Erosion Weathered rock particles are transported Agents of erosion The actual process doing the eroding Gravity Running water Wind Glaciers Waves Human activity Gravity is the driving force behind most erosion

Erosion by Gravity Mass Movement Gravity pulls rock sediments downhill Soil creep Debris flow Rock fall

Running Water Most common agent of erosion on Earth Stream Tributary A flowing body of water confined to a channel Tributary A smaller stream that feeds into a larger one

Stream Valleys Streams carve out V-shaped valleys Watershed The drainage area of a stream

Watersheds

Continental Divide Argentina

Stream Velocity Determined by 3 factors: Gradient Discharge (Volume) steeper= = faster Discharge (Volume) more discharge = faster Shape of the channel less contact with sides = faster

Velocity within a Stream Velocity is not the same throughout the stream

Where is the fastest part? Straight Stream Fastest Part??? In a straight stream, the fastest part is in the middle slightly below the surface

Where is the fastest part? Curved Stream Fastest Part??? In a curved stream, the fastest part is on the outside of the curve and slightly below the surface

Importance of Stream Velocity The faster a stream moves the larger sized particles it can carry

How a Stream Carries Sediment Sediments can be carried in different ways: Bouncing & Rolling Suspension Solution

Stream Stages Youthful Mature Old Age

Stream Evolution Youthful Straight channel Narrow valley Steep gradient Rapids & waterfalls

Stream Evolution Mature Stream Not as straight Gradient not as steep Little or no waterfalls & rapids

Stream Evolution Old Age Stream Features: Gradient & Velocity very low Meanders Oxbow Lakes Floodplains

Meanders meanders

Oxbow Lakes

Floodplains

Mature Stream

Mississippi River

River Delta Where a stream enters a large body of water