UK River Landscapes Flashcards
What’s a Course (in river)?
Path of river as it flows downhill
Where is the Upper Course of the river?
Closest to the source of the river
Where is the Lower Source of the river?
Closest to the mouth of the river
As rivers flow downhill what do they form?
- Form channels and valleys
- Erode landscape, material is deposited
- Shape of valley & channel changes along river depending on if erosion had the most impact
What does the Long Profile of a river show you?
How gradient (steepness) changes over different courses
What does the Cross Profile of a river show you?
What a cross section of the river looks like
What is the Gradient and Valley and Channel Shape at the Upper Course?
- Steep gradient
* V-shaped valley, steep sides, narrow, shallow channel
What is the Gradient and Valley and Channel Shape at the Middle Course?
- Medium gradient
* Gently sloping valley sides, wider, deeper channel
What is the Gradient and Valley and Channel Shape at the Lower Course?
- Gentle gradient
* Very wise, almost flat valley, very wide, deep channel
What is Vertical Erosion?
- Deepens river valley= v-shaped
- Dominant in upper course
- High turbulence = rough particles against river bed = intense downwards erosion
What is Lateral Erosion?
- Widens river valley during formation of meanders
* Dominant in middle & lower courses
What’s does Weathering do?
Breaks down rocks on the valley sides
What is Freeze-thaw weathering and when does it happen?
•Happens at freezing point of water
•Water into rock with cracks
•Water freezes it expands =
pressure on rock
•Water thaws it contracts = releases pressure on rock
•Repeating this widens crack & rock breaks
What are the Processes of Erosion?
- Hydraulic Action
- Abrasion
- Attrition
- Solution
What is Hydraulic Action?
Force of water breaks rock particles away from river channel
What is Solution?
River water dissolves some types of rock (chalk, limestone)
What is Abrasion?
Eroded rocks picked up by river scrape, rub again channel, wearing it away
What is Attrition?
- Eroded rocks picked up by river smash together breaking into smaller fragments
- Causes particle size to decrease between rivers source & mouth
What is Transportation?
Movement of eroded material
What are the Processes of Transportation?
- Traction
- Suspension
- Saltation
- Solution
What is Traction?
Large particles (boulders) pushed along river bed by force of water
What is Suspension?
Small particles (clay,silt) carried along by water
What is Saltation?
Pebble-sized particles bounced along river bed by force of water
What is Solution?
Soluble materials dissolve in water, carried along
What is Deposition?
- River drops eroded material it’s transporting
* Happens when river slows down
Why do rivers Slow down and Deposit material?
- Volume of water in river falls
- Eroded material increases
- Water shallower
- River reaches its mouth
Where do Waterfalls and Gorges form?
Upper course of river
How is a Waterfall formed?
- Softer rock eroded by abrasion more than hard rock = ‘step’
- Water goes over step, erodes soft rock more
- Steep drop created = waterfall
How is a Plunge Pool formed?
- Hard rock undercut by erosion, now unsupported & collapses
- Swirled around at foot of waterfall, erode soft rock by abrasion = plunge pool
How is a Gorge formed?
- More undercutting = more collapses
* Waterfall retreats = gorge
How are Interlocking Spurs formed?
- Erosion is downwards = v-shaped valleys
- Rivers wind around hillsides
- Hillsides that interlock as river wind around them = interlocking spurs
What are Meanders?
Large bends in a river
How are River Cliffs formed?
- Current faster on outside of bend, river channel is deeper
- More erosion takes place on outside of bend = river cliff
How are Slip-Off Slopes formed?
- Current slower on inside of bend, river channel is shallower
- Eroded material deposited on inside of bend = slip-off slopes