Transcript Slide 1
Chapter 9 - Section 3, 4, 5, and 6 How Water Erodes Most sediment washes or falls into a river as a result of mass movement and runoff. Other sediment erodes from the bottom or sides of the river. Streams carry sediment in several ways. Erosion and Sediment Load A river’s slope is usually greatest near the river’s source. As a river approaches its mouth, its slope lessens. Sediment on the Move The speed, or velocity, of a stream affects the size of the sediment particles the stream can carry. Sediment on the Move Reading Graphs: What variable is shown on the x-axis of the graph? Stream velocity Sediment on the Move Reading Graphs: What variable is shown on the y-axis of the graph? Diameter of sediment particles Sediment on the Move Interpreting Data: What is the speed at which a stream can move coarse sand? Small pebbles? Large boulders? About 50 cm/sec; about 90 cm/sec; about 800 cm/sec Sediment on the Move Predicting: A stream’s speed increases to about 600 cm per second during a flood. What are the largest particles the stream can move? Small boulders Sediment on the Move Developing Hypotheses: Develop a hypothesis that states the relationship between the speed of a stream and the size of sediment particles it can move. The faster the speed of the flowing water, the larger the particles the stream is able to move. Erosion and Sediment Load The speed of a river varies from the inside edge to the outside edge. As a result river erodes sediment from its banks on the outside curve and deposits sediment on the inside curve. Building Vocabulary Key Terms: Examples: energy Energy is the ability to do work or cause change. potential energy Potential energy is the energy that is stored and waiting to be used later. kinetic energy Kinetic energy is the energy an object has due to its motion. Key Terms: load The amount of sediment that a river carries is its load. friction Friction is the force that opposes the motion of one surface as it moves across another surface. turbulence Instead of moving downstream, the water moves ever which way in a type of movement called turbulence. abrasion Abrasion is the wearing away of rock by a grinding action. How Glaciers Form and Move A continental glacier is a glacier that covers much of a continent or large island. How Glaciers Form and Move During the last ice age, a continental glacier covered most of northern North America. Valley glaciers are created as snow that falls in the mountains slides into the valley. Over thousands of years the snow builds up forming ice that slides down the valley because of gravity. Icebergs are formed when huge chunks of the front edge of the glacier fall off when glaciers meet a body of water. The glacier is resembles a frozen river flowing out of the mountains. As a glacier moves down the mountian, it freezes to the bottom of the valley and breaks pieces of bedrock from the ground in a process called “plucking”. Pieces of bedrock plucked from the valley gradually make it to the top of the glacier making the ice look dirty. Like a bulldozer, the glacier moves huge pieces of rock from the mountain. After the glacier melts and recedes the left over rocks look out of place. Rock left behind by a glacier that has melted is called “Till”. These long scrape marks from glacial abrasion are evidence that a glacier moved over this area. More long scrape marks from glacial abrasion . Additional evidence that a glacier moved over this area. How Glaciers Shape the Land Erosion by glaciers can carve a mountain peak into a sharp horn and grind out a V-shaped valley to form a Ushaped valley. How Glaciers Shape the Land As glaciers advance and retreat, they sculpt the landscape by erosion and deposition. Question What kinds of glaciers are there? How do glaciers shape the land? Answer Valley glaciers and continental glaciers By erosion and deposition Erosion by Waves Waves shape the coast through erosion by breaking down rock and transporting sand and other sediment. The energy in waves comes from wind that blows across the water’s surface. As the wind makes contact with the water, some of its energy transfers to the water. Erosion and deposition create a variety of features along a coast. Deposits by Waves Waves shape a coast when they deposit sediment, forming coastal features such as beaches, spits, and barrier beaches. The sediment on a beach usually moves down the beach after it has been deposited. Waves usually hit the beach at an angle instead of straight on. These angled waves create a current that runs parallel to the coastline. As waves repeatedly hit the beach, some of the beach sediment moves down the beach with the current, in a process called longshore drift. How Wind Causes Erosion Wind erosion moves sediment particles of different sizes in the three ways. Wind Deposition Wind erosion and deposition may form sand dunes and loess deposits.