8 Grade The Dynamic Earth (Module E) · 2020. 1. 9. · What landforms can streams create? What do...
Transcript of 8 Grade The Dynamic Earth (Module E) · 2020. 1. 9. · What landforms can streams create? What do...
Unit 1 Lesson 3 Erosion and
Deposition by Water
8th Grade
The Dynamic Earth (Module E)
Copyright © Houghton Mifflin Harcourt Publishing Company
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
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
Copyright © Houghton Mifflin Harcourt Publishing Company
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
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
Unit 1 Lesson 3 Erosion and Deposition by Water
Copyright © Houghton Mifflin Harcourt Publishing Company
What landforms can streams create?What do you think? – read pg. 32-33
• channel - the path that a stream follows
• canyons and valleys
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
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 1 Lesson 3 Erosion and Deposition by Water
• 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
• 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
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 1 Lesson 3 Erosion and Deposition by Water
• alluvial fan - fan-shaped deposit that forms ON DRY LAND.
Copyright © Houghton Mifflin Harcourt Publishing Company
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
Unit 1 Lesson 3 Erosion and Deposition by Water
Copyright © Houghton Mifflin Harcourt Publishing Company
• Groundwater - water located within the rocks below Earth’s surface
-Acidic groundwater dissolves rock, forms caves
• Sinkhole - circular depression when cave roof collapses
Unit 1 Lesson 3 Erosion and Deposition by WaterLandforms made by groundwater erosion
• Stalactitesand stalagmites -icicle-shaped deposits from water dripping from cracks in cave’s ceiling
• Both waves and currents affect the shoreline (place where land and a body of water meet)
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 1 Lesson 3 Erosion and Deposition by WaterErosion and Deposition by the OCEAN
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 1 Lesson 3 Erosion and Deposition by WaterWAVES• waves slow down and bend around
headlands (pieces of land that project into the water) as they approach shoreline
• strike headlands with MORE energy (so more erosion)
• Strike betweenheadlands withless energy(so more deposition)
• 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…
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 1 Lesson 3 Erosion and Deposition by WaterLONGSHORE CURRENTS
-upcurrent end iseroded away
-downcurrent end is built up
What forces shape a shoreline?
• What might this beach area look like in the future?
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 1 Lesson 3 Erosion and Deposition by Water
Copyright © Houghton Mifflin Harcourt Publishing Company
• 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.
Unit 1 Lesson 3 Erosion and Deposition by Water
Some landforms made by erosion (p. 36 picture)
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 1 Lesson 3 Erosion and Deposition by Water
• 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.
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
Unit 1 Lesson 3 Erosion and Deposition by Water
Copyright © Houghton Mifflin Harcourt Publishing Company
• 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.
Unit 1 Lesson 3 Erosion and Deposition by Water
Unit 1 Lesson 3 Erosion and Deposition by Water
Living on the Edge – read pg. 39
Copyright © Houghton Mifflin Harcourt Publishing Company
• 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.