Unit 1 Lesson 3 - Erosion and Deposition by Water

Coastal landforms - beach - deposition

A beach is an area on the shoreline where the waves and currents deposit materials including sane, rock, dead coral and shells

Deposition

After streams erode rock and soil, they eventually drop or deposit it downstream. Deposition is the process by which eroded material is dropped. Deposition occurs when gravity's downward pull is stronger than the streams push.

Stalactities

Are formed by deposition in caves.

Caves

Are formed when slightly acidic underground water dissolves rock and moves around. Caves are formed by erosion. When the groundwater level is lower than the level of the cave, the cave roof may no longer be supported by the water and can collapse (sink hole)

Landforms that streams can create by Erosion

Canyons and Valleys

Meanders

Curves and bends in the river

Oxbow lake

Cut off meander - a crescent-shaped lake.

How does flowing water change the earth's surface?

Erosion and Deposition

Landforms that streams can create by Deposition

Floodplains and Deltas and Alluvial Plains

Canyons and Valleys by water erosion

Flowing water can cause canyons and valleys to form. For example, the Colorado River cut down into the rock and formed the Grand Canyon over millions of years.

What factors affect a streams ability to erode material?

Gradient, Load, Discharge

Coastal landform - Barrier Island - Deposition

Is a long narrow island usually made of sand that forms parallel to the shoreline

Channel

Is the path that a stream follows. A stream is really where water erodes the soil and rock and forms the channel. Over time it gets wider and deeper and it can lead to canyons and valleys forming

Shoreline

Is the place where land and a body of water meet

Sinkhole

Is when the roof of a cave collapses

Load of a river

Materials carried in a stream is called the load. The size of the particles in the load can affect the erosion. Big particles and fast flow means more erosion or erosive energy

Erosion

Rivers and streams erode soil, rock and sediment as they flow. Process by which sediment and other materials are moved from one place to another

Coastal landforms made by erosion - Sea caves, arches and stacks

Sea caves form when waves cut into the base of cliffs; Sea arches form when wave action erodes the sea caves until it forms a hole; sea stack is when the top of the sea arch collapses and leaves behind isolated columns of rock

Alluvial Fan

Similar to the Delta but not the same. This is when the stream flows onto a flat land surface from mountains or hills. On land this forms a fan shape.

Discharge

The amount of water a stream carries in a given amount of time is called Discharge. The discharge increases with the amount of water - eg after a storm or after ice melts. As the streams discharge increases, its erosive energy, speed and load increase.

Gradient of a river

The measure of change in the elevation over a certain distance. The steeper the gradient the quicker the stream flows. The quicker the river the greater the erosion power.

How are shorelines formed?

Waves and currents

Waves

Waves build up and breakdown a shoreline. Waves slow down as they meet the shoreline. The first part the waves meet is the Headland which takes most of the energy from the waves. The waves striking areas between headlands have less energy and are more likely to deposit materials

Deltas

When a stream empties into a lake or the ocean, its current slows and it deposits its load - often in a fan-shaped pattern called a delta. Sometimes it can keep building up so it forms land

Floodplains by deposition

When a stream floods, a layer of sediment is deposited over the flooded land. This is called the flat floodplain and is excellent for agriculture

Longshore Currents

When water travels almost parallel to the shoreline near the shore, the current is called a longshore current when the waves hit the shorline at an angle and cause zig zag sand patterns to form

Coastal landforms made by erosion - Sea Cliffs and wave cut platforms

When waves erode and undercut rock to make steep slopes. Wave cut platforms form when a sea cliff is worn back from shore producing a nearly level platform beneath the water at the base of the cliff

Coastal landforms - Sandbars - deposition

When waves erode material from the shoreline longshore currents can transport and deposit the materials off-shore to create a landform in open water