Lecture Notes: The Rock Cycle

Overview of Rocks

• Three main types of rocks:
  • Igneous
  • Sedimentary
  • Metamorphic
• Topics covered:
  • Origins
  • Mineralogy
  • Properties

Introduction to the Rock Cycle

• Definition:
  • A process that describes how rocks transform from one type to another.
• Key processes:
  • Formation and destruction of rocks throughout geologic history.

Historical Context of Rock Formation

• Igneous Rocks:
  • Initially, all surface rocks were igneous.
  • Formed from the cooling of liquid magma.
• Sedimentary Rocks:
  • Over time, rain and wind break down igneous rocks, transporting sediments to oceans.
  • Sediments are buried and lithified into sedimentary rocks.
• Metamorphic Rocks:
  • In regions where tectonic plates collide, original igneous rocks metamorphose due to heat and pressure, forming mountains.
  • These rocks can also erode back into sediments.

Rock Transformation Processes

• Cycle:
  1. Igneous rock can melt into magma.
  2. It can also undergo weathering and erosion to form sediments.
  3. Sediments compact and cement to form sedimentary rock.
  4. Metamorphic rock can form from igneous or sedimentary rocks through heat and pressure.
  5. Both sedimentary and metamorphic rocks can weather and erode into sediments again.
  6. Metamorphic rock can also melt to produce magma.

Unique Geological Examples

• Jack Hills Conglomerate (Australia):
  • Contains detrital zircon, a durable mineral over 4.4 billion years old.

The Role of Weathering and Erosion

• Introduced but not detailed yet; will discuss next.
• Weathering and erosion are critical for transforming rocks into sediments.