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Landforms of the upper valley - V-shaped valleys and waterfalls

Landforms in upland regions are dominantly created by erosion processes, where land is worn away.  Generally, the volume and discharge of rivers in upland regions tends to be low, and the river uses much of it's energy in overcoming friction.  The erosion direction here is vertical, or straight down into the bed of the river.  This has the effect of destabilising the slopes on either side of the river, creating a steep landscape. As shown below, near to the Kunar River in Pakistan.

Kunar River in Pakistan

Landforms in the Upper Valley

Waterfalls 

Niagara Falls     Waterfalls image 
Niagara falls, one of the worlds most famous waterfalls, but not in  the upper reaches of it's river! Above is a diagram showing the formation of a waterfall.  You can see an animation by clicking here. 

Waterfalls are one  of the most spectacular landforms found in the upper valley and are created by erosion processes.
They occur where a band of hard rock (e.g. granite) overlies a softer rock (e.g. clay).

Erosion processes such as Hydraulic Action (the force of the water) and Abrasion (where the river rubs stones that are being transported against the bed of a river thereby breaking it down) dominate.

The softer rock is eroded quicker than the harder rock and gradually washes away downstream.

This creates a plunge pool where water is swilled around, potholing can occur here and any rocks and debris swept into the plunge pool by the river will be swirled around and rub against the bed and banks of the plunge pool (called corrasion), deepening it further.

Over time, the softer rock is eroded further creating an over hang of hard rock.  This overhang is unstable as it's weight is unsupported.

Eventually, this hard rock collapses because it is unsupported and the waterfall moves back upstream.

This creates Gorges, which are steep sided deep river valleys.  This process will repeat continually, with the location of the waterfall moving back upstream.

V shaped valleys and interlocking spurs 

V-shaped valley diagram 

Vertical erosion processes wear away the rock in upper valleys.  As can be seen above, V-shaped valleys are a RONSEAL word - they describe exactly what is in the tin!

As the river erodes vertically down over it leaves behind valley sides that are shaped like a letter V.  This is because as it erodes straight down it leaves very steep valley sides that are then attacked by weathering processes such as freeze thaw and biological weathering.  This weakens the valley sides which may collapse or move down slope due to mass movement processes such as slumping or soil creep.  The river can then erode this material and move it away, leaving behind the characteristic V shape.

In addition, the river valley may also contain interlocking spurs, slivers of land that interlock.  Interlocking spurs are areas of more resistant rock left behind because the river erodes softer rock quicker.  The river moves between the interlocking spurs.

Tasks 

1) Find out about upper landform features from the BBC and take a test

2) Using the maps below describe the shape of each land form and explain why they take that shape on the map

V-shaped valley map  Waterfall map 
V-shaped valley map  Waterfall map 

3) Play a rivers Penalty shoot out game from Juicy Geography!