1. Once a rock forms as part of a mountain, it does not change. Do you agree or disagree? 1. Once a rock forms as part of a mountain, it does not change. 2. Some rocks, when exposed on Earth’s surface, undergo weathering and erosion. Lesson 1 - Now

Lesson 2 Reading Guide - KC Igneous Rocks How do igneous rocks form? What are the common types of igneous rocks? Lesson 2 Reading Guide - KC

Lesson 2 Reading Guide - Vocab Igneous Rocks extrusive rock volcanic glass intrusive rock Lesson 2 Reading Guide - Vocab

Igneous Rock Formation When volcanic material erupts and cools and crystallizes on Earth’s surface, it forms a type of igneous rock called extrusive rock. Volcanic glass is rock that forms when lava cools too quickly to form crystals. Among the most noticeable features of some extrusive igneous rocks are holes that are left after gas escapes. Lesson 2-1

Igneous Rock Formation (cont.) Igneous rocks that form as magma cools underground are called intrusive rocks. intrusive from Latin intrudere, means “to push in” Lesson 2-1

Intrusive and Extrusive Rocks Lesson 2-1

Igneous Rock Formation (cont.) How do igneous rocks form? Lesson 2-2

Geologists determine whether an igneous rock is extrusive or intrusive by studying the rock’s texture. Lesson 2-2

Igneous Rock Identification If the crystals are small, the rock is extrusive. If all the crystals are large enough to see and have an interlocking texture, the rock is intrusive. Lesson 2-2

Igneous Rock Identification (cont.) Igneous rocks are also classified, in part, by magma composition, such as silica content. Magma composition, the location where the lava or magma cools and crystallizes, and the cooling rate determine the type of igneous rock that forms. Lesson 2-2

Igneous Rock Identification (cont.) How are extrusive and intrusive rocks different? Lesson 2-2

When lava cools fast, volcanic glass forms. An extrusive igneous rock cools and crystallizes from volcanic material erupted on Earth’s surface. When lava cools fast, volcanic glass forms. An intrusive igneous rock forms as magma cools and crystallizes deep inside Earth. Lesson 2 - VS

What erupts onto Earth’s surface during a volcanic eruption? A. sediment B. volcanic glass C. pumice D. magma Lesson 2 – LR1

Which of these forms when lava cools too quickly to form crystals? A. extrusive rock B. intrusive rock C. volcanic glass D. magma Lesson 2 – LR2

What kind of rock forms when magma cools underground? A. intrusive B. extrusive C. crystallized D. mineral Lesson 2 – LR3

3. Large crystals form when lava cools quickly on Earth’s surface. Do you agree or disagree? 3. Large crystals form when lava cools quickly on Earth’s surface. 4. Igneous rocks form when cooling magma crystallizes. Lesson 2 - Now