Topography: Topography PowerPoint Presentation: T opography is the shape of the land. An area ’ s topography may be flat,sloping, hilly, or mountainous. The topography of an area is determined by the area ’ s elevation, relief, and landforms. The height above sea level of a point on Earth ’ s surface is its elevation. The difference in elevation between the highest and lowest parts of an area is its relief. PowerPoint Presentation: A landform is a feature of topography formed by the processes that shape Earth ’ s surface. All landforms have elevation and relief. A large area of land where the topography is similar is called a landform region. The topography of the United States includes many different landform regions. PowerPoint Presentation: There are three main types of landforms: plains, mountains, and plateaus. A plain is a landform made up of flat or gently rolling land with low relief. A plain that lies along a seacoast is called a coastal plain. Coastal plains have both low elevation and low relief. A plain that lies away from the coast is called an interior plain. Although interior plains have low relief, their elevation can vary PowerPoint Presentation: A mountain is a landform with high elevation and high relief. Mountains usually occur in a group called a mountain range. A mountain range is a group of mountains that are closely related in shape, structure,or age. PowerPoint Presentation: A landform that has high elevation and a more or less level surface is called a plateau. A plateau is rarely perfectly smooth on top. Streams and rivers may cut into the plateau ’ s surface. The Four Spheres: The Four Spheres Scientists divide Earth into four spheres: the lithosphere, hydrosphere, atmosphere, and biosphere. Earth ’ s solid, rocky outer layer is called the lithosphere. The Four Spheres: The Four Spheres The outermost sphere is the atmosphere, the mixture of gases that surrounds the planet. Earth ’ s oceans, lakes, rivers, and ice form the hydrosphere. Most of the hydrosphere consists of the salt water in the oceans. The Four Spheres: The Four Spheres All living things — whether in the air, in the oceans, or on and beneath land — make up the biosphere. The biosphere extends into each of the other spheres. The Four Spheres: The Four Spheres The lithosphere is made up of the continents as well as smaller landmasses called islands. The lithosphere even extends under the entire ocean floor. The Lithosphere: The Lithosphere Earth is made up of three layers. The core is the center of the Earth. A thick layer called the mantle surrounds the core. The crust is the thin, outer layer. The crust is made up of hard material called rock . Geology is the study of Earth. Scientists who study Earth are called geologists.