Types of Rocks

Types of Rocks

• Rocks are defined as naturally occurring aggregates of geological material, called minerals.
• The three major types of rocks are igneous rocks, sedimentary rocks, and metamorphic rocks.

Igneous Rocks

• Igneous rocks are formed from the cooling and solidification of molten rock (magma).
• Magma can cool and solidify beneath the Earth's crust or on the surface, resulting in two types of igneous rocks:
  • Intrusive igneous rocks: solidify within the Earth's crust, characterized by large, visible crystal formations.
  • Extrusive igneous rocks: formed by the cooling and solidification of lava on the Earth's surface, characterized by rapid cooling and small, invisible crystal structures.

Examples of Igneous Rocks

• Intrusive igneous rocks: granite and diorite.
• Extrusive igneous rocks: basalt.

Sedimentary Rocks

• Sedimentary rocks are defined as lithified sediments.
• Sediments can come from:
  • Weathering of rocks due to forces like wind and water.
  • Dead organic matter.
  • Precipitated salts.
• Accumulated sediments can become lithified (turned into rock) due to compaction, cementing, or other processes.

Types of Sedimentary Rocks

• Clastic sedimentary rocks: formed by the lithification of sediments called clasts, produced by the weathering of other rocks.
• Organic sedimentary rocks: formed by the lithification of sediments from organic materials, such as bones, shells, and teeth.
• Chemical sedimentary rocks: formed when water evaporates and produces sediments of dissolved matter.

Examples of Sedimentary Rocks

• Clastic sedimentary rocks: siltstone and sandstone.
• Organic sedimentary rocks: limestone.
• Chemical sedimentary rocks: sea salt.

Metamorphic Rocks

• Metamorphic rocks are formed through the metamorphosis of sedimentary or igneous rocks.
• Metamorphosis is the change in rock type due to environmental factors like heat, pressure, or chemical environments.

Types of Metamorphic Rocks

• Foliated metamorphic rocks: characterized by the presence of parallel bands of minerals running through the rock.
• Unfoliated metamorphic rocks: formed when pressure is milder across the rock during the process of metamorphosis.

Types of Metamorphism

• Contact metamorphism: occurs when magma rises to the upper crust of the Earth, generating high heat and low pressure conditions.
• Regional metamorphism: occurs at convergent tectonic margins, where two continental plates collide, generating high heat and pressure conditions.
• Dynamic metamorphism: occurs as a result of mechanical deformation, often seen along fault lines.

Examples of Metamorphic Rocks

• Unfoliated metamorphic rocks: marble.
• Foliated metamorphic rocks: slate and phyllite.

The Rock Cycle

• The rock cycle describes how geological material, such as rocks and minerals, are cycled over time.
• It considers the relation between igneous, sedimentary, and metamorphic rocks and how transformations occur between each type.
• The rock cycle is a continuous process where rocks can change from one type to another due to various environmental factors.