Rock formation processes - SS1 Agriculture Lesson Note

Rocks form through various geological processes that involve the transformation of existing materials into solid rock. The three main rock formation processes are:

 

Igneous Rock Formation:

Igneous rocks are formed from the solidification of molten material, either magma (beneath the Earth's surface) or lava (on the Earth's surface).

Magma, generated within the Earth's mantle, rises towards the surface. As it cools and solidifies, it forms igneous rocks.

The rate of cooling determines the size of crystals within the rock. Slow cooling leads to larger crystals, while rapid cooling results in smaller or no visible crystals.

Locations with volcanic activity often have extrusive igneous rocks, while intrusive igneous rocks are found beneath the Earth's surface.

 

Sedimentary Rock Formation:

Sedimentary rocks are created through the accumulation and compaction of sediments over time.

Weathering and erosion break down pre-existing rocks into sediments such as sand, silt, and clay. These sediments are transported by wind, water, or ice.

As sediments settle, they are compacted and cemented together, forming sedimentary rocks.

Fossils are often preserved in sedimentary rocks, providing valuable insights into Earth's history and past environments.

 

Metamorphic Rock Formation:

Metamorphic rocks form from the alteration of existing rocks (igneous, sedimentary, or other metamorphic rocks) under high temperature and pressure conditions.

Heat and pressure cause minerals within the rock to recrystallize and change their chemical composition.

The original rock, called the parent rock, undergoes metamorphism to become a new rock with different physical and chemical properties.

The degree of metamorphism can vary from low (e.g., shale to slate) to high (e.g., granite to gneiss).