Theme A: The Dynamic Landscape Flashcards
Name each input, store, transfer and output of a river and its meaning
- Inputs
Precipitation - any water falling from the sky; rain, snow, sleet, hail - Stores
Interception (by vegetation) - leaves and grass catch raindrops as they fall and store them. - Transfers
Surface run off/overland flow - water running over surface of ground
Infiltration - water sinking into soil
Through flow - water flowing through soil
Percolation - water sinking down through rock
Groundwater flow - water flowing slowly from rock to river - Outputs
Discharge - water flowing away in the river
Evaporation - water turning to water vapour in the air
Define each aspect of the drainage basin
Source - where the river begins
Tributary - small stream flowing into main river channel
Mouth - where the river flows into the sea
Watershed - boundary surrounding the drainage basin
Confluence - where to streams or rivers meet
Explain the changes which happen along a river including the meaning, change and why it happens
- Gradient
Meaning - steepness or slope the river flows down
Change downstream - gets less steel
Why? - river does more vertical erosion near source and more lateral erosion near mouth - Depth
Meaning - measure of water from top of water to river bed. Average
Change downstream - gets deeper
Why? - vertical erosion - Width
Meaning - distance from one side of river to other
Change downstream - gets wider
Why? - lateral erosion - Discharge
Meaning - amount of water at a point at certain time. Cumecs or cubic metres per second
Change downstream - increases
Why? - more water from tributaries and water flows faster with less friction - Load
Meaning - material river is carrying, rocks, pebbles, mud
Change downstream - smaller and more rounded
Why? - rocks knock against each other and break up. Sharp edges get knocked off.
What are they three main processes carried out by a river? Explain each one
- erosion - breaking up and removing rocks and soil
- transportation - carrying the load along
- Deposition - dropping the load the river was carrying
What are the four processes of erosion in a river?
- Abrasion/corrasion - by scraping the load it is carrying against the rock. Think of an emery board on your fingernail
- Attrition - pieces of rock hit against each other and break up
- Corrosion/solution - water dissolves minerals in the rock
- Hydraulic action - by the force of the water
What are the four processes of transportation in a river?
Traction - rolls the heaviest rocks along the river bed
Saltation - medium sized rocks bounce along the river bed
Suspension - smallest particles carried along by the water
Solution - some chemicals dissolve in water
Explain the process of deposition
This happens when the river slows down, it has less energy so it has to drop its load.
The heaviest material is dropped first
Most likely will happen when a river reaches the sea or a lake
Explain the formation of a waterfall
- a waterfall is formed when there is a layer of hard rock on top of a layer of soft rock
- the river erodes the softer rock more quickly so there is a step in the river bed, eventually this becomes deeper forming a waterfall
- hydraulic action and abrasion make a plunge pool at the bottom of the waterfall
- more erosion undercuts the hard rock leaving an overhang above the plunge pool
- the overhang of hard rock eventually collapses into the plunge pool and eventually a steep-sided gorge is formed as the waterfall retreats upstream.
Explain the formation of a meander and label the cross section
Outside bend
- water flows faster around the outside bend
- lots of energy eroded the bank moving it back
- erodes the river bed making it deeper
- erosion
- river cliff
Inside bend
- slower water
- less energy
- shallow water
- deposition
- slip off slope
Cross section from inside to outside bend;
- slip-off slope
- shallow water
- deep water
- river cliff
Define and explain the formation of a flood plain
Label and define each part of the cross section
A flood plain is flat land on either side of a river that will be covered with water if the river bursts its banks
Where there are meanders, the river flattens the land by eroding it and depositing sediment on it making a flat floodplain.
The water slows down, loses energy and deposit is load called sediment or alluvium which is fertile - good for growing crops
- river channel
- bluff, remains of higher land where the rest has been eroded
- floodplain
- deposition,process where flood water drops material its carrying
Give an overview of wave action at the coast
Coastlines are dynamic meaning they change overtime.
Wave action is the main process that causes this.
- destructive waves attack the coast
- constructive waves add sediment to the shore
The type of wave that breaks on the shore can be either one of these depending on the wind speed and how far the waves have travelled.
When the wave breaks;
- water surges up the beach (swash)
- them returns down the beach to the sea (backwash)
Explain the differences between the two wave types. Include; - size - frequency - season - effects
1. destructive waves Size - high and close together Frequency - frequent, up to 15 per min Season - common in winter (storm waves) Effects - stronger backwash than swash, drags sand and pebbles to sea, erodes coast
2. Constructive waves Size - low and far apart Frequency -less frequent, 6-9 per min Season - common in summer Effects -strong swash and weak backwash, pushes sand and pebbles up the beach, causes deposition which builds up the coast
Explain the erosion processes at the coast
- Hydraulic pressure - the force of waves alone especially in storm conditions
- Abrasion (corrasion) - the sand papering action of water carrying sand and pebbles - it smooths and wears away rocks where waves hit at the base of the cliff
- Solution (corrosion) - chemical action of sea water dissolving rocks such as limestone
- Attrition - occurs as pebbles transported by waves hit against each other breaking into smaller and rounded particles
Explain transportation and deposition at the coast
Pieces of rock eroded by the sea are transported by wave action. If waves approach the shore at an angle swash carries the material up the beach at the same angle but backwash returns if straight back to the waters edge because of gravity.
This zig-zag movement at the coast is called longshore drift
Deposition - when waves are constructive they deposit the load they carry on the shore this often happens in a sheltered bay between two headlands.
Explain how wave cut platforms are formed at the coast and what type of landform they are
- When destructive waves approach a rocky headland, hydraulic pressure and abrasion erode a wave cut notch.
Erosional landform - Through time the notch gets bigger and unsupported rock above it is undercut and collapses into the sea forming a cliff.
- Continued erosion and repeated collapse causes the cliff line to retreat. This leaves an almost level area of rocks and rock pools known as a wave cut platform at the base of the cliff e.g Portstewart Strand
