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Transcript
Weathering and Soil Formation Table of Contents Rocks and Weathering How Soil Forms Soil Conservation Weathering and Soil Formation - Rocks and Weathering Chemical Weathering As weathering breaks apart rock, the surface area exposed to weathering increases. Weathering and Soil Formation - Rocks and Weathering Which Weathered Faster? The graph shows the rate of weathering for two identical pieces of limestone that weathered in different locations. Weathering and Soil Formation - Rocks and Weathering Which Weathered Faster? Reading Graphs: What does the x-axis of the graph represent? Time in years Weathering and Soil Formation - Rocks and Weathering Which Weathered Faster? Reading Graphs: What does the y-axis of the graph represent? The thickness of stone lost to weathering Weathering and Soil Formation - Rocks and Weathering Which Weathered Faster? Reading Graphs: How much thickness did Stone A lose in 1,000 years? How much thickness did Stone B lose in the same period? Stone A lost about 8.5 millimeters; Stone B lost slightly more than 4 millimeters. Weathering and Soil Formation - Rocks and Weathering Which Weathered Faster? Drawing Conclusions: Which stone weathered at a faster rate? Stone A weathered at a faster rate. Weathering and Soil Formation - Rocks and Weathering Which Weathered Faster? Inferring: Since the two identical pieces of limestone weathered at different rates, what can you infer caused the difference in their rates of weathering? They were exposed to different climate conditions. Weathering and Soil Formation - Rocks and Weathering Relating Cause and Effect A cause makes something happen. An effect is what happens. As you read, identify the causes of chemical weathering. Write them in a graphic organizer like the one below. Causes Oxygen Effect Water Acid rain Chemical weathering Weathering and Soil Formation - Rocks and Weathering More on Weathering Click the PHSchool.com button for an activity about weathering. Weathering and Soil Formation End of Section: Rocks and Weathering Weathering and Soil Formation - How Soil Forms What Is Soil? Loam, a type of soil, is made up of air, water, and organic matter as well as materials from weathered rock. Weathering and Soil Formation - How Soil Forms What Is Soil? Soil particles range in size from gravel to clay particles too small to be seen by the unaided eye. The sand, silt, and clay shown here have been enlarged. Weathering and Soil Formation - How Soil Forms The Process of Soil Formation Soil forms as rock is broken down by weathering and mixes with other materials on the surface. Soil is constantly being formed wherever bedrock is exposed. Weathering and Soil Formation - How Soil Forms Soil Layers Activity Click the Active Art button to open a browser window and access Active Art about soil layers. Weathering and Soil Formation - How Soil Forms Soil Types Scientists classify the different types of soil into major groups based on climate, plants, and soil composition. Weathering and Soil Formation - How Soil Forms Living Organisms in Soil Some soil organisms make humus, the material that makes soil fertile. Other soil organisms mix the soil and make spaces in it for air and water. Weathering and Soil Formation - How Soil Forms Building Vocabulary A definition states the meaning of a word or phrase by telling about its most important feature or function. Carefully read the definition of each Key Term and also read the neighboring sentences. Then write a definition of each Key Term in your own words. Key Terms: soil loam subsoil soil horizon bedrock litter humus topsoil decomposer fertility Examples: Soil that is horizon, the weathered material on Earth’s The Soil B is loose, made often up of called aboutsubsoil, equal parts usually of clay, consists sand, surface in called which plants canwashed grow. down from the A and of clay siltand is otherloam. particles horizon, but little humus. A soil horizon a layer that differs in Bedrock is the is solid layerofofsoil rock beneath thecolor soil. and As plants shed they form a loose texture from theleaves, layers above or below it. layer called Humus is a dark-colored substance that forms as litter. The horizon is made up decay. of topsoil, a crumbly, dark plantAand animal remains Decomposers are organisms that break the remains brown soil that is a mixture of humus, clay, and other The fertility of soil is a measure of how well the soil of dead organisms into smaller pieces and digest them materials. supports plant growth. with chemicals. Weathering and Soil Formation - How Soil Forms Soil Click the Video button to watch a movie about soil. Weathering and Soil Formation End of Section: How Soil Forms Weathering and Soil Formation - Soil Conservation Soil Damage and Loss Wind erosion is one cause of soil loss. For example, wind erosion contributed to the Dust Bowl on the Great Plains. The Dust Bowl ruined farmland in western Oklahoma and parts of the surrounding states. Wind blew dry particles of soil into great clouds of dust that traveled thousands of kilometers. Weathering and Soil Formation - Soil Conservation Previewing Visuals Before you read, preview Figure 13, “The Dust Bowl”. Then write two questions that you have about the photo and map in a graphic organizer like the one below. As you read, answer your questions. The Dust Bowl Q. Where was the Dust Bowl? A. The Dust Bowl was in western Oklahoma and parts of the surrounding states. Q. What caused the Dust Bowl? A. Farming practices exposed the soil so that in times of drought the topsoil quickly dried out, turned to dust, and blew away. Weathering and Soil Formation - Soil Conservation Links on Soil Conservation Click the SciLinks button for links on soil conservation. Weathering and Soil Formation - Soil Conservation Soil Conservation Click the Video button to watch a movie about soil conservation. Weathering and Soil Formation End of Section: Soil Conservation Weathering and Soil Formation Graphic Organizer Soil Horizons Bedrock begins to weather The C horizon forms as bedrock breaks apart. The A horizon develops from the C horizon where plants grow in it. The B horizon develops as clay and minerals wash down from the A horizon. Weathering and Soil Formation End of Section: Graphic Organizer