Earth Movements

Interior Structure of the Earth

The Crust

The Mantle

The Core

Crustal Plates

Theory of Plate Tectonics


  1. Granite - volcanic rock with large crystals formed by slow cooling of magma beneath the Earth's surface
  2. Basalt - volcanic rock with small crystals formed by rapid cooling of lava on the Earth's surface
  3. Pumicestone - volcanic rock filled with air bubbles formed by the ejection and rapid cooling of lava in the air
  1. A crater lake may form when rain fills the cooled volcanic crater.
  2. If the volcano sides erode over time leaving the solid vent, mountains such as the Glasshouse Mountains are formed.
  3. If a volcano has not erupted in a long time but may erupt again, it is said to be dormant (sleeping).
  4. If a volcano has not erupted in a very long time and probably will not erupt again, it is called extinct.
  1. Shield Cone - Wide at the base with gentle slopes, formed by gentle volcanoes
  2. Cinder Cone - Narrow at the base, steep slopes built up by angular interlocking cinders (ash), formed by explosive volcanoes
  3. Composite Cone - Intermediate between the shield and cinder cones, built up from alternating layers of lava and cinder
  4. Dome Mountain - Magma pushes up through sedimentary rock


  1. P Waves - Primary or push waves that travel deep beneath the Earth's surface at about 5.5 to 13.5 km/s
  2. S Waves - Secondary or shake waves that travel deep beneath the Earth's surface at about 3.7 to 7 km/s
  3. L Waves - Longitudinal waves that travel along the Earth's surface at about 3.2 km/s, causing greatest damage to buildings, landslides and tsunamis (tidal waves)