Rivers Flashcards
Upper course features and processes
Features: Steep, V-shaped valley, waterfalls, and rapids.
Processes:
Vertical erosion deepens the valley.
Transport of large materials (boulders, rocks).
Occasional deposition in quiet areas.
Landforms: Waterfalls, V-shaped valley sides.
Middle course features and processes
Features: Wider, flatter valley with meanders and floodplains.
Processes:
Lateral erosion widens the valley.
Transport of smaller materials (sand, gravel).
Deposition along riverbanks (floodplains).
Landforms: Meanders, oxbow lakes.
Lower course
Features: Wide, flat valley with large river channel and floodplains.
Processes:
Limited erosion, mostly lateral.
Fine materials (silt, clay) are transported.
Deposition forms floodplains and deltas.
Landforms: Floodplains, delta.
Processes of erosion-2 types
Vertical and lateral, change river channel and valley as river flows downstream
Hydraulic action
Force of water hitting river bed and banks
Abrasion
Load carried by river hits the bed or banks, dislodging particles
Attrition
Stones carried by the river knock against each other becoming more smaller and rounded
Solution
Alkaline rocks e.g limestone, are dissolved by slightly acidic river water
Interlocking spurs-how they are formed(Erosion landform)
Formation:
In the upper course, the river erodes the landscape through vertical erosion.
The river winds around hard rock areas, leaving areas of land that protrude into the valley, called interlocking spurs.
These spurs “interlock” as the river meanders around them, forming a zigzag pattern.
Waterfalls-how they are formed(Erosion landform)
Formation:
Waterfalls form when a river flows over hard rock and then soft rock underneath.
The soft rock erodes faster than the hard rock, creating a drop in the river, forming a waterfall.
Over time, the erosion at the base creates a plunge pool, and the waterfall retreats, forming a gorge.
Gorges-how they are formed(Erosion landform)
Formation:
Gorges are formed when a waterfall retreats due to erosion at the base.
As the waterfall erodes the rock behind it, it leaves a steep-sided gorge.
The process of abrasion and hydraulic action deepens the gorge over time.
Meanders-how its formed(depositional)
Formation:
Meanders form in the middle course of a river where the flow is less steep.
Lateral erosion on the outer bend (where the water flows faster) and deposition on the inner bend (where the water flows slower) causes the river to curve.
Over time, this creates a winding pattern known as a meander.
Oxbow-lakes-how its formed(depositional)
Formation:
When a river meanders, it can form a sharp bend.
Erosion on the outer bend and deposition on the inner bend causes the meander to become more exaggerated.
Eventually, the river may cut a new, straighter path, isolating the old meander and forming an oxbow lake.
Floodplains-how its formed(depositional)
Formation:
Floodplains form in the lower course of the river where the valley is wide and flat.
When the river floods, it deposits fine silt and clay across the floodplain, creating a flat, fertile area.
Over time, repeated flooding and deposition build up the floodplain.
