Hydrosphere Flashcards
Formation of a waterfall
As a river flows or will go over bands of herder more resistant rock on top of bands of softer less resistant rock. The softer rock erodes much quicker and easier than the hard rock
This erosion can happen thrip the process of hydraulic action which is when water and air are forced into cracks in the rock exerting extra pressure. An explosive blast then takes place which weakens the rock causing fragments to break off
Corrosion also occurs which is when weak acids in the river water start to dissolve minerals in the rocks and wash them away in solution due to a chemical reaction taking place
The river undercuts the hard rock and creates an overhang which become unsupported and collapses under its own weight, landing in a plunge pool below
After it collapses, some of the rocks are then swirled around the plunge pool which helps to deepen it through the process of abrasion. Abrasion is when rocks carried along in the river, hit against the bed and banks and starts to wear them away
The plunge pool is also deepened at times of high discharge as this is when hydraulic action is most powerful
The water fall has now retreated and moved upstream and this process repeats
Overtime this will cut a steep sided gorse into the hillside
Hydraulic action
This is when water and air are forced into cracks in the rocks causing them to exert extra pressure. An explosive blast then takes place that weakens the rock fragments causing them to break off
Corrosion
When weak acids in the river water start to dissolve minerals in the rocks and wash them away in solution due to a chemical reaction taking place
Abrasion
When materials such as rocks and sediment carried in the river, hit against the banks and bed of the river wearing when away overtime
Formation of a meander
A meander is a bend in the river
In a straight river channel pools and riffles will develop as the water twists and turns around large obstacles such as boulders. This leads to areas of faster and slower movement. Pools are areas of deeper water where there is more energy due to less friction. Riffles are areas of shallower water created by deposition of sediment carried in the river.
Once the pools and riffles have developed the river flows in a winding course going side to side. A corkscrew like movement known as helicoidal flow moves material from the outside of one meander to the inside of the next.
Faster flowing water has more energy to erode through processes such as hydraulic action which is when water and air gets is forced into cracks in the rocks and exerts extra pressure. An explosive blast takes place which weakens the rock causing then to break apart.
This occurs on the outside of a bend and forms a river cliff which is a steep bank. The outside of the bend is further eroded through process such as abrasion which is when materials carried in the river, hit and rub against the river banks and bed wearing them away.
Weak acids in the river water may also start to dissolve the rocks causing them to be washed away in solution. This is known as corrosion
Water moves slower on the inside of the bend and therefore has less energy so deposits some of its load. This leads to a gently sloping river beach being formed.
Continuous erosion on the outer bend and deposition on the inner bend cause the meander to become more extreme over time. It will shake shape overtime as well as migrate downstream
Formation of an oxbow lake
Meander answer
Overtime, continual lateral erosion and deposition narrows the neck of the meander
During flood conditions the river will take the shortest route and therefore breaks through the neck of the meander
The river will then continue on the new straighter path, abandoning the old meander
The meander will quickly lose speed and energy and therefore deposit its load, this cutting it off from the new river channel
This leaves an oxbow lake that will eventually dry up except during periods of heavy rainfall
Formation of a V-shaped valley
Rivers begin high up in the mountains so they flow very quickly downhill eroded the landscape vertically. This cuts a deep notch into the land through the process of hydraulic action which is when water is forced into cracks in the rocks exerting extra pressure. An explosive type blast then takes place which weakens the rocks causing them to break apart.
Abrasion also occurs which is when particles in the ricer rub and hit against the bed and banks of the river, wearing them away,
Weak acids in the water may also start to dissolve the rocks in the valley side and wash them away in solution due to a chemical reaction taking place. This is known as corrosion.
As the river erodes downwards the sides of the valley are exposed to freeze thaw weathering which loosens the surrounding rocks causing some to fall into the river and steepen the valley sides
The rocks which have fallen into the river hell to assist the process of abrasion
The river transports the rocks downstream and the channel becomes wider and deeper creating a b-shaped valley between interlocking spurs
Explain the hydrological cycle
The main input into the hydrological cycle is precipitation for example rain and snow
Water from oceans or rivers can be evaporated due to heat coming from the sun and warming the water, this is a change from a liquid into the gas water vapour
Water be also be lost to the atmosphere from vegetation through the process of transpiration
As the water vapour from these processes rise, they cool and condense to form clouds
Wind then moves these clouds inland through the process of advection. When these clouds are big enough they will produce precipitation
Some of the rainwater may be intercepted by vegetation which slows down the movement of water
If rainwater lands on an impermeable surface such as tarmac it will return to its water source as surface runoff
Rainwater that lands of soil will be infiltrated into the ground
Once in the soil some moves downhill through a process called through flow and some may percolate deeper into the soil
The percolated water then moves through permeable rocks as ground water flow
Name factors affecting hydrograph shape
- area, shape and slope
- types of rock
- soil type
- land use (urbanisation)
- vegetation
- drainage density
How does area, shape and slope affect hydrograph shape
- large basins receive more precipitation than smaller basins so larger run off into river
- the wider the shape of the basin the greater the run off and channel flow
- Chanel flow will be faster on a steep slope compared to a gently sloping area
- water will return to river quickly is steeper slopes
How does type of rock affect hydrograph shape
- permeable rocks let water pass through them allowing rapid infiltration
- impermeable rocks are water tight so don’t let water pass through, leading to rapid surface run off as no water infiltrates
How does soil type affect hydrograph shape
- this influences the rate of infiltration
- infiltration is greater on thick soils and less on thinner soils
- thinner soils lead to rapid surface run off and encourages flooding
- thicker soils lead to slow surface run off and little chance of flooding
How does land use affect hydrograph shape
- concrete and tarmac surfaces are impermeable
- heavy rainfall on these surfaces can lead to rapid surface run off and flooding causing towns and cities to flood
How does vegetation affect hydrograph shape
- areas with lots of vegetation are able to reduce impact of heavy rainfall due to increased interception which delays surface runoff
How does drainage density affect hydrograph shape
- lots of tributaries allows water to enter river quickly and takes quickest route to main channel rather than if it gets infiltrated into soil
