3 Major Erosive Agents: Running Water GLACIERS WIND OCEAN CURRENTS AND WAVESMASS WASTING (GRAVITY!)
4 What happens to rainfall when it hits earth???? Some evaporatesSome is absorbed and becomes ground waterSome is run off
5 What determines if rainwater becomes runoff or groundwater? Ground Conditions:Saturated vs. unsaturatedVegetation – amount of plantsSlope or Gradient of the Land
6 Running Water – Most of North America is above sea level 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 tributaryTributaries 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
12 The transport of weathered materials… 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)
16 3 factors affecting Stream Velocity Gradient – slope of the streamDischarge – volume of waterStream 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 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 CARRYTHE MORE TOTAL SEDIMENTS IT CAN CARRY
20 Water Velocity determines the size particle that can be moved via suspension and bed load
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 ValleyRapids and WaterfallsNo Flood Plain – a level plain that borders stream
52 Longshore CurrentWaves are refracted or bent in the shallow water of the shoreWater near the shore is pushed in one direction along the shore – called longshore currentSediments are carried in a zig-zag pattern in the SAME direction as the longshore current
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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