Unit 3 Lesson 4 How Can Rocks Be Classified? Copyright © Houghton Mifflin Harcourt Publishing Company 1

Unit 3 Lesson 4 How Can Rocks Be Classified? Florida Benchmark SC.4.E.6.1 Identify the three categories of rocks: igneous (formed from molten rock); sedimentary (pieces of other rocks and fossilized organisms); and metamorphic (formed from heat and pressure). Copyright © Houghton Mifflin Harcourt Publishing Company 2

Unit 3 Lesson 4 How Can Rocks Be Classified? Igneous Rock Rock is a natural solid that is made of one or more minerals. Rocks are classified by how they form. There are three main groups of rock: igneous rock, sedimentary rock, and metamorphic rock. Copyright © Houghton Mifflin Harcourt Publishing Company 3

Unit 3 Lesson 4 How Can Rocks Be Classified? Igneous Rock Igneous rock forms when melted rock, or magma, cools and hardens. Magma can cool at different rates. The way the magma cools determines what kind of igneous rock forms. Copyright © Houghton Mifflin Harcourt Publishing Company 4

Unit 3 Lesson 4 How Can Rocks Be Classified? Igneous Rock An igneous rock that cools slowly deep underground has large crystals. An igneous rock that cools faster has smaller crystals. An igneous rock that cools very quickly does not have crystals. Copyright © Houghton Mifflin Harcourt Publishing Company 5

Unit 3 Lesson 4 How Can Rocks Be Classified? Sedimentary Rock Rocks that form from sediments that are squeezed and cemented together are called sedimentary rock. Sometimes traces of dead plants and animals called fossils are found in sedimentary rock. Copyright © Houghton Mifflin Harcourt Publishing Company 6

Sedimentary Rock Describe how the sediment changes into rock. Unit 3 Lesson 4 How Can Rocks Be Classified? Sedimentary Rock Describe how the sediment changes into rock. Copyright © Houghton Mifflin Harcourt Publishing Company 7

Unit 3 Lesson 4 How Can Rocks Be Classified? Metamorphic Rock A rock that is changed by heat and pressure deep inside Earth is called a metamorphic rock. Heat and pressure can change the way a rock looks and may even cause a rock’s minerals to change into other minerals. Copyright © Houghton Mifflin Harcourt Publishing Company 8

Useful Rocks Metals are used to make cars, silverware, and jewelry. Unit 3 Lesson 4 How Can Rocks Be Classified? Useful Rocks Metals are used to make cars, silverware, and jewelry. Obsidian was used by people long ago to make tools. Today it is used to make surgery tools. Copyright © Houghton Mifflin Harcourt Publishing Company 9

Unit 3 Lesson 4 How Can Rocks Be Classified? Useful Rocks Many old buildings and monuments are made of limestone. Today it is used in many homes and office buildings. Many building materials, such as cement, concrete, and drywall, are made from rocks. Copyright © Houghton Mifflin Harcourt Publishing Company 10

Unit 3 Lesson 4 How Can Rocks Be Classified? Useful Rocks Toothpaste is made from several minerals extracted from rocks. Many statues and monuments are made of marble. Copyright © Houghton Mifflin Harcourt Publishing Company 11

Unit 3 Lesson 4 How Can Rocks Be Classified? The Rock Cycle The continuous process in which one type of rock changes into another type is known as the rock cycle. Any kind of rock can become any other kind of rock. Copyright © Houghton Mifflin Harcourt Publishing Company 12