Rivers🌊 Flashcards
(25 cards)
Physical Geography - Rivers
“Feature formation”
- V-Shaped valleys (upper course)
Stage 1 - In the upper course, a river
flows down steep slopes eroding the landscape vertically (1).
The river erodes a deep notch into the landscape using hydraulic action and corrosion (1).
Stage 2 - Abrasion is when the material carried along by the river scours and wears away the banks and bed of the river like sandpaper (1).
Hydraulic action is when the force of water gets into cracks and weaknesses in the rock, and breaks chunks off (1).
Stage 3 - This steepens the valley sides
as they are vulnerable to weathering which loosens material on the banks of the river(1).
The rocks which have fallen into the river aid the process of abrasion which leads to further erosion.
- Meanders (middle course)
Stage 1
In It’s middle and lower course, a river rarely flows in a straight line resulting in water flowing from side to side - meandering.
Stage 2
The water flows faster on the outside and erodes the outside bend of the river channel to form a river Cliff (1).
This wearing away of the river banks can be done by the process of abrasion, attrition or hydraulicacion (1p List).
Hydraulic action is where the force of the water gets into small cracks and forces pieces to beak off the river bed and banks (1).
Meanders
(Continued)
Stage 3
The river flows more slowly on the inside
bend and deposits some of it’s load to form a river beach (1).
Helicoidal flow transports material from the cliff to the beach making meanders bigger and causes them to move down stream (1).
Overtime continuous erosion of the outer bank and deposition on the inner bank forms a meander in the river (1).
“Describe a river and its valley on an OS map”
(6 marks)
River
• Direction of flow - a river will get wider, the closer it gets to the ocean (middle/ lower course)
• The width - compare how wide it is from two different points using the scale Mr Moore Showed us.
• Show where there is a meander using coordinates.
• Show where the river gets tidal using coordinates.
• Identify different features (e.g. mudflats/waterfalls)
• Tributary - small rivers that join on to the big river.
Valley
• describe the width of the valley.
• describe what it looks like (e.g. v-shaped valley or flat and open)
• The stage it is in (e.g: upper, middle or lower course)
What is the first stage of V-Shaped valley formation?
In the upper course, a river flows down steep slopes eroding the landscape vertically.
The river erodes a deep notch into the landscape using hydraulic action and corrosion.
What is abrasion in the context of river erosion?
Abrasion is when the material carried along by the river scours and wears away the banks and bed of the river like sandpaper.
This occurs in the second stage of V-Shaped valley formation.
What is hydraulic action?
Hydraulic action is when the force of water gets into cracks and weaknesses in the rock, and breaks chunks off.
This process contributes to the erosion of the landscape.
What happens to the valley sides in the third stage of V-Shaped valley formation?
The valley sides steepen as they are vulnerable to weathering, which loosens material on the banks of the river.
This process leads to further erosion.
How do fallen rocks contribute to river erosion?
The rocks which have fallen into the river aid the process of abrasion, leading to further erosion.
This occurs during the third stage of V-Shaped valley formation.
What happens in Stage 1 of waterfall formation?
Water flows over layers of hard and soft rock. Soft rock is eroded more quickly, leading to differential erosion, and a step is formed.
What occurs in Stage 2 of waterfall formation?
Erosion continues and a plunge pool is formed. Hydraulic action breaks off pieces of rock and corrosion erodes like sandpaper.
What happens in Stage 3 of waterfall formation?
Undercutting removes the soft rock from underneath the hard rock, leaving it unsupported. It will eventually fall into the plunge pool, causing the waterfall to retreat upstream.
What is meandering in rivers?
In its middle and lower course, a river rarely flows in a straight line, resulting in water flowing from side to side - meandering.
What happens to the water flow on the outside bend of a river?
The water flows faster on the outside and erodes the outside bend of the river channel to form a river cliff.
What processes can cause the wearing away of river banks?
The wearing away of the river banks can be done by the processes of abrasion, attrition, or hydraulic action.
What is hydraulic action?
Hydraulic action is where the force of the water gets into small cracks and forces pieces to break off the river bed and banks.
What happens to the river flow on the inside bend?
The river flows more slowly on the inside bend and deposits some of its load to form a river beach.
What is helicoidal flow?
Helicoidal flow transports material from the cliff to the beach, making meanders bigger and causing them to move downstream.
How is a meander formed over time?
Continuous erosion of the outer bank and deposition on the inner bank forms a meander in the river.
What happens in Stage 1 of the formation of an ox-bow lake?
The river is meandering across a valley and erodes laterally at the sides. The river flows faster on the outside bend, creating a river cliff. This wearing away is caused by abrasion, attrition, and hydraulic action.
What occurs in Stage 2 of the ox-bow lake formation?
The river flows slower on the inside bend and deposits material, forming a river beach. Repeated erosion and deposition narrow the neck of the meander. During a flood, the river has more energy and erodes through the neck of the meander.
What is the outcome in Stage 3 of the ox-bow lake formation?
The river flows on a new, straighter path and the meander is cut off.
The river deposits silt which seals off the meander to form an ox-bow lake
What characterizes Stage 1 of a river in its lower course?
The river is on its flood plain with a very low gradient. As the speed of the river slows down, it is mainly depositing material.
What occurs during Stage 2 of a river in its lower course?
When the river floods, a lot of silt is deposited on the river banks and less on the flood plain. Frequent flooding continues this build-up. When the river is flowing normally, it deposits in the river bed.
