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AIM: What forces cause erosion?

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Presentation on theme: "AIM: What forces cause erosion?"— Presentation transcript:

1 AIM: What forces cause erosion?
Agents of Erosion AIM: What forces cause erosion?

2 Vocabulary Erosion Mass movement Landslide Creep Slump Mudslide
Avalanche Liquefaction Retaining Walls Slope

3 1. Erosion Movement of sediments from one location to another.
Landforms are created by a combination of weathering and erosion. Often the forces that cause erosion also cause the weathering of the sediment at the same time.

4 2. Gravity a. ***Driving force of all erosion ****
b.    Causes Mass Movement or Mass Wasting (Ex - Landslides, mudslides, slump and creep) c.    Affected by slope, ground cover, water, climate Can be triggered by earthquakes d. Sediments are angular and rough

5 a. Landslides or rockslides – fast moving



8 Retaining walls and metal nets help prevent landslides

9 b. Mudslides Downward flow of water, rock and soil
After heavy rain when ground is overly saturated, where vegetation has been stripped, and on steep slopes Volcanoes can trigger a melt Liquefaction – when the land becomes fluid and moves

10 c. Slump – a sudden sag or dip

11 d. Creep – very slow movement downhill
Slanted fences, walls, trees or gravestones are a sign of creep.

12 e. Avalanche- involves snow and ice

13 2. Wind a. Erodes fine, small, loose, dry material
b. Contributes to abrasion (physical weathering) c. Affected by velocity, sediment size, ground cover, water d. Sediments are angular with frosted or pitted appearance e. Occurs in deserts, arid areas, seashores

14 Wind erosion forms sand dunes.

15 How sand dunes form

16 Wind makes odd shapes and angular rocks

17 Wind also makes swirly patterns

18 The Great Dust Bowl – the Dirty 30s Wind can erode away topsoil

19 Vegetation reduces erosion of dunes

20 Draw a sand dune with the sand blowing from the right.

21 How does gravity play a role in wind erosion?
Gravity causes wind to drop it’s sediments in a new location.

22 What kind of weathering does wind cause while it’s eroding sediments?
Wind carries sand and fine particles which can abrade rock (abrasion by wind).

23 Weatherhing and erosion games

24 1) The photograph shows a sand dune that formed in a coastal area
1) The photograph shows a sand dune that formed in a coastal area.                                                  This sand dune was most likely formed by A) water flowing from the left B) water flowing from the right C) wind blowing from the left D) wind blowing from the right

25 The picture below shows a geological feature in the Kalahari Desert of southwestern Africa.                                                                        Which process most likely produced the present appearance of this feature? A) wind erosion B) volcanic eruption C) earthquake vibrations D) plate tectonics

26 3. Glacial Landmasses Glacier – a large mass of moving ice, found in areas of - High elevation ( mountaintops) - High latitude ( polar regions) b. Two types: Valley glacier – long and narrow, forms high in the mountains Continental glacier – ice caps, covers much land, ex – Greenland, Antarctica, Alaska

27 3. Glaciers c. Gravity pulls weight of glacier down mountain
d. Glaciers can move cm/day e. Affected by slope, weight, and velocity f. Erodes many sizes - boulders to sand g. Sediments are unsorted (mixed sizes) h. Sediments have sharp angles, irregular shapes,rough, grooves (striations) i. Carve U-shaped valleys

28 Ice ages – when glaciers covered large parts of the Earth’s surface

29 Glaciers – carve a U-shaped valley



32 As the glacier moves it drags sediment downhill.

33 Other glacial landforms

34 Glacial erosion Plucking – rocks freeze to the glacier and moves it
Abrasion – rocks in glacier scratch bedrock causing striations

35 Striations – grooves carved in rock can tell you the way a glacier moved

36 Glacial Deposition When sediments are eroded, they must come to rest somewhere. They are deposited in a location that creates a landform. Glaciers deposit sediments, as well as water, wind and gravity.

37 Glacial Deposition Till – the sediment piles that are created by glaciers are unsorted deposits, meaning they have many shapes and sizes of sediments.

38 Glacial Deposition Moraine – till deposited at the edge of a glacier makes a mound

39 How moraines are formed

40 Glacial Deposition Drumlin-elongated whale-shaped hill formed by glacial ice. They point the direction of glacial retreat.

41 Glacial Deposition Glacial Erratic – a boulder dragged by a glacier to a new location, from a different origin

42 Glacial Deposition A kettle lake is a hole left by a chunk of ice and filled by melting glacial water and runoff.

43 Glacial Deposition Glacial Outwash- sediments washed away from the glaciers front end. These sediment are deposited, sorted by size in layers.

44 Glacial Deposition Eskers – a long winding ridge formed when a river of melting ice forms inside the glacier

45 Glacial Outwash

46 Glacier Game

47 4. Wave Action a. Wave action brings in (deposits) and carries away (erodes) sand along coastlines. b. Wind creates waves. b. Affected by tides. c. Sediments are rounded from abrasion.

48 Waves shaping the coast

49 5. Stream erosion (Running Water)
a.    ****Primary agent of erosion **** b.    Size of sediment carried depends on velocity of water c.    Sediments are rounded from abrasion d. Carve V-shaped valleys

50 Stream carved V-shaped valley

51 Figure A steep mountain stream eroded a V-shaped valley into soft shale in the Canadian Rockies.

52 Streams weather and erode waterfalls – softer rock erodes, while harder rock remains

53 Waterfall formation waterfall formation

54 Broken boulders at the bottom of the falls

55 Question… Which agents of erosion also weather rocks at the same time?

56 Question… How is gravity involved in stream erosion?

57 Now it’s your turn… Look at the following pictures
Identify the type of erosion Match the cut-out sediment type transported in each example.





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