Water Erosion “We’re changing Earth’s Surface!”

A. Stream Erosion 1. Running Water 2. Energy 3. The water cycle -Most effective agent in wearing down the surface of the earth - From the sun… Powers the running water. - energized by the sun and circulates all of the earths life giving water.

4. Bedrock Breakup -Occurs in 2 ways. a. Mechanical means– Using sand, gravel and small rocks the water grinds at the bedrock. Boulders are also used as cutting tools. 1.) This grinding action is called Abrasion.

Cutting Tools can be very small and as big as cars.

b. Chemical means- dissolving soluble minerals.

5. Transportation -Rivers ability to move material: a. Solution– dissolved materials from bedrock. (25% of stream) b. Suspension– includes clay, silt, and fine sand. Although these materials are heavier than water they are stirred up and kept from settling on the bottom by the water moving. (50% of stream) c. Bed load– Sediment moved along the stream bottom. (25% of stream). Ex large cobbles and boulders.

6. Carrying Power 7. Discharge -Is indicated by amount of sediment and the particle size being moved. a. depends upon the speed of the stream and its discharge. -Is the volume of water flowing past a given point in the stream at a given time. a. Expressed in CFS (Cubic feet per second)

B. Parts of a Stream 1. Flood Plain - When a river swells and floods and covers part of the valley floor.

2. Waterfalls - River may flow over hard rock onto a softer one.

3. Meanders -A series of broad curves in the stream bed. 1.) Form when water moves slowly across a wide flood zone. 2.) Also forms oxbow lakes- U shaped cut off of the stream

Flow direction

Formation of Meanders

Point bar deposits

Cut bank erosion Point bar deposits } Meander loop

Formation of an Oxbow

4. River valleys -V-shaped: cutting into floor & walls and are worn away. a. Steep valleys create canyons

Grand Canyon

C. River Deposition Why streams & rivers deposit sediment. 1. Low slope 2. Bed widens 3. Meets obstruction 4. Reaches a lake or sea

This is a photo of a car buried in flood sediments. Question : Why does a river leave so much sediment on its valley floor after a flood? Answer: Loss ofboth dischargeand speed

2. Delta- fan shaped deposit formed at the mouth of a stream

3. Alluvial Fans- sloping deposits where a mountain stream reaches land.

If the Mississippi changes course again, what will happen to the City of New Orleans?

Drainage Basin  All the land that drains into a river

Erosion Poster Guidelines  Bold Title  Catchy subtitle  Include five topics about your type of erosion  Three diagrams illustrating agent processes  Colored  Sketch or create digitally  Rough draft must be done prior to final poster. This rough draft will be attached to the poster and is worth 20 points.  Must be done on poster board paper no smaller than 12”x 18” furnished by yourself Erosion Types: Mechanical vs. Chemical Weathering Stream Erosion Wind Erosion Glacier Erosion

Erosion Poster Project  Red Textbook  Streams: page 272  Chemical vs. Mechanical weathering: page 238  Glaciers: page 291  Wind: page 301