River Processes & Landforms (Edexcel IGCSE Geography): Flashcards
Exam code: 4GE1
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- FrontFluvial Processes
Define weathering.
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Define weathering.
Weathering is the breakdown of rock in-situ through physical, chemical or biological processes.
Physical weathering such as and exfoliation, occurs due to changes in temperature.
Physical weathering such as freeze-thaw and exfoliation, occurs due to changes in temperature..
What is slumping in the context of mass movement?
Slumping is a type of mass movement that occurs when a slope is undercut by a river, causing material to move rapidly down the slope, often where less resistant material overlies harder rock.
True or False?
Vegetation increases the amount of mass movement on a slope.
False.
Vegetation decreases mass movement because plant roots bind the soil together, holding the slope in place.
Define friction in the context of river processes.
In the context of rivers, friction is the resistance between the moving water and the bed and banks, which uses up most of the river's energy.
Most (about 95%) of a river's energy is used to overcome .
Most (about 95%) of a river's energy is used to overcome friction.
Why is there more friction in the upper course of a river?
There is more friction in the upper course because the river is shallow and narrow, so more water is in contact with the bed and banks, and the rocks are larger, increasing resistance to flow.
Define vertical erosion.
Vertical erosion is the process by which a river erodes downwards into its bed, increasing the depth of the river channel and valley, and is dominant in the upper course.
Define traction in river transportation.
Traction is the process where large rocks and materials are rolled along the riverbed.
When a river does not have enough energy to carry materials, it . This process is called .
When a river does not have enough energy to carry materials, it drops them. This process is called deposition.
What is saltation in the context of river transportation?
Saltation is when smaller material is lifted by the water and bounces along the riverbed.
True or False?
Suspension occurs when heavier rocks are rolled along the riverbed.
False.
Suspension is when lighter material is carried within the river flow. Heavier rocks rolled along the riverbed is called traction.
Define long profile.
A long profile of a river shows the changes in the river gradient from the source to the mouth.
True or False?
The gradient of a river is steepest in the lower course.
False.
The gradient is steepest in the upper course and becomes almost flat in the lower course.
Cross profiles show the of a river from one to another.
Cross profiles show the cross-section of a river from one bank to another.
What are two key differences between the upper and lower course cross profiles of a river?
The upper course cross profile has a narrow, shallow channel with steep valley sides, while the lower course has a wide, deep channel and flat floodplains.
Define vertical erosion.
Vertical erosion is downwards erosion of a river bed, making the channel deeper, and is most common in the upper course of a river.
The source of the River Tees is in the Pennines, and its mouth is at the .
The source of the River Tees is Cross Fell in the Pennines, and its mouth is at the Tees Estuary.
What landform is created where a river flows over hard rock (dolerite) and softer rock (limestone and sandstone) in the upper course of the River Tees?
A waterfall is created, specifically the High Force waterfall, where hard dolerite overlies softer limestone and sandstone.
True or False?
The lower course of the River Tees is dominated by vertical erosion and has a steep gradient.
False.
The lower course of the River Tees is dominated by lateral erosion and deposition, and has a very gentle gradient.
Define lateral erosion.
Sideways erosion of a river's banks, which widens the channel and dominates in the middle and lower courses.
Which landform develops in the middle course of a river due to increased lateral erosion?
Meanders.
In the upper course of a river, the bedload is ______ and levels of friction are high.
In the upper course of a river, the bedload is large and levels of friction are high.
Why were dams and reservoirs such as Cow Green built on the River Tees?
To supply water to the urban areas to the east and to control discharge downstream.
What was the purpose of the Tees Barrage?
To prevent flooding at high tides.
Define waterfall.
A waterfall is a steep drop in a river's course where water flows vertically, usually formed where hard rock overlays softer rock and erosion creates a step in the river bed.
The process of erosion is dominant in the upper course of a river, creating a -shaped valley.
The process of vertical erosion is dominant in the upper course of a river, creating a V-shaped valley.
What is the main process responsible for the retreat of a waterfall upstream?
The main process responsible for the retreat of a waterfall upstream is erosion of softer rock beneath hard rock (mainly by hydraulic action and abrasion), which leads to undercutting, overhang collapse, and the waterfall moving upstream.
True or False?
Interlocking spurs form in the upper course of a river as it meanders around areas of hard rock.
True.
Interlocking spurs are features created in the upper course where the river winds around more resistant areas of rock, resulting in a series of projecting ridges.
Define meander.
A meander is a large bend in a river formed in lowland areas where lateral erosion and deposition cause the river to curve across the valley floor.
The fastest water flow in a meander, known as the , occurs on the of the bend, leading to .
The fastest water flow in a meander, known as the thalweg, occurs on the outside of the bend, leading to erosion.
How is an ox-bow lake formed from a meander?
An ox-bow lake forms when erosion on the outside bends of a meander creates a narrow meander neck. During a flood, the river breaks through the neck, taking a straighter course, and deposition then cuts off the old meander, leaving an ox-bow lake.
Define levee.
A levee is a natural embankment formed along the edges of a river channel, created when the heaviest material is deposited first during flooding, building up raised banks.
Define plunge pool.
A deep pool at the base of a waterfall, formed as softer rock is eroded and undercut by hydraulic action and abrasion.
Define floodplain.
A flat expanse of land on either side of a river, formed by the migration of meanders and deposition during floods.
What forms on the inside of a meander bend where flow is slowest?
A slip-off slope, formed by deposition.
What is formed as a waterfall retreats upstream?
A steep-sided gorge.
On the outside of a meander bend, erosion undercuts the bank to form a ______.
On the outside of a meander bend, erosion undercuts the bank to form a river cliff.
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