1. Unit 1: Land and Water Forms Wearing Down Landforms Wind and Waves
World Geography
Unit 1: Land and Water Forms
Wearing Down Landforms Wind and Waves

2. Erosion by Sea

3. Wind Erosion
Wind does not have the energy to erode or transport large rock particles like water or glaciers.
It works mostly on sand and fine sediment
It’s effects are most commonly seen in deserts and on beaches
Works in two main ways
Deflation
Abrasion

4. Deflation
Deflation: The hollowing of a piece of land by wind removing small particles.
Deflated landscapes appear as jagged deserts, with bare and exposed bedrock or a dense pavement of stones and gravel
A desert with these features is known as a hamada

5. Abrasion
Abrasion: When wind-borne particles blow against a surface, sandblasting and wearing them away.

6. Wind Deposition
Wind may carry particles for thousands of kilometers, but they must come down
Eventually particles are deposited in a particular type of desert known as an erg
Erg: areas of extensive dunes, mounds, and ridges of sand

7. Ergs The greatest erg desert is the Sahara Desert
The most common landscape features of an erg are sand dunes.
Sand Dunes: Cresent or triangular shaped piles of sand that form when slowing wind drops particles of sand
Barchan – Crescent shaped dune, with horns pointing into the wind

8. Wave Erosion
As wind passes over water it transfers energy through friction
This transfer of energy creates waves
Where waves meet land erosion occurs

9. Wave Movement and Direction
To understand wave erosion you must understand two important concepts
Wave Refraction
Longshore Drift

10. Wave Refraction
Waves generally form in long ridges that are perpendicular, at 90o’s, to the winds direction.
As waves approach the shore they bend to line up parallel to the shoreline.
The refraction occurs because as the waves enter the shallow water near the shore they loose energy.
As a result of wave refraction all of the energy from the wave is concentrated on the headland
Headland: portions of land that reach out into the ocean

11. Longshore Drift
As waves move along a coast they move eroded sand and gravel along the shoreline.
Longshore drift occurs because the waves hit the coast at angles, pushing the sediment along the shore.

13. Spit
Spit: A ridge of sand running away from the coast, usually with a curved seaward end. Spits grow in the prevailing direction of longshore drift. Their ends are curved by the action of waves coming from different directions

14. Water Landforms
Sea Cave: A large, natural hollow in a headland caused by wave erosion
Sea Arch: The feature which results when two caves occuring on either side of a headland are cut until they meet.
Stack: An isolated islet or piller of rock standing up from the sea bed close to the shore.

15. Sea Cave

16. Sea Arch

17. Sea Stack

18. How Water Landforms Are Created
Water wears away at a headland forming sea caves on two sides.
When the Caves meet they form an arch.
When an arch collapses it forms a Stack.

19. The Straightening Out of Irregular Coastlines
Depends on how coast was formed.
Glaciation and rebound
Decreasing sea level
Sea level rises or plates cause seafloor to sink

20. Embayed Shoreline Drowned or submerged coastline. Sea level rises.
Often through plate movement
What were once river valleys submerge making irregular coastline.
Erosion works quickly on this new land and straightens it out.

21. Clift and Terrace (emergent coastline)
Result of rising land levels
As ice melts a great weight is lifted off of the land causing it to rebound
This occurs slowly, and is still happening.

22. Emergent Coastline