The Work of Rivers

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Slide 1

The Work of Rivers

The erosional work of streams/rivers carves and shapes the landscape through which they flow.

3 functions of rivers

Erosion

Transportation

Deposition

Slide 2

The Work of Rivers

Erosion

A river may erode in 4 ways

Abrasion/corrasion

Load carried by a river will grind against its bed and sides.

This process slowly wears the bed and sides away.

Slide 3

The Work of Rivers

Erosion

2. Attrition

When thrown against the sides and bed of rivers, the load gets broken into smaller pieces.

Slide 4

The Work of Rivers

Erosion

3. Hydraulic action

The work of turbulence in the water.

Running water causes friction in the joints of rocks in a stream channel

Joints may be enlarged

Loosened fragments of rocks get swept away.

Slide 5

The Work of Rivers

Erosion

4. Solution/Corrosion

Certain minerals in rocks like limestone can be dissolved in water.

Rocks are then eroded.

Slide 6

The Work of Rivers

Relationship of velocity and sediment size to erosion

Slide 7

The Work of Rivers

B. Transportation (4 ways)

Slide 8

The Work of Rivers

B. Transportation (4 ways)

Traction

Larger and heavier rocks/gravels are dragged or rolled along the bed.

Slide 9

The Work of Rivers

B. Transportation (4 ways)

2. Saltation (saltim: by leaps/jumps)

Smaller and lighter rock fragments and sand hop and bounce along the river bed.

At times, the distinction between traction and saltation may be difficult to determine.

Slide 10

The Work of Rivers

B. Transportation (4 ways)

3. Suspension

Some of the load like silt and clay (fine-grained) will float along.

They may only be deposited when stream velocity reaches near 0.

Turbulence in the water is crucial in holding a load of sediments.

Slide 11

The Work of Rivers

B. Transportation (4 ways)

4. Solution

Some minerals are transported in dissolved form.