Lesson 2.2: Rocks and the Rock Cycle

rock

naturally-occurring, coherent aggregate of minerals or solid materials such as natural glass or organic matter

lithosphere

rigid, rocky, outermost part of Earth, composed of the crust and uppermost part of the upper mantle.

rock cycle

It is a model that describes all the processes by which rocks are formed, modified, transported, decomposed, melted, and reformed.

magma

molten rock beneath the surface

lithification

transforms sediments into sedimentary rocks

Igneous Rocks

formed from the cooling and solidification of magma or lava

below the surface (from slowly cooling magma), on the surface (from rapidly cooling lava), on the surface (from the consolidation of particle erupted by explosive volcanic activity)

What are the three ways in which igneous rocks can form?

Below the surface (from slowly cooling magma)

This results in the formation of crystals that are visible to the naked eye without the aid of a magnifying lens.

Intrusive or Plutonic

These types of igneous rocks cool underneath the surface as plutons.

On the surface (from rapidly cooling lava)

This results in the formation of very small crystals that may not be visible without the use of a magnifying lens.

Extrusive or Volcanic

These types of igneous rocks are usually extruded during volcanic eruptions.

On the surface (from the consolidation of particle erupted by explosive volcanic activity)

When volcanoes erupt violently, the lava exiting the volcanoes are ripped apart into smaller pieces by rapidly expanding gases in the lava, just like the bubbles in a bottle of soft drinks shaken vigorously.