8th Grade The Dynamic Earth (Module E) Unit 1 Lesson 3 Erosion and Deposition by Water

Flowing water changes Earth’s surface Unit 1 Lesson 3 Erosion and Deposition by Water Flowing water changes Earth’s surface Erosion is the process by which sediment and other materials are MOVED from one place to another. Sediment: tiny grains of broken-down rock. Deposition is the process by which eroded material is DROPPED. (usually downstream) Happens when pull of gravity is more than force of flowing water or wind Copyright © Houghton Mifflin Harcourt Publishing Company 2

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1. Gradient – change in elevation over a certain distance Unit 1 Lesson 3 Erosion and Deposition by Water Factors that control how much sediment a stream moves - 1. Gradient – change in elevation over a certain distance “Steepness” or “slope” Steep gradient = more energy to carry soil http://www.riverpartners.org/img/riparian-ecology/watersheds_530.jpg Copyright © Houghton Mifflin Harcourt Publishing Company 4

2. Load - the materials carried by a stream. Unit 1 Lesson 3 Erosion and Deposition by Water 2. Load - the materials carried by a stream. The size of the particles in a stream’s load is affected by the stream’s speed. Fast-moving streams = large particles and high erosion rate. Slow-moving streams = smaller particles and low erosion rate. Copyright © Houghton Mifflin Harcourt Publishing Company 5

3. Discharge - amount of water that a stream carries Unit 1 Lesson 3 Erosion and Deposition by Water 3. Discharge - amount of water that a stream carries Increases after large storms and rapid snow melts. As a stream’s discharge increases, its erosive energy, speed, and load increase. Do the math! Page 31 Copyright © Houghton Mifflin Harcourt Publishing Company 6

What do you think? – read pg. 32-33 Unit 1 Lesson 3 Erosion and Deposition by Water What landforms can streams create? What do you think? – read pg. 32-33 channel - the path that a stream follows canyons and valleys Copyright © Houghton Mifflin Harcourt Publishing Company 7

When rivers flood, sediments get deposited over flooded land Unit 1 Lesson 3 Erosion and Deposition by Water When rivers flood, sediments get deposited over flooded land floodplain - flat area formed from many layers of deposited sediment. (Deposition!) often very fertile – sediment contains nutrients Meander video demo with sand - Copyright © Houghton Mifflin Harcourt Publishing Company 8

Curves and bends in a stream channel are called meanders. Moving water erodes the outside banks and deposits sediment along the inside banks.

sometimes a meander can be cut off, forming an oxbow lake.

- Water Erosion Watch Grand Canyon formation video – Science Fusion History Channel resources

delta -fan-shaped pattern of deposited sediment IN WATER Unit 1 Lesson 3 Erosion and Deposition by Water When a stream empties into another body of water, its current slows and it deposits its load. delta -fan-shaped pattern of deposited sediment IN WATER http://www.earthmagazine.org/sites/earthmagazine.org/files/1324689397/i-2ff-7d9-b-18.jpg Copyright © Houghton Mifflin Harcourt Publishing Company 12

alluvial fan - fan-shaped deposit that forms ON DRY LAND. Unit 1 Lesson 3 Erosion and Deposition by Water alluvial fan - fan-shaped deposit that forms ON DRY LAND. Svalbard, in the Norwegian Arctic Copyright © Houghton Mifflin Harcourt Publishing Company 13

What landforms can streams create? Unit 1 Lesson 3 Erosion and Deposition by Water What landforms can streams create? What landforms can you identify in the image below? Explain how each type of landform formed. Copyright © Houghton Mifflin Harcourt Publishing Company 16

Landforms made by groundwater erosion Unit 1 Lesson 3 Erosion and Deposition by Water Groundwater - water located within the rocks below Earth’s surface -Acidic groundwater dissolves rock, forms caves Sinkhole - circular depression when cave roof collapses Stalactites and stalagmites - icicle-shaped deposits from water dripping from cracks in cave’s ceiling Do digital lesson #9 Discovery education cave formation Mammoth Cave (7:51)- https://www.youtube.com/watch?v=FgRKOPz3y8U Cool Cave formation and glaciers BBC - https://www.youtube.com/watch?v=IKZ9EHewjZg Copyright © Houghton Mifflin Harcourt Publishing Company 17

What forces shape a shoreline? Unit 1 Lesson 3 Erosion and Deposition by Water shoreline - place where land and a body of water meet. Ocean waves and currents, or streamlike movements of water, can erode and deposit materials. Waves slow down as they approach a shoreline. Copyright © Houghton Mifflin Harcourt Publishing Company 18

Waves strike headlands (pieces of land that project into the water) with MORE energy (=more erosion) Waves striking areas between headlands have less energy so deposit materials. Unit 1 Lesson 3 Erosion and Deposition by Water Copyright © Houghton Mifflin Harcourt Publishing Company 19

Longshore currents Unit 1 Lesson 3 Erosion and Deposition by Water Currents that travel almost parallel to the shoreline very near shore. -Caused by waves hitting the shore at an angle. -As sand moves down a beach… -upcurrent end is eroded away -downcurrent end is built up Longshore drift animation - https://www.youtube.com/watch?t=1&v=4Tz5FfWq2cg Copyright © Houghton Mifflin Harcourt Publishing Company 20

What forces shape a shoreline? Unit 1 Lesson 3 Erosion and Deposition by Water What forces shape a shoreline? What might this beach area look like in the future? Copyright © Houghton Mifflin Harcourt Publishing Company 21

Coastal landforms made by erosion Unit 1 Lesson 3 Erosion and Deposition by Water The rate at which rock erodes depends on the hardness of the rock and the energy of the waves. Gentle waves - little erosion, strong waves (from storms) - increase rate of erosion. Harder rock slows the rate of erosion - takes more wave energy to break the rock. Soft rock erodes more rapidly. Copyright © Houghton Mifflin Harcourt Publishing Company 22

Some landforms (p. 36 picture) Unit 1 Lesson 3 Erosion and Deposition by Water Some landforms (p. 36 picture) sea cliff - waves erode and undercut rock to make steep slopes. As a sea cliff erodes above the waterline, a bench of rock, called a wave-cut platform, can remain below the waterline. sea caves – waves cut holes into weak or fractured rock More erosion on sea caves makes sea arches and sea stacks. Copyright © Houghton Mifflin Harcourt Publishing Company 23

What coastal landforms are made by erosion? Unit 1 Lesson 3 Erosion and Deposition by Water What coastal landforms are made by erosion? What landforms can you identify in the image below? How did each landform form? Copyright © Houghton Mifflin Harcourt Publishing Company 24

Coastal landforms made by deposition Unit 1 Lesson 3 Erosion and Deposition by Water beach -made up of material deposited by waves and currents. The size and shape of materials on a beach depend on how far the material has traveled, the type of material, and how it is eroded. sandbar - underwater or exposed ridge of sand, gravel, or shell material. barrier island - long, narrow island, (usually made of sand) that forms parallel to the shoreline a short distance offshore. Copyright © Houghton Mifflin Harcourt Publishing Company 25

Living on the Edge – read pg. 39 Unit 1 Lesson 3 Erosion and Deposition by Water Living on the Edge – read pg. 39 Barrier islands are found all over the world. Barrier islands can change shape and be eroded away by tides and large storms. Barrier island erosion can be slowed down by using sandbags and other anti-erosion techniques. Copyright © Houghton Mifflin Harcourt Publishing Company 26