. 

2.      Sedimentary Rock Formation
Exposure of pre-existing rocks to weathering and erosion generates detrital particles (sediments). These sediments undergo transport, deposition, compaction, and cementation (collectively known as lithification), forming sedimentary rocks like sandstone and limestone. 

3.      Metamorphism
Under conditions of elevated pressure and temperature, sedimentary or igneous rocks undergo mineralogical and textural reconfiguration without complete melting, giving rise to metamorphic rocks such as schist, marble, or gneiss. Foliated structures often emerge during regional metamorphism, while contact metamorphism occurs adjacent to igneous intrusions.

4.      Return to Magma
Any rock type—igneous, sedimentary, or metamorphic—that is subducted or subjected to intense heat may undergo partial or complete melting, reforming as magma and perpetuating the cycle.