1. Chapter 7: Erosion and Deposition
7.1: Forces wear down and build up Earth’s surface
7.2: Moving water shapes land
7.3: Waves and wind shape land
7.4: Glaciers carve land and move sediments

2. 7.3: Waves and wind shape land
Before, you learned:
Stream systems shape Earth’s surface
Groundwater creates caverns and sinkholes
Now, you will learn:
How wave currents shape shorelines
How wind shapes land
Book, p.158: Pillars of Rock, Port Campbell, Australia:
Why do you think these are left over from large areas of rock?
The pillars are made of hard rock that was among softer or fractured rock that was easier to weather and disintegrate

3. Waves and currents shape shorelines
Port Campbell pillars formed by movement of water
Continuous action of waves breaking against the cliffs
2 cm/year, and still eroding
Force of wave: powered by wind, can wear away rocks and transport sand
Force of wind: can change the look of land

4. Shorelines Can be flat, low, high, steep, rocky, sandy…
High rock cliff: waves crash and wear away bottom rocks
Low coastlines build up
Similar to when a stream flows into an ocean or lake, sediment is deposited near its mouth
This sediment mixes with sediment from waves beating against the coast, building up beaches
Describe movement of sediment and water along the shore:
Longshore drift
Longshore current

5. Shorelines – Longshore drift
Longshore drift: zigzag movement of sand along a beach
Wind blows across water and may hit the shoreline at an angle
Carries sand to shore, and gravity pulls the water and sand back out to the water
The sand gradually moves down the beach
Moves large amounts of sand along a beach: shrink/grow

6. Shorelines – Longshore current
Longshore current: movement of water along a shore as waves strike the shore at an angle
Direction may change from day to day as wave direction changes

7. Oceans, aside Ocean waves are a movement of energy, not water
A cork in water impacted by a wave moves - it rises and falls on the wave but does not move forward
Water waves move energy, not material
A message in a bottle thrown to sea may arrive cross the sea by currents, rather than waves

8. Sandbars and Barrier Islands
Longshore currents can deposit sand along shorelines
This sand builds up to form sandbars
A ridge of sand built up by the action of waves and currents
If the sandbar is built up above the water’s surface and is joined to the land, it is called a “spit”
Strong longshore currents that mostly move in one direction over time build up the sandbar into barrier islands
A long narrow island that develops parallel to a coast
Forms a barrier between the ocean waves and the shore of the mainland
Common along gently sloping coasts: New Jersey, North Carolina, Gulf of Mexico
Constantly change shape

10. Wind shapes land Sand dunes…far from a desert or ocean!
Created by wind:
Dune: a mount of sand built up by wind
Like water, wind can transport and deposit sediment
Especially powerful in dry regions where soil is not held in place (few plants)
Near Lake Michigan

11. Wind Shapes Land Dune formation:
Strong wind picks up and transports sand particles – deposits the sand which builds to dunes
Can start as a ripple then grow larger
Can form as wind-carried sand settles around a rock, log, or other obstacle
Need: strong winds AND constant supply of loose sand
Vary in size an d shape
up to 300 meters (1000 ft), curved, straight, mounds
Typically have a gentle slope facing the wind, and steep on the other side

14. Loess Wind also changes soil by depositing dust
Loess: deposits of fine wind-blown sediment
Can build up over thousands or millions of years
Forms good soil for growing crops
Some deposits 300 meters thick!
Ex: China: deposits are 2 million years old
Central U.S.: between 8-30 m ( ft) deep

15. Desert Pavement Wind can also remove dust
It blows away sand, silt, and gravel, leaving behind a layer of stones and gravel
Called “desert pavement” because it looks like a cobblestone pavement
What remains is too heavy to be picked up by wind

16. Coastline video: http://scienceblips. dailyradar
Videos:

17. Snow Line Elevation and Latitude p.251

18. Mount kenya is very close to the equator
Mount kenya is very close to the equator. Estimate the snow line elevation on mount kenya.
Mount rainier is at 47 degrees north latitude and is 4389 meters tall. Can there be glaciers on mount rainier? If so, estimate the elevation above which the glaciers form.
Mount washington in new hampshire is at 45 degrees north latitude and is 1917 meters tall. Can there be glaciers on mount washington? If so, estimate theeir lowest elevation.
Challenge: temperatures are hotter at the equator than at 28 degrees north latitude. Why is the snow line lower at the equator in Ecuador?