1. Ch. 23.3 Water Shapes the Land
Objectives:
What is the most important factor influencing the ability of a stream to cause erosion?
What features are formed by surface water erosion?
What features are deposited by running water?
What causes ground water erosion?

2. Stream A Stream B Define erosion in your notebooks.
Which stream will cause more erosion? Provide 2 reasons why you chose one stream over the other.
Stream A
Stream B

3. Water moves sediment (Erosion) & that changes Earth’s surface features
Deposition = Sediment is laid down in a new location

4. Stream Erosion – Depends on…
Speed of water: Faster streams – carry more sediment & carry larger sediments = more erosion
(2) Volume: Floods = More water = more erosion
(3) Slope: Steeper slope = more erosion.

5. Features formed by Water Erosion: V shaped Valleys
V-valleys involve fast moving water in Mt. regions
Fast Moving Water Carries away sediments and causes downward erosion

6. V-shaped valleys can widen into broader river banks and flood plains.
Water slows and erodes the sides of the stream

7.
Waterfalls form where streams move over rocks that are (softer). As this rock erodes faster than surrounding rock a drop is created.

8. Meanders:
Rivers change shape. Faster moving water on outside bend erodes riverbank.
Slower moving water on inside bends deposit sediment.
Over time this creates BENDS or MEANDERS.

10. Meander in Canyonlands N.P., Utah

11. Features formed by Water Erosion
Oxbow lake: a U-shaped lake lying next to a winding river

12. Green River, NY

13. Features Formed by Water Deposition
Deltas & Alluvial Fans: Fan-shaped mound of sediments.
Fans: Rivers dump sediment into a valley at the base of a mountain.
Deltas: Rivers dump sediments into large bodies of water (ocean).
Triangle shape of Deltas & Fans

14. Copper Canyon Alluvial Fan
(Death Valley N.P., CA)

15. Mississippi River Delta

17. Ground Water Erosion
Chemical weathering dissolves calcium containing rocks like limestone. This creates caves and sink holes.
Sink hole
Carlsbad Caverns

18. Cave Formation: Chemical Weathering (usu. Limestone)
- Water drips into cave. Carbon dioxide enters air, minerals come out of solution to form stalactites & Stalagmites
Stalactites: Grow from ceiling (icicles)
Stalagmites: Grow from base & form columns

19. Carlsbad Caverns (NM)
Limestone slowly dissolving away

21. Karst Topography (caves and sinkholes in limestone) Ex: Kentucky

22. Ch. 23.4 Glaciers & Wind Objectives: How do glaciers form?
What landscape features are created by glacial erosion & deposition?
What are the effects of wind erosion & deposition

23. HW QUIZ Describe 2 features/landforms created by glacial erosion.
What’s “Moraine” and how is it created?
How are dunes created?

24. Glaciers – Where more snow falls than melts or evaporates
Types:
Continental: Thick ice sheet on huge land mass (Antarctica or Greenland)
(icebergs “calve” off continental marine glaciers)
Valley: Occurs in high mountain valley

25. Characteristics of Glaciers
Large body of ice that forms Where more snow falls than melts or evaporates
Glaciers are always slowly moving
- Weight of snow pressing down, makes ice.
- Gravity pulls the glaciers down hill
- Weight of ice layers also melts bottom layer of ice so that glacier can slide.

26. Glacial Erosion
1. Plucking – frost wedging that occurs at the base of the glacier breaks up rock.
2. Abrasion – boulders trapped under glaciers gouge and scratch our land and rock surfaces (Glacial striations = claw marks)

27. Glacial Erosion produces…
1. U shaped Valley (Cirques)
2. Horns
3. Glacial Lakes

28. Glacial Signatures… 4. “Erratic” Boulder =
deposited by receding glacier
5. Till = Glacial sediment of assorted size (Boulders, gravel, sand, pulverized rock dust) formed as glacier erodes surface
6. Moraine – mounds of “poorly sorted” sediment at downhill end of glacier and along sides (Poorly sorted = big clasts/cobbles & fine sediment)

31. Central Park, NYC
Striations in rock show the motion of ancient ice sheets.

32. Poorly Sorted Glacial Till

33. Glacier Features

34. Glaciation in our Area

35. Wind Erosion & Deposition
Wind erodes land by deflation (wind picks up & carries loose surface material) and abrasion
Wind Deposits: Dunes & Loess
Loess – silt deposits from glaciers or deserts
Sand Dunes