4Longshore DriftCoin moved up at an angle and then straight down…like longshore drift.Beach=book surfaceSand=the coinWave=movement of your finger
5Longshore: drift vs current Longshore drift is the movement of SAND.Longshore current is the movement of WATER.Both cause beaches to form, reform or disappear.
6Beach sand? Where does beach sand come from to form the beaches? They come from SEDIMENT brought to the shore by rivers and from rocks eroded (weathered) along the shoreline.Remember 5.2?????
7Why don’t the beaches stay put? Waves and currents move sand along a beach.When waves hit the beach at an angle, they carry sand up and onto the shore in this direction.The movement of waves that strike the shore at an angle is longshore current.Once the waves have washed up, they are then pulled back by gravity. This causes a zigzag movement of sand (longshore drift).This causes sand to move gradually down a beach. This causes sand to shrink in some areas and grow in others.
8What else can wind do??IF wind not only carries and moves sand from one place to another…….if it also carries sediment….THEN it will deposit LOESS—which is wind-blown sediment.Loess is very good soil for growing plants and crops.
9Just the small stuff……… Sometimes WIND just picks up the small sand, dust and silt and leaves the gravel and rocks.These not removed rocks and gravel in a desert are called: Desert Pavement
10Sandbars and Barrier Islands Which one ends up above the surface of the water?Answer: The Barrier IslandFrom which structure do both spits and barrier islands form?Answer: Sandbars
11Chapter Review page 1631. What kinds of landforms do longshore drift and longshore currents produce? (Wind + Water)Sandbars, Barrier Islands, Spits and beaches!
12Chapter Review page 163 How do dunes form? They form from strong winds piling up sand in mounds or hills.Some dunes can be 300 meters high!What must be available? Strong winds and loose sand!
13Chapter Review page 1633. How does loess form and why is it important?Loess forms as winds deposit fine sediments from elsewhere.It can form thick deposits of very fertile soil.
14Chapter Review page 1634. Is longshore drift the cause or effect of a longshore current?Answer:Longshore drift is the effect of a longshore current.Longshore drift is the movement of sand, which is caused by longshore current (which is the force of the water moving in a direction).
15Chapter Review page 1635. What effect would a barrier island have on the shoreline of the mainland?Answer:It would lessen the force of the waves on the main shore, especially during storms or hurricanes.
16Chapter Review page 1636. The south and east shores of Lake Michigan have large areas of sand dunes, but the north and west shores do not. Write a hypothesis that explains why.IF the north and west shores do not have dunes, THEN the conditions for dune formation is not there BECAUSE the wind is blowing sand toward the water and not inland (where dunes can develop).