The Story of: Igneous Rocks Section 4-2 Explain how the cooling rate of magma affects the rock texture Distinguish between Intrusive & Extrusive Igneous rocks

Science Starter: 1. Using your notes & section 4.2 in the book, create a T-chart explaining the differences between Intrusive & Extrusive Igneous rocks. Intrusive Extrusive

Igneous Rock Igneous = Latin word for “fire” Rocks formed from the cooling of magma (or lava).

Magma Formation 3 ways magma can form: (p. 98) Rock is HEATed When PRESSURE is released When rock changes COMPOSITION

Classification of Igneous Rocks: Composition: what minerals are in the rock Texture: size of the rocks’ mineral grains(crystals) Eg. Large grains or small grains

Composition of Igneous Rocks: Composition determines rock color Dark Colored = Mafic Made of elements: Calcium, Iron & Magnesium More Dense Basalt

Composition of Igneous Rocks: Light Colored = Felsic Made of elements: aluminum, potassium, silicon Less Dense Rhyolite

Texture of Igneous Rocks: How quickly magma cools determines rock texture Cools slowly= more time for crystals to grow More time for crystals to grow= larger crystals Intrusive Igneous Rock Granite (coarse-grained)

Texture of Igneous Rocks: Cools quickly= little/no time for crystals to grow no crystals or small crystals Extrusive Igneous Rock Obsidian (volcanic glass)

Igneous rocks form from molten rock. 4.2 Igneous rocks form from molten rock. As molten rock cools, minerals crystallize and form Ig. rocks. intrusive igneous rock Extrusive igneous rocks cool quickly at Earth's surface. extrusive igneous rock Intrusive igneous rocks cool slowly within Earth.

Igneous rocks form from molten rock. 4.2 Igneous rocks form from molten rock. As molten rock cools, minerals crystallize and form Ig. rocks. intrusive igneous rock Extrusive igneous rocks cool quickly at Earth's surface. extrusive igneous rock Intrusive igneous rocks cool slowly within Earth.

Igneous Rock-Intrusive vs. Extrusive Extrusive Igneous Rock: Cools quickly at Earth’s surface Intrusive Igneous Rock: Cools slowly within Earth What Texture will Extrusive rocks have? What Texture will Intrusive rocks have?

Magma Formation, cont. Temperature An increase in temperature from the earth’s interior can cause minerals in rock to melt. Different minerals have different melting points.

Magma formation cont. Pressure: Earth’s interior=high pressure=rocks stay in their solid form. As rocks move towards earth’s surface there is less pressure and it sometimes causes them to melt.

Magma formation cont. Composition- Sometimes fluids enter a rock and change its melting point, and ultimately the composition of the rock itself.

Igneous Rock Vocabulary: Composition: Texture:

Igneous Rock Vocabulary Composition: Texture: