Title: Chapter 5.1, What are Igneous Rocks? Table of Contents Title: Chapter 5.1, What are Igneous Rocks? Page #: 31 Date: 11/19/2012

Objective Students will be able to compare and contrast magma and lava. Students will be able to describe the formation of igneous rocks. Students will be able to identify igneous rocks.

Words of the Day Magma: Molten rock below Earth’s surface. Lava: Molten rock that flows onto Earth’s surface.

Igneous Rocks Igneous Rocks: Rocks that form when molten material (Magma or Lava) cools and crystallizes. Formation of Igneous Rocks: Happens when magma cools beneath Earth’s surface. Happens when lava cools on Earth’s surface.

Igneous Rocks Composition of Magma: 3 ingredients Molten rock Dissolved gasses Mineral crystals

Igneous Rocks Elements in Magma: Oxygen (O) Silicon (Si) - Most abundant Aluminum (Al) Iron (Fe) Magnesium (Mg0 Calcium (Ca) Potassium (K) Sodium (Na)

Igneous Rocks Classification of Magma (based on Silica content): Basaltic 42% - 52% Silica Andestic 52% - 66% Silica Rhyolitic more than 66% Silica The more Silica in Magma, the lighter is its color.

Igneous Rocks Magma and lava are different: Magma is underground Lava is on Earth’s surface Lava does not contain dissolved gasses because they escape into the atmosphere.

Igneous Rocks 4 Factors of Magma Formation: Temperature Pressure Water Content Mineral Content Geothermal Gradient - Temperature and pressure increase as you get deeper into Earth. Increase in pressure raises the melting temperature of rocks.

Igneous Rocks Mineral Content: Mineral content of magma determines its characteristics. Different minerals have different melting points. Basalt has a higher melting temperature than granite because it contains different minerals.

Igneous Rocks Partial Melting: Because different minerals have different melting temperatures it is possible for magma to contain some solids. Result: Magma at different temperatures will have different compositions.