Types of Rock Formation to Know for Earth Systems Science

Rocks form through various processes that shape our planet. Understanding igneous, sedimentary, and metamorphic rock formations reveals how Earth's systems interact, reflecting geological history and environmental changes over time. Each rock type tells a unique story about our planet's evolution.

1. Igneous rock formation

   • Formed from the cooling and solidification of molten rock (magma or lava).
   • Can be classified into two main types: intrusive (plutonic) and extrusive (volcanic).
   • Common examples include granite (intrusive) and basalt (extrusive).

2. Sedimentary rock formation

   • Created through the accumulation and compaction of mineral and organic particles.
   • Often formed in layers, indicating the historical environment of deposition.
   • Includes three main types: clastic, chemical, and organic sedimentary rocks.

3. Metamorphic rock formation

   • Formed from existing rocks (igneous, sedimentary, or other metamorphic rocks) undergoing changes due to heat, pressure, or chemically active fluids.
   • Can exhibit foliation (layering) or non-foliated textures based on the conditions of formation.
   • Examples include schist (foliated) and marble (non-foliated).

4. Volcanic rock formation

   • A subset of igneous rocks formed from lava that cools quickly on the Earth's surface.
   • Typically characterized by a fine-grained texture due to rapid cooling.
   • Common examples include pumice and obsidian.

5. Plutonic rock formation

   • A type of igneous rock that forms from the slow cooling of magma beneath the Earth's surface.
   • Characterized by a coarse-grained texture, allowing for the growth of large crystals.
   • Common examples include granite and diorite.

6. Chemical sedimentary rock formation

   • Formed from the precipitation of minerals from solution, often in bodies of water.
   • Typically includes rocks like limestone and rock salt.
   • Reflects the chemical environment and conditions of the water body where they formed.

7. Clastic sedimentary rock formation

   • Composed of fragments (clasts) of pre-existing rocks that have been weathered and eroded.
   • Classified based on grain size, with examples including sandstone (medium grain) and shale (fine grain).
   • Often contains fossils, providing insights into past environments.

8. Contact metamorphism

   • Occurs when rocks are heated by nearby molten magma or lava, leading to localized changes.
   • Typically results in non-foliated metamorphic rocks due to the high temperature and low pressure.
   • Commonly found in areas surrounding igneous intrusions.

9. Regional metamorphism

   • Involves large-scale changes in rocks due to high pressure and temperature over extensive areas, often associated with tectonic forces.
   • Can produce foliated metamorphic rocks, such as schist and gneiss.
   • Typically occurs in mountain-building regions (orogenies).

10. Foliated metamorphic rock formation

    • Characterized by a layered or banded appearance due to the alignment of mineral grains under pressure.
    • Formed through regional metamorphism, where pressure causes minerals to realign.
    • Examples include slate, schist, and gneiss, each representing different grades of metamorphism.