4. UK Evolving Physical Landscape: River Landscapes and Processes Flashcards
What changes when a river flows downhill?
Shape of river valley and river gradient
What is the path of a river called as it flows downhill? How does this breakdown?
Course
Upper - close to source - steep - V shaped
Middle - Medium gradient, gently sloping, wider, deeper channel
Lower - close to mouth - gentle gradient, very wide
What changes over a River’s Course?
Form channels and valleys as flow downhill
Erode landscape - transport and deposit further down
Shape affected in places where erosion or deposition is dominant process
What is a River’s Long Profile?
Profile of the river through the upper, middle and lower courses
shows how gradient changes
What is a River’s Cross Profile? And what changes it?
Shows cross section of a river.
Vertical erosion - deepens river valley making V shaped - dominant in upper course - high turbulence causes rough angular particles to cause downward erosion
Lateral erosion - widens river valley during formation of meanders - dominant in middle and lower courses
What can you see along the River of Eden?
Many landforms of erosion and deposition typical to river landscapes
Explain River Eden landscape changes along its Course?
In North West England between Lake Distict and Pennines
145km long and Source in Pennine Hills
Upper Course - Source 600m above sea level - hard resistant rock - steep sided valley - vertical erosion - narrow river channel, therefore, discharge and flow is low - carries large angular stones
Middle - Sandstone, less resistant rock - easily eroded - river valley wider - sides are gentle slopes and gradient less steep - channel wider and deeper - sediment smaller and more sounded rocks compared to Upper
Lower - very wide valley - flat - high velocity flow - low friction from smooth sides - channel very wide and deep - material fine and well sounded - carried by suspension or solution
What happens when a river flows?
Erode material - transport - deposit downsteam
What helps Shape River Valleys?
Weathering
Freeze / Thaw - water in rocks - freezes - expands - pressure on rock - thaws - contracts and releases pressure - widens cracks - breaks up
What are the 4 processes of Erosion?
Hydraulic Action - force of water breaks rocks
Abrasion - carried rocks rub against channel and wear away - most common
Attrition - rocks picked up smash into each other and break - edges round off
Solution - river dissolves some types of rock e.g. chalk and limestone
What is Transportation?
Movement of eroded materials
Traction - Large boulders pushed along by force of water
Saltation - Pebbles bounced along by force of water
Suspension - Small particles (silt / clay) carried by water
Solution - Soluble materials dissolve and carried by water
What is Deposition?
When a river drops eroded material it is transporting
Happens when velocity reduces
Reasons i) Volume of water falls ii) Amount of eroded material increases iii) Water shallower e.g inside of bend iv) River reaches mouth
What are found in the Upper Course of a river?
Waterfalls and Gorges
What is a Waterfall?
Form where river flows over hard rock followed by softer rock
Hydraulic action erodes softer rock - STEP in river - becomes steep - waterfall
What is a Gorge?
Hard rock in waterfall under cut by erosion - rock collapses and material erodes softer rock at foot of waterfall - abrasion - creates plunge pool - more undercutting over time - more collapses - waterfall retreats and leaves steep side GORGE
