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

Erosion by Sea

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

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

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

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

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

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

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

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

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.

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

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.

Sea Cave

Sea Arch

Sea Stack

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. http://www.youtube.com/watch?v=5tU_g-sGFJI&feature=related

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

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.

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.

Emergent Coastline