Stream Bed Erosion Bell ringer: Write the question & the full answer 1. In a streambed, where is erosion the greatest? a. On the top b. In the middle c. On the bottom When the mineral composition of a rock changes, its due to a. chemical weathering b. mechanical weathering c. deposition 3. What type of environment contains the greatest rate of chemical weathering? a. cold & dry b. warm & dry c. warm & wet d. cold & wet 4. You notice lots of broad curves in a slow moving river. What stage do you assume the river is in? a. young b. mature c. just beginning 5. What force produces the greatest amount of erosion? Moving water Glaciers Wind 6. Water below Earth’s surface is termed: a. surface water b. water table c. ground water

IV. Wind

A. Wind 1.Conditions 2. Dust storms -Wind erosion and weathering are most effective where sands silts and clays lie loose and dry. Ex. Great desert areas of the world Sahara in Africa and the Mohave SW USA. -Very destructive, strong steady winds lift great amounts of loose silt and clay. Ex. Great Plains 1930s

B. How Wind Causes Erosion the particles must be light and hard. Causes rounding of rocks -The removal of loose rock particles by wind Stronger particles need stronger winds to move . Results: 1.) Desert pavements- area of only heavy rocks 2.) Blowouts- hollow areas 1.Abrasion 2. Deflation B. How Wind Causes Erosion

Blowout

C. Wind Deposition 1. Sand Dunes a. Windward- b. Leeward c. Shape of - Are hills deposited by winds. They form when sand piles up against shrubs. boulders or other obstacles. -Long gentle slope facing the direction the wind is blowing. -Steep slope facing away from the direction the wind is blowing. -Depends on the following. Supply of sand, Strength of wind, Steadiness and amount of vegetation.

Barchan

Transverse

Longitudinal

Star

Star Dune

Dune Migration

C. Wind Deposition 2. Loess Wind deposited sediment a. Sediment is fine silt & clay (creates fertile land)

Loess deposits of the world.