Wind and Wave Erosion

How is wind abrasive?

• It carries sand grains that grind and scour anything that they hit.

What is Loess and how does it form?• It can be 1m to 100m deep. • Made of mineral & rock

particles. • It is wind-carried sediment &

when dropped, it will hold together so well that when it erodes, it splits off vertically to form cliff-like slopes.

• Main deposits of loess in the U.S. include Mississippi & Missouri river valleys.

What is a sand dune?

• Sand dunes - hills of sand deposited by wind. They form when the sand piles up against shrubs, boulders, or other substances.

How does a Sand Dune Migrate?

• When wind blows against the windward side (side facing into the wind) of a dune, some of the surface sand is carried over top & falls on the leeward side (side facing against the wind)

Types of Sand dunes• 1. Barchans – crescent-shaped & the ends of a

barchan point downwind.

Types of Sand dunes• 2. Transverse – Where sand is more abundant,

long continuous sand ridges form at right angles to the wind.

• Found on beaches.

Types of Sand dunes• 3. Parabolic – (u-shaped) dunes often form

around blowouts. Unlike barchans, the open ends of parabolic dunes face upwind.

• Found on beaches.

Types of Sand dunes• 4. Longitudinal – Form in desert regions with

lots of sand. These dunes are long, straight ridges that are parallel to the general wind direction.

Draw a wave and label its parts (Crest, Trough, Height)

How do swash and backwash work together?

• Swash - the motion of water up the beach.• Backwash – the motion of water running back

down the beach

What is a longshore current? How does it affect someone swimming at the beach?• It runs parallel to shore. It moves people

down the beach.

What is a rip current? Why is it dangerous?

• Strong surface currents that flow away from the beach. They can reach up to 5 km/hr. & carry you away from shore.

Describe the process of a sea cliff turning into a sea stack. (4 parts)

• 1. Sea cliff - waves cut out rock & make a notch

• 2. Sea cave - notch will deepen & make a hole

• 3. Sea arch – waves cut through walls of sea caves to make an arch

• 4. Sea stacks – roof of sea arch falls into water

What is a sandbar?

• A sandbar is a bar of sand formed by ocean currents depositing sand near the shore underwater

What is a spit?

• A sandbar attached at one end to the shoreline.

What is a hook?

• A spit with a curved end

What is a barrier island?

• Barrier islands are sandbars not attached to land or the shoreline and are above water

What is a tombolo?

• A tombolo is a bar of sand that joins an island to the mainland.

What is a bay mouth bar?• A bay mouth bar is a spit that completely

closes access to a bay, thus sealing it off from the main body of water.