1. Weathering, Erosion, and Soil
What type of rock is this, how can you tell?

2. Yosemite Valley, California
Mountains Carved by Glaciers

3. Grand Canyon, Arizona
Carved out by the Colorado River

4. Bryce Canyon, Utah Acidic Rainfall has worn away these rocks.
The harder rocks remain standing… but for how long?

5. Weathering The 2 G’s and the 3 W’s
Process by which rocks are broken down due to exposure to processes occurring at the Earth’s surface
Caused by
Water
Waves
Wind
Gravity
Glaciers
The 2 G’s and the 3 W’s

6. 2 Types of Weathering
A. Mechanical Weathering also called Physical weathering
Rock is broken down into smaller pieces of the same material
(no change in composition)
B. Chemical Weathering
The breakdown or decomposition of rock that occurs when minerals are changed into different substances
(change in composition)

7. Mechanical/Physical Weathering
Frost (Ice) Wedging
Process in which water freezes in the cracks of rock and wedges (pushes) it apart because water expands when it freezes.
Occurs where there are frequent freezes and thaws.

8. Explain what is happening.

9. Frost/Ice Wedging can cause Potholes to form in pavement

10. Mechanical/Physical Weathering
2. Abrasion
The wearing away of rock material by grinding action
Usually caused by sediment in Wind, Water, and Glaciers

11. Wind abrasion- sandblasting effect on stationary rocks as seen here in Arches National Park

12. Hydraulic abrasion- water & sediments flowing over boulders as seen here in Ohiopyle State Park, Pennsylvania
Notice the rounded river rocks

13. Mechanical/Physical Weathering
3. Plants and Animals
Plant roots can split rock
Also known as: “Root pry” or “Root action”
Animals dig holes ,breaks up rocks

14. Tree growing
out of rock,
Shenandoah
National Park
Tree roots also break up sidewalks

15. Mechanical/Physical Weathering
Exfoliation- gradual peeling of layers due to uplift and frost action, typical of granite domes like those in Yosemite N.P.

16. Exfoliation of Igneous rock

17. O2 Chemical Weathering Chemical Weathering
The breakdown or decomposition of rock that occurs when minerals are changed into different substances
(change in composition)
Involves Water ,water vapor, Acids, and/or Oxygen O2

18. Chemical Weathering Hydrolysis
Carbonic Acid in water dissolves Calcite. This chemical weathering can hollow out underground Caverns
Limestone and Dolomite both dissolve because they contain Calcite

19. Acid rain (carbonic acid) weathering the details of statues and tombstones Ex: Marble and Limestone

20. Chemical Weathering Oxidation This is why Mars is the red planet
Oxidation of minerals with iron (magnetite, pyrite) results in the formation of rust or iron oxide.
This is why Mars is the red planet
Copper turns rocks green

21. Rate of Weathering Surface area Rock composition Climate
How fast a rock weathers depends on 3 factors:
Surface area
Rock composition
Climate

22. Rate of Weathering Surface area
The greater the surface area, the faster the weathering rate
There are more surfaces to be weathered

23. Rate of Weathering Rock composition
Some minerals are more resistant than others
For example, quartz is more resistant (harder) than calcite
Quartz
Calcite

24. Rate of Weathering Climate
(long term pattern of moisture and temperature)
Weathering rates are faster in warm, wet climates
Desert vs. Rainforest

25. Erosion
Erosion
The removal and transport of weathered materials by natural agents such as
Caused by
Glaciers
Running water
Gravity
Wind
Waves

26. Glaciers
Mass of compacted ice and snow that moves under its own weight

27. Glaciers
Friction at the base of the glacier is reduced by a thin film of melt water.
Glaciers account for about 75% of the fresh water on Earth

28. Glaciers can leave behind large boulders that are known as an erratic

29. Glaciers
Glaciers can move lots of sediment that can carve striations (grooves) into rocks
These Striations show how glaciers moved

30. Glacial Deposits
Drift or Till - all sediment that is deposited by glacial activity
Loess: fine powder, pulverized rock, that blankets much of the northern mid-west
Moraine: ridge or pile of boulders, gravel, sand, and silt left at the end of a glacier
Esker: type of outwash that accumulates in the channels and tunnels of a glacier

31. Glacial Landforms
Horne: a pyramid shaped peak where 3 or more cirques meet
Cirque
Steep-walled bowl-shaped depression

32. Glacial Landforms Trough
U-shaped valley, Glaciers carve U shaped valleys

33. Glacial Landforms Arete Hanging valley
Narrow flat-topped ridge that forms between two parallel troughs or cirques
Hanging valley
Straight drop-off at the end of a trough

34. Glacial Landforms
Moraine: Pile of mixed sediments that have been carried and dropped by the glacier

35. Glacial Landforms
Eskers -Mounds of rock from melt tunnels

37. Streams and Rivers Velocity - How fast the water moves
Gradient - The steepness, the slope that a river or stream travels
Discharge - The amount of water that moves past a certain point in a river in a given amount of time
If there is a steep gradient, high velocity, and a large discharge, then Erosion will be severe!
Rivers have energy to move lots of sediment, and even large boulders.

38. River stages affect: Velocity, Gradient, & discharge which cause Erosion

40. Seven Bends of the Shenandoah
River meanders
Bends in the river, shows how mature a river is.
Is the Shenandoah and old river or a young river?

41. Erosion-Mass Movement
The downward transportation of weathered materials by gravity
Massive Landslide

42. Erosion-Mass Movement
Creep
Slump
Mudflow/Earthflow
Landslide/Rockslide

43. Erosion-Mass Movement: A large mass of sediment drops down!

44. Erosion-Mass Movement
Creep
Very slow movement of earth material.
Caused by repeated freezing and thawing.
Sediments are loosened by expanding frost and contracting thaw.
Leaning fence posts and telephone poles are a sign of Creep.

45. Fence posts leaning due to creep

46. Erosion-Mass Movement
Slump
Slow downward movement of a large mass of soil
Occurs when underlying sediments are weakened by heavy rains
Characterized by a curved scar in the land surface.

47. Slump can cause road hazards

48. Erosion-Mass Movement
Mudflow/Earthflow
Thick pastes of sediments that travel downhill at great speeds
Usually occur in dry areas that get a large quantity of rain all at once
Leaves a cone shaped deposit

49. Mudflow in the Blue Ridge Mooreman’s Gap near Charlottesville

50. Erosion-Mass Movement
Landslide/Rockslide
Fast movement of large blocks of rock
Occurs in very steep vertical cliffs
Accelerated by ice wedging

51. At the bottom of an old rock slide in N.C. 2011

52. Wave Erosion
The crashing of waves on a shoreline combined with storms continually shape the beach. This is a shoreline with erosion.

54. Wind and Waves
Wind moves sand dunes at the beach and in the deserts.

55. Wind and Waves
Wind can carve out landscapes as it carries sediment

56. Wind and Waves
Many storms combine water and wind to cause significant erosion on landforms.
Strong winds are capable of moving large amounts of sediment

57. Deposition: The process of dropping or depositing soil and sediments.

58. Soil (dirt)
Soil includes loose weathered rock, and organic material in which plant roots can grow

59. Soil Composition
Use this pie chart to answer the questions in your notes.

60. Soil Composition
What do the arrows mean?

61. Where soil forms Residual soil Transported soil
The parent rock is the bedrock beneath the soil (the soil has not moved)
Transported soil
Soil forms from parent material left by winds, rivers, glaciers, or soil that was moved from its original location. This soil has been transported by erosion and deposition

62. Factors that affect Soil Composition
Parent material: What bedrock is it from?
Time: How long has it had to decompose?
Plants and animals: How have roots and animals helped break up the rocks? Were there acid producing mosses that help break down the rocks (chemical weathering)?
Topography: What is the shape of the landscape?
Climate: Is it warm & wet? Were there glaciers present? Was there acid rain?

63. Soil Profile
Cross section of soil layers revealing all soil horizons

64. Soil Horizon
A soil layer with physical and chemical properties that are different from adjacent layers
O Horizon= organic material (humus)
A Horizon = topsoil
B Horizon = subsoil
C Horizon = partially weathered parent material

65. Idealized Soil Profile
Humus:
Dark organic matter in soil that is rich in nutrients.

66. Leaching: The removal of nutrients or toxins in soil as water passes through the layers.

67. Soil Texture
The size of soil particles

68. Particle size ranges for sand, silt and clay
 Type of Mineral Particle
  Size Range
 Sand
  millimeters
 Silt
  millimeters
 Clay
 less than millimeters
Large/ Coarse
Medium
Small/ Fine

69. erosion
EROSION

70. Weathering

71. Deposition

72. Sedimentation
to “settle”