Types of Rocks and Their Formation

Types of Rocks

  • Igneous
  • Sedimentary
  • Metamorphic

Igneous Rock

  • Formed from magma that cools and solidifies.
  • Types:
    1. Plutonic (intrusive): Cools slowly inside Earth (e.g. granite).
    2. Volcanic (extrusive): Cools quickly on surface (e.g. basalt).
  • Characteristics:
    • Coarse-grained, resistant to erosion.
    • Contains minerals like feldspar, quartz, and mica.
    • Can vary in color (white, grey, pink, black).
    • Granite example: forms from magma during subduction.
    • Basalt: fine to medium-grained, world's most common rock type.

Sedimentary Rock

  • Formed from sedimentation and lithification.
  • Two types:
    1. Inorganic (e.g. sandstone).
    2. Organic (e.g. limestone).
  • Characteristics:
    • Limestone formed from the remains of marine life under high pressure.
    • Can contain fossils, varies in color (grey, white, black).
    • Sandstone: coarse-grained, formed in desert climates.

Metamorphic Rock

  • Formed from heat and pressure affecting igneous or sedimentary rocks.
  • Types:
    1. Thermal/contact metamorphism (heat from magma).
    2. Regional metamorphism (heat and pressure over large areas).
  • Examples:
    • Limestone to marble (e.g. Connemara).
    • Sandstone to quartzite (e.g. Croagh Patrick).

Rock Cycle

  • Continuous process of formation, destruction, and reformation of rocks.
  • Involves melting, denudation, compaction, and sedimentation.

Case Study: Geothermal Energy

  • Renewable energy sourced from volcanic activity near the surface, e.g. Iceland.