Igneous Rock 3.2

Igneous Rock 3.2 Igneous rock forms when magma cools and hardens NBpg. 34 Slide 1 of 4 Igneous Rock 3.2 What are the types of Igneous rocks and how are they different? Igneous rock forms when magma cools and hardens Three factors that affect when rock melts are temperature, pressure, and fluid in the rock Rock melts at its melting point Pressure can raise the melting point Added liquid lowers the melting point Rocks Types of rocks

The Rock Cycle Partial Melting NBpg. 34 Slide 2 of 4 The Rock Cycle Partial Melting Different minerals have different melting points Minerals with lower melting points melt first As minerals melt the chemical composition of the magma changes This process is called partial melting Fractional Crystallization Is the process in reverse

The Rock Cycle 2 classes of igneous rock: NBpg. 34 Slide 3 of 4 The Rock Cycle 2 classes of igneous rock: when magma intrudes into rock masses beneath the surface slower cooling gives time to form well-developed crystals have a coarse-grained texture Example: Granite which makes up most of the continental crust Textures of Igneous Rock Intrusive Rocks

The Rock Cycle Extrusive NBpg. 34 Slide 4 of 4 The Rock Cycle Extrusive Formed by lava which is magma that has exited the earth Most extrusive igneous rocks have small mineral grains that can not be seen by the unaided eye caused by the rapid cooling not giving enough time for large crystals to form. These are said to have a fine-grained texture Example Obsidian

Granite and Rhyolite