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CHAPTER 8 EROSION.

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Presentation on theme: "CHAPTER 8 EROSION."— Presentation transcript:

1 CHAPTER 8 EROSION

2 Extra Credit Quiz What happens to you when you are tardy 1 or 2 days?
What happens to you when you are tardy 6 or more days? Where do you need to be for Mr. Drennen to consider you on time for his class?

3 Extra Credit Quiz (cont.)
5. What happens to a student if Mr. Drennen notices that they did not complete the warm-up activity? 6. What is now going to happen every time a student feels it is necessary to yell or talk loudly across my room to another student. 7. What happens if you throw anything in Mr. Drennen’s class?

4 Extra Credit Quiz (cont.)
8. What happens to a student who purposely annoys or antagonizes another student in Mr. Drennen’s class? 9. What is now going to happen to any student who talks over Mr. Drennen? 10. What happens if you have a cell phone out in Mr. Drennen’s class?

5 Chapter Eight: Erosion
I. Erosion & Deposition A. Erosion 1. wears away surface materials and moves them from one location to another 2. Agents (causes) of Erosion a) gravity b) glaciers c) wind d) water

6 B. Deposition 1. the more quickly an agent of erosion is moving the more sediments it can carry 2. All agents of erosion drop their load of sediments when their energy of motion decreases (slows down)

7 II. Gravity A. def. force of attraction that exists between all objects B. Mass Movement 1. Gravity alone causes loose materials to move downhill

8 C. Examples of Mass Movement
1. Slump a) mass movement in which loose materials or rock layers slip down a slope b) strong rock lies over weak materials c) the weak material can not hold the rock up so it slides downhill d) will leave a curved “scar” where the slumped materials originally rested e) happens mostly after earthquakes or heavy rains

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10 2. Creep a) sediments slowly inch their way down a hill b) common in areas of freezing & thawing

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12 3. Rockslides a) large blocks of rock break loose & start tumbling b) while falling these rocks crash into other rocks causing them to break loose and fall c) more & more rocks break loose & tumble to the bottom d) rockslides are very fast & destructive. Can happen at any time without warning

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15 4. Mudflows a) usually happen in dry areas where weathering accumulates thick layers of sediment b) when heavy rains fall the water mixes with the dry sediments c) gravity then causes the water & the sediments to move downhill

16 d) when a mudflow reaches the bottom of a slope it loses energy &
deposits its sediments e) the sediments usually spread out into a cone shape

17 Use your notes to answer the following
1. List four agents of erosion 2. What force causes mass movement? 3. List four examples of mass movement? 4. When will an agent of erosion drop its load of sediments?

18 III. Glaciers A. def. a moving mass of ice & snow 1. Form in an area where the snow never melts 2. the snow begins piling up into a thick layer 3. Eventually this thick layer of ice moves & becomes a glacier

19 B. Continental Glaciers
1. Huge masses of ice & snow 2. Ice Age a) 20,000 years ago continental glaciers covered % of the Earth 3. Today are found at the polar regions and Greenland a) only cover 10% of the Earth 4. These glaciers are so thick they can almost bury mountain ranges

20 C. Valley Glaciers 1. Found on mountains where snow does not melt in the summer 2. Form & Grow in the valleys and slide down the mountain 3. Have U-shaped valleys unlike streams that have V-shaped valleys

21 D. Glacial Erosion 1. Glaciers behave like huge bulldozers a) they push along anything loose that is in front of, underneath or beside the glacier

22 2. Plucking a) boulders, gravel, & sand are broken loose by ice wedging. b) this loose material is then dragged along by a glacier

23 3. Striations a) long, deep, parallel grooves in the rock underneath the glacier b) are caused by boulders, sand, & gravel being dragged underneath the glacier

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25 a) valley glaciers erode a bowl shaped basin in the sides of Mountains
E. Evidence of Valley Glaciers 1. Cirque a) valley glaciers erode a bowl shaped basin in the sides of Mountains 2. Arête a) 2 or more glaciers have eroded a mountain summit to form a sharpened peak b) these sharpened peaks are called horns c) Ex. Materhorn, Swiss Alps

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27 3. U-shaped Valleys a) as a valley glacier moves along it carves the valley out into a U- shape 4. Kettle Lakes a) lakes formed when huge blocks of ice melt

28 F. Glacial Deposition 1. Till a) a mixture of different sized sediments b) includes silt, clay, sand, and boulders

29 2. Moraine a) a large pile of material that is piled up and left by a moving glacier b) terminal moraine: a ridge of material at the end of a glacier c) lateral moraine: a ridge of material at the sides of a glacier d) medial moraine: a ridge of material in the middle of glaciers

30 3. Outwash a) material deposited by melt water of a glacier b) heavier sediments are deposited closer to a glacier while smaller ones move farther away. c) esker: a winding ridge of sand & gravel deposited in tunnels beneath a glacier d) outwash plain: flat areas of deposited materials in front of a retreating (melting) glacier

31 4. Erratics a) large rock fragments deposited by a glacier b) some erratics have been transported hundreds of miles from its source

32 IV. Wind Erosion A. Deflation 1. Wind blows across loose sediments such as clay, silt, & sand and picks them up 2. After these sediments are removed only the larger, coarser ones remain 3. The coarse material left behind is called desert pavement

33 B. Abrasion 1. wind picks up loose silt, clay, & sand sized sediments 2. the sediments are blown into rocks or buildings 3. the force of these sediments breaks down and erodes the rock (sandblasting) 4. ventifacts: rocks shaped by wind erosion

34 C. Sandstorms 1. strong winds blow sand off the ground 2. as the sand grains blow along they collide with other sand grains causing them to rise off the ground 3. Most sandstorms occur in the desert

35 D. Dust Storms 1. When a drought occurs the wind can easily pick up soil 2. Most soil particles are smaller than sand and are easily picked up 3. Dust Storms can cause these particles to be carried great distances a) 1930’s soil from Kansas was carried to Maine

36 E. Reducing Wind Erosion
1. Windbreaks a) farmers plant trees to stop the wind b) the trees and their roots help to hold the soil in place

37 2. Roots a) farmers plant cover crops to hold the soil down b) the deeper the root system the better it holds down soil c) planting vegetation is a good way to reduce the affects of deflation & abrasion

38 F. Deposition by Wind 1. Loess a) fine grained wind deposits b) the location loess is deposited forms fertile farmlands c) loess deposits in the USA were formed mainly from glacial outwash plains.

39 2. Dunes a) a mound of sand drifted by wind b) formed in places where there is sand and the wind blows daily c) can grow 50 to 180 meters high d) forms in areas of beaches, barrier islands, & deserts

40 3. Dune Migration a) sand dunes move with the wind b) windward side – side facing the wind c) leeward side- side facing away from the wind d) dunes move from the windward side towards the leeward side

41 Use your notes to answer the following:
1. Name 2 types of glaciers. 2. List the three types of moraines. 3. What is a ventifact? 4. What is loess? 5. How do dunes move?

42 1 ____ are bowl-shaped basins resulting from glacial erosion on the side of a mountain. a. Moraines c. Cirques b. Horns d. Striations

43 2 Many farmlands of the midwestern United States are on fertile soil that developed from ____. a. loess deposits c. cirques b. sand d. moraines

44 3 ____ can be compared to sandblasting. a. Deflation c. Plucking
b. Abrasion d. Deposition

45 4 Agents of ____ deposit sediments when they lose their energy of motion. a. deflation c. erosion b. abrasion d. plucking

46 5 When people plant vegetation, they ____ erosion. a. reduce c. start
b. increase d. do not affect

47 6 Trees, walls, and fence posts leaning downhill are signs of ____.
a. rockfalls c. creep b. mud flow d. slump

48 7 Boulders, gravel, and sand are added to the bottom of the glacier by ____. a. gravity c. plucking b. rivers d. abrasion

49 8 Rock fragments dragged by glaciers will gouge ____ into the rock over which they are moving. a. arêtes b. cirques c. grooves and striations d. moraines

50 9 Striations are formed by large boulders carried by moving masses of ice and snow called ____. a. grooves c. glaciers b. cirques d. creep

51 10 Erosion caused by the sandblasting effect of windblown sediments is called ____. a. deflation c. loess b. abrasion d. outwash

52 11 A long, winding ridge called a(n) ____ is a type of outwash deposit. a. esker c. cirque b. striation d. moraine

53 12 A ridge consisting of mixed debris deposited by a glacier is a(n) ____. a. outwash plain c. moraine b. kettle d. esker

54 13 Which of the following is NOT an indication that creep has occurred? a. Parallel grooves form in bedrock. b. Trees become bent. c. Vertical structures become tilted d. Underground pipelines break.

55 14 Slumps are common after a rainfall because the water ____.
a. reduces friction between soil grains b. causes snow to melt c. breaks the underlying rock d. washes away the vegetation cover

56 15 Which of the following causes deflation? a. glacial erosion
b. wind deposition c. deposition by meltwaters d. wind erosion

57 16 Glaciers covered 30 percent of the earth during the last ice age that began about ____. a years ago b years ago c. 1.6 million years ago d. 50 million years ago

58 17 Which of the following is NOT true about glaciers?
a. Glaciers can form along the equator. b. Only valley glaciers flow. c. Glaciers carve U-shaped valleys. d. Glaciers produce moraines.

59 18 When two cirques on opposite sides of a valley meet, they form a(n) ____. a. arête c. moraine b. drumlin d. avalanche

60 19 A landslide that occurs on steep slopes in mountainous area is called a(n) ____. a. rockslide c. avalanche b. slump d. mudflow

61 20 True or False A landslide in which layers of snow slide down a mountainside at speeds of up to 300km/hr is a(n) rockslide. _________________________

62 21 True or False Because a heavy saturation of water greatly increases the weight of soils, the force of friction is more likely to pull the material downhill. _________________________

63 22 True or False The best way to reduce the number of disasters related to mass movements is to relocate people. _________________________

64 23 True or False The structure shown in the illustration below is shaped by wind-blown sediments and is called a(n) ventifact. _________________________

65 24 True or False Many parts of Earth’s surface are covered by thick layers of windblown silt that are called loess. _________________________

66 25 True or False When glaciers with embedded rocks move over bedrock valley walls, they grind out perpendicular grooves and scratches. _________________________


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