L.O: swbat explain STREAM EROSION.

The lands are being “washed away”( eroded) by water! Think, Pair, Share: compare the two images. Write 3 things you notice. WHY do you think this event is happening? The lands are being “washed away”( eroded) by water!

Erosion: The carrying of weathered rock material by agents such as water, wind, glaciers, or gravity.

“things fall apart”! EROSION HAPPENS AFTER WEATHERING Weathering: when rocks fall apart into sediment (rock particles) EROSION HAPPENS AFTER WEATHERING “things fall apart”!

Waves washing away the sand of beach is erosion

Gravity Wind Waves Glaciers (Ice) Running water What are the agents of erosion? Gravity Wind Waves Glaciers (Ice) Running water

Today, we will learn about stream erosion (erosion by running water)!

Running Water Running water is the most common agent of erosion. Moving water causes the following: 1) Sediments are rounded by abrasion 2) The stream bed (where it flows) becomes wider and deeper due to abrasion. 3) Minerals can dissolve in the water.

Stream Bedload Bedload: sediment moved along the stream bed (bottom and sides of a stream). The ability of a stream to erode its bed depends on: 1) The speed of the water Called stream velocity 2) The volume of the water.

The faster the water is running the bigger the sediment and the more particles it can carry. River velocity is directly dependent on slope and volume of water (discharge). Large Particle Size Small slow fast Stream Velocity

Which stream will carry a larger bedload and larger sediments? Water Moving Slow (Low Velocity) Water Moving Fast (High Velocity) Stream A Stream B

In a straight stream, the highest stream velocity is the center of a stream.

Where would the highest stream velocity be? At points 1, 2, 3 or 4? the highest stream velocity is at point 3 because it is in the center. .

What do you notice about these streams (rivers)? They curve!

Meanders Meanders: curves and bends in a stream. The velocity is greater(faster) on the outer part of a meander. The velocity is lower (slower) on the inner part of a meander.

The position of a stream’s maximum velocity changes as the direction of its flow changes.

*in a meandering stream,The fastest stream velocity is always greatest on the outside of the curve .

*the fast moving water is “eating away” *because the outside is fastest, the greatest amount of erosion is on the outside of the curve. . *the fast moving water is “eating away” (eroding) the outside of meander.

*The slowest stream velocity is always on the inside of the curve, *deposition is greatest on the inside of the curve. .

*the stream is moving slowest on the inside of the meander (curve) so sediment is depositing there.

Some questions:

At which two points is the stream velocity fastest? Why?

At points B and D because they are on the outside of the stream’s meander (curve)

At which two points is the stream velocity slowest? Why?

At points C and E! because streams move slowest on the inside of the curve

Why is there more erosion at points B and D?

Why is there more deposition at points C and E?

These places have the highest velocity water because are the outsides of the curve (meander).

Also outside of the curve has the greatest erosion.