Disaster and Earth Science

Lecture 1; The Rock


What is Rocks?

A rock is a naturally occurring solid mixture of one or more minerals or organic matter

Rocks are classified by how they are formed, their composition, and their texture

Rocks change over time through the rock cycle

Igneous rock begins as magma.

Magma can form:

  • When the rocks is heated
  • When pressure is released
  • When rocks change the composition
  • Magma freezes between 700 °C and 1,250 °C
  • Magma is a mixture of many minerals

Types of Igneous Rocks

  • Felsic: light-colored rocks that are rich in elements such as aluminum, potassium, silicon, and sodium
  • Mafic: dark colored rocks that are rich in calcium, iron, and magnesium, poor in silicon
  • Coarse-grained:  takes longer to cool, giving mineral crystals more time to grow
  • Fine-grained: cools quickly with little to no crystals 

>>Full Lecture1: The Rocks