5-3 Notes Waves and wind Erosion

Think About… How do you think these pillars of rock formed?

Waves and Currents The rock pillars were formed by constant action of waves slowly wearing the rock away.

Waves and Currents In the future, waves will most likely wear away the pillars completely.

Waves and Currents Waves are powered by wind and can wear away rock and move thousands of tons of sand.

Shorelines High, rocky coasts tend to get worn AWAY by waves, while low coastlines are often BUILT UP.

Shorelines When a stream flows into an ocean or lake, it deposits sediment near its mouth.

Shorelines This sediment mixes with the sediment formed by waves crashing against the shore.

Shorelines Waves and currents move this sediment along the shore, building up beaches.

Shorelines Longshore drift: the zigzag movement of sand along a beach.

Shorelines Waves hit the beach at an angle due to the direction wind is blowing.

Shorelines Gravity then pulls the sand straight back down to the water

Shorelines This process eventually shifts the sand down the beach in a zigzag pattern.

Shorelines Longshore current: movement of water along a shore as waves strike the shore at an angle.

Shorelines The direction of the longshore current can change as the direction of the waves striking the shore changes.

Sandbars and Barrier Islands Longshore currents often deposit sand along shorelines.

Sandbars and Barrier Islands Sometimes the sand can build up to form a sandbar-a completely or partially submerged ridge of sand.

Sandbars and Barrier Islands Spit- A sandbar that has built up above the water’s surface and is joined to land at one end.

Sandbars and Barrier Islands Barrier islands-long narrow islands that develop parallel to a coast (start out as sandbars).

Sandbars and Barrier Islands Barrier islands get their name from the fact that they create a barrier between ocean waves and the shore of the mainland.

Wind Shapes Land Wind has the power to transport and deposit sediment. Wind is less powerful than water but it still shapes landforms, especially in dry regions or regions with few plants.

Wind Shapes Land Wind can: Build up dunes Deposit layers of dust Make a land surface as hard as pavement

Dune Formation Dune-a mound of sand built up by wind.

Dune Formation Even a light breeze can carry dust.

Dune Formation A moderate wind can roll and slide grains of sand along a beach.

Dune Formation Only a very strong wind can pick up and carry sand particles.

Dune Formation When the wind dies down or hits something (e.g. a cliff or hill) it drops the sand.

Dune Formation Over time, the sand builds up to create dunes.

Dune Formation Some dunes start out as ripples that grow larger.

Dune Formation Others form as wind-carried sand settles around a rock, log, or other obstacle.

Dune Formation Dunes vary greatly in size and shape and can reach heights of 300 m!

Dune Formation Some dunes are curved; others are straight.

Dune Formation There is usually a gentle slope on the side facing the wind and a steep slope on the side facing away from the wind.

Loess Wind also changes the soil over large regions of Earth by depositing dust.

Loess A strong windstorm can move millions of tons of dust.

Loess Loess: deposits of very fine wind-blown sediment. (pronounced LOH-uhs)

Loess In some regions, deposits of loess have built up over thousands or even millions of years.

Loess Loess is a valuable resource because it forms good soil for growing crops.

Loess Loess covers about 10% of Earth’s land surface.

Desert Pavement Wind can shape land surfaces by removing dust. When wind blows away all the smallest particles from the soil, it leaves behind a hard layer of stone and gravel.

Desert Pavement This is called desert pavement because it looks like cobblestone.

Review 1. In which of the following areas is wind a major erosion agent? A. a grassy field B. an area covered with pine trees C. sand dunes in the desert D. a hillside covered with plant life

Review 2. A dune is a sand mound built up primarily by A. gravity B. running water C. glaciers D. wind

Review 3. Strong winds can transport large quantities of A. gravel B. wet sand C. dry sand D. clay