Presentation on theme: "Ch Water Shapes the Land"— Presentation transcript:
1Ch. 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?
2Water moves sediment (Erosion) & that changes Earth’s surface features Deposition = Sediment is laid down in a new location
3Stream Erosion – Depends on… (1) 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.Features formed by water erosion:V shaped ValleysWaterfallsMeandersOxbow Lakes
4Features formed by Water Erosion: V shaped Valleys Streams flow fast down slopes & carry sediments from the stream bed with them – creating a V patternV-valleys involve fast moving water in Mt. regionsmeander
5Yellowstone River has cut a V-shaped valley Waterfalls form where streams move over rocks that are less resistant to weathering (softer). As this rock erodes faster than surrounding rock a drop is created.
6V-shaped valleys can widen into broader river banks and flood plains. Rivers change shape. Faster moving water on outside bend erodes riverbank (cutbank). Slower moving water on inside bends deposit sediment. Over time this creates BENDS or MEANDERS.
13Features 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
14Copper Canyon Alluvial Fan (Death Valley N.P., CA)
17Ground Water ErosionSink holeChemical weathering dissolves calcium containing rocks like limestone.Results:Caves/Caverns and Sink Holes formCarlsbad Caverns
18Cave Formation: Chemical Weathering (usu. Limestone) Stalactites: Grow from ceiling (icicles)Water drips into cave. Carbon dioxide enters air, minerals come out of solution to form stalactites & StalagmitesStalagmites: Grow from base & form columnsStalagtites: Grow from ceiling
21Karst Topography (caves and sinkholes in limestone) Ex: Kentucky
22Ch. 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
23HW QUIZ Describe 2 features/landforms created by glacial erosion. What’s “Moraine” and how is it created?How are dunes created?
24Glaciers – Where more snow falls than melts or sublimates Continental: Thick ice sheet on huge land mass (Antarctica or Greenland)Valley: Occurs in high mountain valley(icebergs “calve” off continental marine glaciers)
25Glaciers are move slowly Weight of snow pressing down, makes ice.Weight of ice layers also melts bottom layer of ice so that glacier can slide.
26Glacial Erosion1. Abrasion – boulders trapped under glaciers gouge and scratch our land and rock surfaces (Glacial striations = claw marks)2. Plucking – frost wedging that occurs at the base of the glacier breaks up rock.
27Glacial Erosion produces… 1. U shaped Valley (Cirques)2. Horns3. Glacial Lakes
28Glacial Signatures… 4. “Erratic” Boulder = deposited by receding glacier5. Till = Glacial sediment of assorted size (Boulders, gravel, sand, pulverized rock dust) formed as glacier erodes surface6. Moraine – mounds of “poorly sorted” sediment at downhill end of glacier and along sides (Poorly sorted = big clasts/cobbles & fine sediment)