Contents. Ohio Revised Standards and Model Curriculum Correlation Chart... 5

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2 Contents Ohio Revised Standards and Model Curriculum Correlation Chart Chapter 1 Earth Science Lesson 1 Earth s Internal Structure Lesson 2 Learning from Seismic Waves Lesson 3 The Theory of Plate Tectonics Lesson 4 Plate Motion and Earth s Changing Surface Lesson 5 The Effects of Erosion and Deposition Lesson 6 Studying Earth s Surface from Above Lesson 7 Evidence of Earth s History Chapter 1 Review Chapter 2 Life Science Lesson 8 Sexual and Asexual Reproduction Lesson 9 Patterns of Inheritance Lesson 10 Adaptations, Survival, and Extinction Lesson 11 Fossils and Evolution Chapter 2 Review Chapter 3 Physical Science Lesson 12 Force, Motion, and Inertia Lesson 13 Friction and Gravity Lesson 14 Electricity and Magnetism Lesson 15 Potential Energy Chapter 3 Review Investigations Investigation 1 Modeling Plate Movement Investigation 2 Making and Testing an Electromagnet Glossary Comprehensive Review

3 Chapter 1 Lesson 1 Earth s Internal Structure Key Words crust continental crust oceanic crust mantle asthenosphere core lithosphere tectonic plate convection theory of plate tectonics model Getting the Idea Earth resembles a hard-boiled egg with a cracked shell. A hard-boiled egg has three main parts: the shell, the egg white, and the yolk. Earth also has three parts: the crust, the mantle, and the core. Like a cracked eggshell, Earth s crust is made up of smaller pieces, known as plates. The Formation of Earth Earth s internal structure is the result of how the planet formed, about 4.6 billion years ago. Early Earth was hot so hot that it was completely melted. Heavier elements, such as iron and nickel, sank to the center and formed Earth s core. Lighter elements remained near the surface. These lighter materials cooled to produce a solid outer layer of rock. The process in which heavier and lighter elements separated is called planetary differentiation. Other planets in our solar system were formed by the same process at around the same time. Earth s Crust Earth s outermost layer is the crust. The crust is Earth s thinnest layer, ranging from about 5 kilometers to about 100 kilometers thick. The crust makes up only about 1 percent of Earth s mass. Earth has two kinds of crust, continental crust and oceanic crust. Continental crust is the lighter, older, and thicker part of the crust that makes up the continents. Oceanic crust is the thinner, denser rock that makes up the ocean floor. In the 1970s and 1980s, scientists drilled a hole into Earth s crust in what was then the Soviet Union. They reached a depth of more than 12 kilometers before they had to stop. At that point, increasing heat made drilling impossible. 14

4 Earth s Mantle The mantle is the layer of Earth beneath the crust. The mantle is about 2900 kilometers thick and makes up nearly 67 percent of Earth s mass. Crust km thick Mantle Asthenosphere 2900 km Lithosphere Upper mantle Lower mantle Outer core Inner core 5100 km NOTE: To scale 6378 km NOTE: Not to scale There are two main layers in the mantle: the upper mantle and the lower mantle. The top of the upper mantle is solid, but great heat and pressure make the middle of the upper mantle soft. This region of hot, soft rock is called the asthenosphere. The rock in the asthenosphere flows slowly, like a very thick liquid. Below this region is a transition zone. Scientists believe the lower mantle is solid, although it is even hotter than other parts of the mantle. In the lower mantle, the pressure is so great that it keeps the rock from melting. Earth s Core Earth s innermost layer is the core. It is about 3500 kilometers thick and makes up about 33 percent of Earth s mass. The core is made up mainly of iron, with a small amount of nickel and other elements. It consists of two parts: the inner core and the outer core. The outer core is liquid. It consists of extremely hot, melted rock. Enormous pressures keep the inner core solid. At the center of the core, the temperature is greater than 6000 C, and the pressure is 4 million times greater than the air pressure at Earth s surface. Tectonic Plates The crust and the solid part of the upper mantle make up the lithosphere. The lithosphere is divided into giant, slow-moving chunks of rock called tectonic plates. You can think of the lithosphere as a jigsaw puzzle. Each tectonic plate is a piece of the puzzle. Tectonic plates float on the asthenosphere below. 15

5 Tectonic plates move because of convection currents in the asthenosphere. Convection is the transfer of heat by the movement of a fluid that is, a liquid or a gas. When a region of a fluid absorbs heat energy, that region expands and becomes lighter. The warm fluid floats upward as cooler, heavier fluid sinks beneath it. This process creates circular convection currents of warmer fluid rising and cooler fluid sinking. Because rock in the asthenosphere is so soft, it can transfer heat through convection, as a fluid does. Heat coming from the core causes rock in the lower part of the asthenosphere to expand and rise. As the rock gets closer to Earth s surface, it cools and sinks. Rising currents in the asthenosphere push the plates in the lithosphere apart. Sinking currents pull plates toward each other. The theory that describes these processes is called the theory of plate tectonics. You will learn more about this theory in Lesson 3. Atlantic Ocean South America Africa Plate Plate Plate Denser material sinks. Heated material expands and rises. 16 Chapter 1: Earth Science

6 Lesson 1: Earth s Internal Structure Focus on Inquiry A model is a representation of an object, system, or process. A model may be a diagram, a three-dimensional object, or a computer program. A model may also be an idea or a mathematical formula. The diagram on page 15 is a model of Earth s internal structure. Comparing the layers of Earth to the layers of a hard-boiled egg is also a model. Scientists use models for a number of reasons. Here are some ways in which models are used: to represent an object that is too small or large to be directly observed to show how the sizes of the parts of an object are related to show how objects affect each other to show how objects change over time All models have advantages and limitations. A hard-boiled egg and the diagram on page 15 are both useful for learning about Earth s internal structure, which cannot be directly observed. However, as a model of Earth, a hard-boiled egg has limitations because it is not very detailed. The diagram has much greater detail but is limited by being two-dimensional. Also, it shows each of Earth s layers as having exactly the same thickness throughout, but the thickness of the layers can vary. Think of another way to model Earth s structure. Your model should show the inner core, outer core, upper mantle, lower mantle, and crust. Describe your model below. Identify at least one advantage of your model. Identify at least one disadvantage of your model. 17

7 Lesson Review 1. Which layer of Earth consists mostly of iron? A. continental crust B. oceanic crust C. mantle D. core 2. Which of these layers makes up most of Earth s mass? A. continental crust B. oceanic crust C. mantle D. core 3. On a cross-sectional diagram of Earth, you would label the center of the planet as the A. inner core. B. outer core. C. mantle. D. crust. 4. Which layer of Earth is soft and somewhat fluid, like a very thick liquid? A. the asthenosphere B. the lithosphere C. the crust D. the inner core 18 Chapter 1: Earth Science