Rivers in the upper course; Geography B

Typical landforms in upper courses:

Small rapids/waterfalls in upper course because of gradient.

Solution

transportation process: Dissolved load

Erosive process: Soluble rocks being dissolved

Solution

transportation process: Dissolved load

Erosive process: Soluble rocks being dissolved

Suspension

Transportation process: Small sediment held in river (near-ish to surface)

Saltation

Transportation process: ‘bouncing’ of particles too heavy to be suspended but too light to be rolled.

Hydraulic action

Erosion process: water is forced into cracks breaking up the bank

Hydraulic action

Erosion process: water is forced into cracks breaking up the bank

Attrition

Erosion process: rocks wear each other away as they knock together

Abrasion

Erosion process: Rocks wear away the river bed

First step of waterfall formation:

Waterfalls occur when a river crosses a bed of more resistant rock

Second step of waterfall formation

Erosion of less resistant rock undercuts the hard rock above it. River’s energy creates a plunge pool at the foot of the waterfall.

Fourth step of waterfall formation

The waterfall takes up a new position, leaving a steep valley/gorge

A river in it’s upper course flows slowly….

Because of friction with the bed

Transportation processes are?

Are how the river carries its load

Typical valleys in river’s upper course (in an upland area)

V-shaped valleys. Steep sides and a narrow bottom.

Interlocking spurs created how?

As the river (in upper course) cuts vertically into resistant Carboniferous limestone, it winds around areas of most resistant rock. This creates the interlocking spurs.

Interlocking spurs

Ridges that jut into the valley from both sides

Process involved in shaping a valley

Weathering processes: Physical/chemical/biological

Physical weathering:

When physical force breaks down rock.

E.G Freeze thaw weathering attacking outcrops of rock

Biological weathering

When plant roots/birds/animals/ break up rock

Chemical weathering

Is any chemical change causing the decay of solid rock.

Mass movement

The movement of weathered fragments downslope by gravity.

Can be rapid/slow.

Two examples of rapid mass movement

Landslides And Mudflows

Example of slow mass movement

Soil creep

Effects of soil creep

Less noticeable than rapid mass movement’s effects. Over many years can cause trees/ lampposts/walls to lean

Valley shape affected by what? Three examples:

• The rate it weathering

• the rate of mass movement

• how effectively river can remove material

What happens when the river has (high) energy?

It takes material and uses it to erode the valley, making it steeper

What happens when river flow is slow?

Weathered rock would then collect at the bottom of the slope, making the valley gentler and flatter