EROSION

1. EROSION Erosion - process by which sediments are obtained and carried away. • it wears away and lowers the surface features of the Earth.

2. Gravity is the driving force for most agents of erosion; It is the force which drives…. • mass wasting • running water • ice (glaciers)

3. 5 AGENTS OF EROSION CAUSED BY GRAVITY OTHERS wind rivers glaciers waves mass wasting

4. 1 – Mass Wasting (mass movement) • erosion and deposition done directly by gravity. examples; • creep, mudslides, avalanches, landslides. La Conchita, CA 1995 landslide  (Courtesy USGS)

5. Creep

6. Slump

8. Two forces are involved in mass wasting; 1 – the downward pull of gravity. 2 – friction – which holds objects in place.

9. Mass movements often occur after heavy rainfall. • the water that soaks into the soil adds mass (downward pull of gravity increases). • the water reduces the amount of friction.

10. 1) Which change would most likely cause soil layer X to increase in thickness? (1) a decrease in slope (2) a decrease in rainfall (3) an increase in biologic activity (4) an increase in air pressure

11. 2) Which event is the best example of erosion? (1) breaking apart of shale as a result of water freezing in a crack (2) dissolving of rock particles on a limestone gravestone by acid rain (3) rolling of a pebble along the bottom of a stream (4) crumbling of bedrock in one area to form soil

12. 3) The block diagram below shows a displacement of rock layers. Which process describes the downward sliding of the rock material? (1) tidal changes (3) mass movement (2) glacial erosion (4) lava flow

13. 4) Unsorted, angular, rough-surfaced cobbles and boulders are found at the base of a cliff. What most likely transported these cobbles and boulders? (1) running water (3) gravity (2) wind (4) ocean currents

14. Type of Weathering Indicate whether the each of the following is an example of Physical or Chemical weathering. 1) wetting and drying 2) oxidation 3) abrasion 4) plant and animal action 5) hydrolysis 6) ice wedging 7) carbonic acid 8) exfoliation physical chemical physical physical chemical physical chemical physical

15. Rates of Weathering A B C D 9) Which sample has the greatest surface area? 10) Which sample has the least surface area? 11) Which sample will weather at the slowest rate? 12) Which sample will weather at the greatest rate? 13) If the samples above were salt, which sample will take the least amount of time to dissolve? 14) If the samples above were salt, which sample will take the most amount of time to dissolve? D A A D D A

16. calcite 15) Which mineral is dissolved by acid? 16) Name two rocks that are composed to the mineral listed in questions 15. 17) Which type of climate will have the greatest amount of chemical weathering? 18) Soil that does not match the local bedrock, because it has been moved into the area from another location is called….. soil limestone marble wet hot transported

17. residual 19) Soil that is similar to the local bedrock, has formed in place and is called…. soil 20) Most of the soil in New York state is soil. 21) An older soil, that contains O, A, B, and C layers is referred to as a soil. 22) What do they call the bedrock, from which a soil is produced? material transported mature parent

18. 2 – RUNNING WATER (rivers) • running water is the most common agent of erosion. • running water is responsible for moving the most amount of material.

19. stream – running water that is confined to a channel. (also river, creek, etc) • permanent streams are those that flow all year.

20. River terms

21. A smaller stream that flows into a larger stream is called a tributary.

22. Drainage patterns A river and all of its tributaries is called a river system. Parallel Dendritic Radial Rectangular Trellis

23. A drainage basin (or watershed) is all the land that drains into the river system.

24. The high land that separates one drainage basin from another is a divide.

25. Continental Divide • the major divide of the United States. • it is located in the Rocky Mountains.

26. Rain falling on the East side of the divide eventually flows into the Atlantic Ocean. • Rain falling on the West side of the divide eventually flows into the Pacific Ocean.

27. 1)The map shows a stream drainage pattern. Arrows show the direction of stream flow.On which landscape region did this drainage pattern most likely develop?

28. 2) The entire land area drained by the Mississippi River system is referred to as a (1) levee (3) meander belt (2) watershed (4) floodplain

29. continental divide

30. 3 Ways in Which streams carry sediment 1 – Solution • mineral matter that has been dissolved from the bedrock (ex calcium). 2 – Suspension • material carried by the river (clay, silt, fine sand). 3 – Bed Load(saltation or traction) • heavier materials that are moved along the stream bed (roll or slide)

32. Velocity of a stream; As the velocity of the river increases… • The amount of material that it can carry will increase. • The size of the largest particle it can carry will increase. SEE ESRT

33. Cave Creek, Arizona Description: Images of flash flooding after a monsoon storm. These storms often occur quickly in desert regions with relatively little soil and plant cover. This road is usually closed for an hour or two several times a year by flash floods. As little as a foot of water can sweep cars downstream, a major cause of flood fatalities in the US.

34. What is the size of the largest particle that a stream can carry if its velocity is…. 0.1 cm/sec = 100 cm/sec = silt pebbles

35. 1) What is the minimum water velocity needed in a stream to maintain the transportation of the smallest boulder? (1) 100 cm/sec (2) 200 cm/sec (3) 300 cm/sec (4) 500 cm/sec

36. 2) A stream flowing at a velocity of 75 centimeters per second can transport (1) clay, only (2) pebbles, only (3) pebbles, sand, silt, and clay, only (4) boulders, cobbles, pebbles, sand, silt, and clay

37. Three Factors that affect Stream Velocity 1 – gradient (slope of the stream). • as gradient increases, velocity increases. 2 – discharge (the volume of water in the stream) • as discharge increases, velocity increases. 3 – channel shape • friction with channel decreases velocity.

38. Gradient (slope) and Velocity

39. Gradient (slope) and Velocity

40. 1) Two streams begin at the same elevation and have equal volumes. Which statement best explains why one stream could be flowing faster than the other stream? (1) The faster stream contains more dissolved minerals. (2) The faster stream has a much steeper gradient. (3) The streams are flowing in different directions. (4) The faster stream has a temperature of 10°C, and the slower stream has a temperature of 20°C.

41. Regions of Maximum Velocity Straight channel • maximum velocity occurs at the center of the stream. diagram high H

42. Meanders (bends or turns in a river) • maximum velocity is on the outside of the curve.

43. diagram high inside outside H

44. A A’ A A’ H outside inside high velocity low velocity erosion B deposition B’ B B’ deep shallow H steep gentle C’ C C C’ H

45. Velocity also varies with depth • Friction, with the stream bed, causes the velocity to decrease. • greatest velocity is just below the surface. diagram H classzone.com

46. 1) The map below shows the path of a river. The arrow shows the direction the river is flowing. Letters A and B identify the banks of the river. The water depth is greater near bank A than bank B because the water velocity near bank A is (1) faster, causing deposition to occur (2) faster, causing erosion to occur (3) slower, causing deposition to occur (4) slower, causing erosion to occur

47. 2) At which two locations is the rate of erosion greater than the rate of deposition? (1) A and B (3) C and D (2) B and C (4) D and A

48. 3) A decrease in the velocity of this stream will most likely cause an increase in (1) the amount of sediment carried by the stream (2) the size of the particles carried by the stream (3) deposition within the stream channel (4) abrasion of the stream channel

49. Evolution of a Stream Intermediate Old Age Young

50. Early Stages (Young) • most energy is used for down-cutting. • forms narrow “V” – shaped valley. • usually a steep slope (gradient). • Contains waterfalls and rapids.