Chapter 8 Lesson 2 "Igneous Rocks"

Materials:

• Worksheet, "Igneous Rocks"
• Samples of different material, cotton, velvet, wool, and polyester

Objective:

• Students will explain how igneous rocks form.
• Students will compare intrusive and extrusive igneous rocks.
• Students will identify samples of igneous rocks.

Anticipatory Set:* Students will be shown four different types of cloth, cotton, velvet, wool, and polyester. Samples will be passed around and the student will expain the difference in the material. When you discuss how they feel show the student the four samples under a microscope and explain that their texture is determined by how they are structured on a microscopic level. The same is true for rock.

Teacher Input:* Students will make a table like the one below. In the table they will list Characteristics of Intrusive Igneous Rocks and Extrusive Igneous Rocks.

Start by showing the student a picture of a volcano and have them explain how a volcano works. Show the layers of the earth and explain that the magma his heated which makes it less dense than the crust this causes it to want to rise above the crust. Lucky for us that the crust forms a seal that doesn't let out a lot of Magma. There are two ways that the magma can cool. Underground as it moves toward the surface it melts rocks. Eventually it cools then forms new rock. Next, students will look at a cut away picture of a volcano. Ask the student which type of rock is an intrusive rock. Because it cools slowly the crystals that form are very large. Igneous Rock texture 1, 2, 3. The crystals are often so large that they can be identified.

Extrusive igneous rock starts out as this red substance known as _________. As the lava cools it turns into rock. It cools so quickly that only small grain crystals form. Andesite, pumice, and rhyolite. Don't get confused in the rough feel of some Extusive Igneous rock. The rough feel is from air pockets in the rock. Not large grains. When there is no gases then the rock forms very smoothly. Obsidian.Because of the very small grains it can be shaped into very sharp edges.

Check to make sure students were able to fill in their tables.

Guided Practice:* Students will answer the questions on Page 184 with their teacher.

Independent Practice:* Students will complete the worksheet, "Igneous rock."

Check for Understanding:* Students will complete the quiz, Lesson 2, Igneous Rocks.

Duration:

30 minutes + 10-15 for Independent Practice (Could be longer if taken for homework).

Alaska Content Standards Addressed in this lesson:

• SCI A-1 Students will understand models describing the nature of molecules, atoms, and sub-atomic particles and the relation of the models to the structure and behavior of matter (Structure of Matter);