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Distinctive landscapes II - Coggle Diagram
Distinctive landscapes II
Drainage Basins :
Area of land surrounding a river, where any rain falling eventually makes it way to that river
The area is called the river's catchment
Sperated by a boundary called a watershed, ridges of high land, water falling on either side will go to different rivers
Key features
Tributary - small river that joins a main river
Source - where a river starts
Mouth - where a river flows into the sea or a lake
Confluence - the point where 2 or more river meet
Water shed - the boundary between two drainage basins
The path of a river is called its course
Rivers have an upper, lower and middle course
The shape of the valley changes depending on the dominant process
Courses
Upper
V shaped valley/ interlocking spurs
Mountaneous
Not much water, low energy
Vertical erosion
Rocky bedload
Middle
Meanders
Valleys
Slightly wider and deeper
Lateral and veritcal erosion
More energy
Lower
Low gradient
Meanders
Widest area
Deepest
Floodplains and Levees
V-Shaped valley
Valley sides are exposed to weathering (freeze thaw), lose material is transported into the river creates a v shape
Interlocking spurs
In upper course, there is more vertical erosion
River cuts down into the valley to form a narrow steep sided V shaped valley
If there are areas of hard rock like basalt that are harder to erode, it will wind around them, taking the path of least resistance and eroding the less resistance rock like chalk
This creates interlocking spurs to land whcih link together like the teeth of a zip
Exmaple: Blue Mountains Australia
Example - Grand Canyon
A narrow valley with steeply sloped sides that appear similar to the letter v from a cross section, found in the uppercourse
Isn't alot of energy to erode in the upper course, low energy is predominantly graviational meaning that the river erodes vertically, deepening the river channel
This process repeats overtime
Waterfalls and Gorges
Waterfalls form where a river flows over an area of hard rock, followed by an area of soft rock
The softer rock is eroded more easily than the hard rock (differential erosion) by hydraulic action and abrasion more creating a step in the river
As water goes over the step, it erodes more and more, a steep drop is eventually created, a waterfall
The hard rock is eventually undercut by erosion, causing it to collapse due to gravity
The force of the water on the soft rock creates a plunge pool, the hydraulic action by the fast-flowing water in the plunge pool weakens the soft rock (splashback erosion)
Overtime, more undercutting case more collapses of the cap rock, abrasion by the broken lumps of rock in the plunge pool continues to erode the soft rock
Upper course
Example = Gulfoss, 70m deep and 3km long
Waterfall slowly retreats upstream, creating a narrow deepsided gorge, each time the rock ledge collapses, the waterfall retreats further as the process repeats
Waterfall is a cascade of water falling from a height, former when a river flows over a ledge
Meanders
Rivers develop large bends called meanders in the middle and lower courses
The current is faster on the outside of the bend (thalweg) because it's depper, less friction
More erosion, hydraulic action and abrasion, takes place on the outside, forming river cliffs
The current is slower on the inside becasue the cannel is shallower, more friction
Eroded material is deposited on the inside, forming slip-off slopes
Example = Mississipi
Oxbow lakes
As the process continues, meanders migrate become more pronounced with a tighter meander neck
During high periods of discharge, the water cuts across the narrow meander neck as water find the most efficient path
This creates a new channel whcih the river follows after the flood event is over, causing the old meander bend to be abandoned
The old bend is further detacthed through deposition, forming an oxbow lake, which overtime dries up due to evapouration, forming an oxbow scar
Example - Mississipi
Meanders also migrate throught the river valley
Flood plains
Flast area of land that flood
The floodplain is the wide valley floor, on either side of the river, which occasinally gets flooded
When a river floods onto the floodplain, the water slows down and deposits the eroded material
This builds up, making it higher
Meanders move across the floodplain making it wider
Meanders also migrate downstream, flattening out the valley floor
The deposition on slip off slopes, also builds up the floodplain
Levees
Levees are natural embankments along the edges of a river
During a flood, eroded material is deposited over the whole floodpain
The heaviest material is deposited closest to the channel
Over time, the deposited material builds up, creating levees along the edge of the channel
Example = London is on the Thames floodplain
Waves
Constructive
Strong swash
Carry large amounts of sediment
Formed by distant storms
Construct the beach
Destructive
Formed by a local storm that crashes down onto a beach
Powerful backwash
Removes sediment
Destroys beaches
Waves are steep and close together
Beaches
Formed by Deposition
Found on coasts between high water mark and low water mark. The highest and lowest point the sea level gets to
They're formed by constrcutive waves depositing material like sand and shingle
Sand beaches are flat and wide
Waves formation
Formed by wind transferring energy into the waves and the frictional drag of the wind 'rucking' the waves
Causes water molecules to move in a circular motion and are moved landward in the prevailing wind direction
Strength
Distance travelled
Strenght of the wind
Length of time over which the wind has blown
Waves break
Bottom of the wave touches the sand and slows down due to increased friction
Top of the wave remains unaffected, it moves faster than the base, so the wavelength decreases and topples over itself and breaks