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EROSION- The transport of weathered materials….

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Presentation on theme: "EROSION- The transport of weathered materials…."— Presentation transcript:

1 EROSION- The transport of weathered materials…

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3 Major Erosive Agents: Running Water GLACIERS WIND OCEAN CURRENTS AND WAVES MASS WASTING (GRAVITY!)

4 What happens to rainfall when it hits earth???? Some evaporates Some is absorbed and becomes ground water Some is run off

5 What determines if rainwater becomes runoff or groundwater? Ground Conditions : Saturated vs. unsaturated Vegetation – amount of plants Slope or Gradient of the Land

6 Running Water – Most of North America is above sea level. Water flows high to low sea level due to gravity

7 When Runoff becomes confined to a channel – Stream Exists

8 Watersheds or Drainage Basins Smaller stream that flows into a larger stream is called a tributary Tributaries and land that contribute to the stream is called a drainage basin or watershed (COMPARED TO A BATHTUB. WATER THAT COLLECTS IN A BATHTUB FLOWS TOWARD THE DRAIN.) The drainage basin of one stream is separated by a drainage divide (ridges or mountains – higher elevations)

9 HOW WATERSHEDS/DRAINAGE BASINS FORM – RED LINE IS DRAINAGE DIVIDE

10 Watersheds: Continental Divide and Appalachian Mountains Water goes from high sea level to low sea level

11 Watershed Regions of New York State

12 EROSION- The transport of weathered materials…

13 STREAMS (the most important source of moving water…) ALL streams flow * fill in the blank * Streams begin at the HEAD and end at the MOUTH. Streamflow is contained within a CHANNEL or STREAM BED

14 STREAMS CARRY MATERIAL IN … Solution: dissolved material (includes salts) Suspension: particles carried in the flow of the water (Clay, silt, sand) Bed load: particles carried by rolling, bouncing, or dragging along the stream bed (Pebbles, cobbles, boulders)

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16 3 factors affecting Stream Velocity  Gradient – slope of the stream  Discharge – volume of water  Stream channel shape

17 Stream Velocity in a Straight Channel Fastest – middle just below surface

18 The velocity changes in the S-shaped curves called MEANDERS. Fastest on the outside of the curve – erosion Slowest on the inside of the curve - deposition

19 THE GREATER THE VELOCITY OF A STREAM…  THE LARGER THE SEDIMENT PARTICLES IT CAN CARRY  THE MORE TOTAL SEDIMENTS IT CAN CARRY

20 Water Velocity determines the size particle that can be moved via suspension and bed load

21 Do Now: Particle size worksheet

22 Stream Development – Early Stage The landscape is continuously being reshaped by stream erosion. Plateaus can be cut by rivers to form canyons. Valleys can be carved in mountains as rivers flow through them. As the stream begins to down cut into the land – waterfalls and rapids form

23 Stream Development – Young Stage V-Shaped Valley Rapids and Waterfalls No Flood Plain – a level plain that borders stream

24 V-SHAPED VALLEY…

25 RAPIDS AND WATERFALLS Rapids - Different resistance among rocks cause FAST-FLOWING WATER Waterfalls – Rapids develop into waterfalls as softer rock erodes

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28 Stream Development - Mature Stage Lateral erosion widens the valley profile – slope decreases River meanders pronounced A FLOOD PLAIN develops

29 As the stream grows larger – it begins to shift its course in a series of bends or curves called meanders seeking out the lowest elevation

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32 Point Bars show deposition Cut Banks show erosion

33 Cut bank on outside of curve due to higher velocity of water – more erosion Cut bank on outside of curve Point Bar on inside of curve

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36 Stream Development - Old Age Very Wide Flood Plain Land worn down to flat surface Oxbow Lakes

37 Stream Development – Old Age

38 Eventually, it takes too much energy to keep meandering, so rivers will cut off a bend, resulting in an OXBOW lake…

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43 What is the correct sequence in stream development?

44 SEDIMENTS ERODED BY RUNNING WATER WILL HAVE THESE CHARACTERISTICS ROUNDED and SMOOTH SORTED AND LAYERED

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46 SEDIMENTS ERODED BY RUNNING WATER WILL BE … SORTED – all materials are about the same size

47 Contour lines showing head of the stream to the mouth of stream with delta Velocity slows when entering a large body of water

48 Alluvial fans form when streams come out of mountains onto flat land – velocity slows and deposition occurs

49 Erosion by Waves and Long shore Current Where lake or ocean waters meet land, waves and currents act as agents of erosion, creating unique landscape features

50 Winds at the ocean’s surface cause waves

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52 Longshore Current Waves are refracted or bent in the shallow water of the shore Water near the shore is pushed in one direction along the shore – called longshore current Sediments are carried in a zig-zag pattern in the SAME direction as the longshore current

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57 The sand trapping effect of the jetties to the north at Charleston, South Carolina has deprived Morris Island of needed sand. As a result, the island has eroded to the point that this previously land based lighthouse is now 400 meters out to sea.

58 Which direction is the long shore current carrying sediment????

59 Barrier Islands Wave Action creates sand bars Waves and Longshore current - can form barrier islands Ex. Fire Island

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61 Wind Erosion Sediment – sand or smaller Arid regions or ocean coastlines 2 types: 1. Deflation – lowers the land 2. Sandblasting and Abrasion

62 Sandblasting and Abrasion Wind can only lift sand to about 1 meter high - results in “Mushroom Rock” Frosted or Pitted sediments – rocks with flat sides

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65 Windward side Leeward side

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