2. Key Concepts 1 Earth’s major systems include the atmosphere, hydrosphere, biosphere, and geosphere. All four major Earth systems interact by exchanging matter and energy. A change in one Earth system affects all other Earth systems. Gravity caused particles to come together to form a spherical Earth. Lesson 1: Spherical Earth

4. Earth’s Formation Earth formed as gravity pulled small particles together that collided, built mass, and collected more particles. As Earth grew, it heated up inside. Its rocks softened and began to flow. Gravity pulled in the irregular surface bumps toward Earth’s center. Earth began to look like a sphere. All objects on or near Earth are pulled toward Earth’s center by gravity.

5. Earth’s Formation: Formation of Layers The force of gravity caused denser materials to sink toward the center of Earth The densest material sank and formed the inner most layer of Earth. The least dense material stayed at the surface of the planet. The materials that had intermediate density formed the middle layers of Earth.

6. Key Concepts 2 Lesson 2: Earth’s Interior Earth’s interior layers include the crust, mantle, and core. By analyzing earthquake waves, scientists have determined that the outer core is liquid and the inner core is solid.

7. Earth’s Layers: Crust The brittle, rocky, outer layer of Earth is called the crust.crust The crust is the least dense layer of the geosphere and much thinner than the other layers. There are two types of crust: Oceanic Crust Crust under the oceans Thin, but more dense Continental Crust Crust under the continents Thick, but less dense

8. Earth’s Layers: Mantle Thick middle layer in the solid part of Earth is the mantle. The rocks in the mantle are denser than crustal rocks. Scientist group the mantle into four different layers: Uppermost Mantle/Lithosphere Rigid and brittle like the crust Asthenosphere Hot, soft melted rock that begins to flow Upper Mantle Solid rock under great pressure Lower Mantle Solid rock under great pressure

9. Lithosphere and Asthenosphere Lithosphere: The rigid outermost layer of the Earth that includes the uppermost mantel and the crust. It is thin below the oceans and thick below the continents Earth’s tectonic plates are large pieces of the lithosphere Asthenosphere: The partially melted portion of the mantle located just below the lithosphere. So hot it behaves like “plastic” Allows the plates of the lithosphere to move because the hotter, plastic mantle material beneath them can flow The interactions between the lithosphere and the asthenosphere help explain plate tectonics

10. Earth’s Layers: Core The dense metallic center of the Earth is the core. The central part of the Earth is made of metal. When the planet was young, these dense materials melted and were pulled toward Earth’s center Scientist group the mantle into two different layers: Outer Core Liquid iron Not rigidly attached Inner Core Solid iron Spins faster than rest of earth The core causes a force field to form around earth.

11. Key Concepts 3 Earth’s major landforms include plains, plateaus, and mountains. Plains have low relief and low elevation. Plateaus have low relief and high elevation. Mountains have high relief and high elevation. Plains, plateaus, and mountains are all found in the United States. Lesson 3: Earth’s Surface