1. Stream Erosion Running Water Energy The water cycle
Most effective agent in wearing down the surface of the earth
From the sun… Powers the running water.
One of earths many cycles it is energized by the sun and circulates all of the earths life giving water.

3. Bedrock Breakup Occurs in 2 ways.
Mechanical means– Using sand gravels and small rocks the water grinds at the bedrock. Boulders are also used as cutting tools.
This grinding action is called Abrasion.
Abrasion—also causes the cutting tools to be worn down. Especially at their edges.

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

5. Chemical Means--
Consists of dissolving soluble minerals limestone and marble and sandstones that are held together with calcite cements.
Rivers flowing over such rocks form pits and holes in the bed rock.

6. Transportation
Rivers carry rock materials in 3 ways.
1. Solution– dissolved materials from bedrock. Ex. Calcium , magnesium
2. 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.
3. Bed load– Sediment moved along the stream bottom. Ex large cobbles and boulders.

8. Load Of the stream
Estimate what percent of the load of the stream is solution suspension and bed load.
Solution 25%
Suspension 50%
Bed Load 25%
Note– in General the suspended load increases with human activity.

9. Carrying Power
Discharge
Is indicated by both the total amount of sediment in the stream and by the particle size being moved.
The carrying power 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.
Expressed in CFS
Cubic feet per second.

10. Waterfalls and River Deposits
Potholes
As sand –pebbles and small boulders swirl around in the turbulence of a stream they grind deep oval holes into the stream bed.
Very large potholes are called plunge pools. And form through abrasion or dissolving of minerals.
Found at the base of waterfalls.

11. Waterfalls
NOTE
Occur for many reasons
River may flow over hard rock onto a softer one.
Glaciers erode one valley deeper then others coming into it.
Intrusions of igneous rock
Rapids and waterfalls are only temporary features of streams.

12. Harder Rock. More Resistant
Softer Rock

14. Undermining
Erosion of the base of the water fall leaves an overhang that is susceptible to falling off.
From time to time pieces break off the top of the fall and thus it recedes farther upstream.

15. Meanders
A series of broad curves in the stream bed.
Form when water moves slowly across a wide flood zone.
Also forms oxbow lakes and cutt offs from the river channel.

16. Creation of a Meander and cut offs and ox bow lakes.
Flow direction

17. Formation of Meanders

18. Point bar deposits

19. Formation of an Oxbow

20. Cut bank erosion
Point bar deposits }
Meander loop

23. River Deposition Speed of the river
Dictates how much and what size sediments fall out of the moving water.
Greatest loss of speed is when a river flows into a standing body of water. Or the water source is cut off.
Identify an example in nature when a river would loose water.

24. Answer: Loss of both discharge and speed
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?

25. Deltas - Distribution Systems

27. Alluvial Fans Transition in speed.

28. Assignment: Complete the following.
Explain How running water gets its energy from the sun.
Describe ways– in which running water breaks up bedrock. And how running water transports rock material.
Discuss the relationship between stream speed, discharge and carrying power.
Draw a diagram and explain how a waterfall occurs and how it migrates.
Explain the origin of the following: use a diagram to help you in your explanation.
Meanders, flood plains, cut offs, oxbow lakes, Deltas and alluvial fans.

29. The River Valley The “V” shape
“V” shaped valleys are typical of young streams and river systems.
They occur this way due to the fact that young streams tend to flow at higher speeds which easily scour the stream bed.
Steep valleys are called canyons, gorges, or chasms.
How long does it take to cut a deep canyon?

30. Base Level
Depends…
Kind of bed rock.
The amount of water.
The amount of sediments.
A stream con not cut its bed any lower than the level of the stream river or body of water into which it flows.
Ex. Streams that flow into the ocean the base level is sea level.
What would the Boise river’s “base level be”?

31. As a stream approaches its base level, the slope of the streambed and the speed of the stream decreases.
As a result the streambed weathers slower and slower.
At the same time the valley walls are being eroded and weathered by tributary streams.
The Final result is a wider river valley.
If vegetation is removed by natural or man caused methods this sets up a dangerous situation in nature.

32. Drainage Basin
Or water shed. Includes all the land that drains into the river, either directly or through its tributaries.
What is the largest single drainage basin in the US???
Mississippi River drainage Basin.
What is the largest basin in the world?

35. Erosion Poster Guidelines
Bold Title
Catchy subtitle
Include five topics about your type of erosion
Three diagrams illustrating agent processes
Colored sketches of.
Must have explanations on the following:
Mechanical vs. Chemical Weathering
and
Stream Erosion or
Wind Erosion
Glacier Erosion

36. Erosion Poster Project
Black Textbook-
Streams- pg.168
Glaciers- pg. 190
Wind- pg. 210
Red Textbook-
Streams- pg. 272
Glaciers- pg. 291
Wind- pg. 301

37. Stream Carrying Capacity Review
Black Text Book Pg ,6 Pg , 15 Pg ,17,19