Water Erosion and Deposition

Water Erosion and Deposition

Chapter 9

Shorelines

When waves constantly pound against the shore, they break rocks into ever-smaller pieces.

Shorelines

There are three factors that affect shorelines: 1. waves; 2. currents; 3. tides.

Waves usually always hit a shoreline at an angle, this causes a longshore current. This current runs parallel to the shoreline. These currents carry a large amount of sediment.

Sandy Beaches

Rocky Shorelines

A rocky beach is one covered in rocks and sea cliffs. Waves crash against the rocks and the cliffs and erode them. Softer rocks erode faster than harder rocks.

Has anyone ever heard of strawberry rock?

Smooth, gently sloping shorlines create beaches. Beaches are deposits of sediment that are parallel to the shore.

Beaches can be made of:

• rocks
• quartz
• seashells

Constant wave action always breaks these materials into sand sized particles. This is why sand looks different for each beach you are on.

Underground Water

Surface Water

Groundwater

Well: a well extends deep into the zone of saturation and water gets pumped to the surface. Even good wells can run dry.

Springs: in some places, the water table is so close to Earth's surface that water flows out and forms a spring. Usually found on hillsides, the water table intersects the surface.

When water soaks into the ground and collects in pores, and empty spaces it becomes groundwater.

Geysers: is a hot spring that erupts periodically, shooting water and steam into the air. This happens because underground water gets super heated, and evaporates. This causes pressure to build.

Surface water is obviously, water that stays on the surface of Earth. More specifically: runoff is any water that doesn't soak into the ground, or evaporate but instead flows across Earth's surface.

Some soils and rocks are permeable, which means that they have pores and empty spaces for water to flow through or accumulate. If there are no pore spaces or places for water to flow into, it's called impermeable.

Homework!

Groundwater will keep moving until it reaches a layer of impermeable rock. This prevents water from moving down, and instead it starts to accumulate. We call this underground water storage an aquifer.

Types of runoff to know:

Rill and Gully Erosion: Rill erosion begins when a small stream forms during a heavy rain. This small stream carries away soil creating a channel.

• When these channels become larger, and frequently have water running down them, we refer to this as Gully Erosion.

The upper surface of an aquifer or water storage area is referred to as the water table.

Read Chapter 9. Complete:

• Pg. 248: 1-4
• Pg. 251: 1-2
• Pg. 254: 1-3
• Pgs. 264-265: 1-21.

Due: 11/18.

Sheet Erosion: occurs when water that is flowing as sheets picks up and carries away sediments.

Water Erosion and Deposition

Stream erosion: water in streams will pick up and carry sediment from the bottom and sides of the stream and carry them along. The sediment that a stream carries is referred to as it's load.

• A stream's load can be suspended (which means that it is mixed in with the stream water or it could just roll along the bottom of the stream.

Water has the ability to cause significant erosion to all of Earth's surfaces. We are going to look at:

1. Surface water

2. Groundwater

3. Shorelines.

TOO MUCH WATER!

River systems only carry so much water in them. But, that doesn't mean that certain events can cause rivers to go beyond the normal amount of water they carry. We call this flooding.

Flooding can be extremely damaging, and can cause severe erosion. Flooding can be small or it can be extremely large.

River Systems

Streams are parts of river systems. Runoff enters small streams, which join together to form larger streams. Larger streams come together to form rivers and rivers grow and carry more water as more streams join.

A drainage basin is the area of land from which a stream or river collects runoff. Think of a bathtub. All the water that lands in a bathtub will all still flow toward one location: the drain.

Stages of Stream Development

Young streams: a stream that flows swiftly through a steep valley. Water flowing through a steep channel with a rough bottom has a high level of energy.

Mature Streams: This stream flows more smoothly through its valley. Erosion is no longer concentrated on the bottom of the stream, but instead at it's sides. This causes currents to flow at different rates. Where the current flows can cause "curves" to form in the stream. Over time these curves become broad, large arcs called meanders.

Old Streams: an old stream flows smoothly through a broad, flat floodplain that it has deposited.

Sediment and Surface Water

Water that flows quickly has a lot of energy, and will carry a lot of sediment. As the slope becomes more shallow, water slows down and will deposit a lot of its load.

A delta or an alluvial fan is when sediment makes a triangle shape when and where it's deposited.