Hydrosphere Flashcards
Describe formation of a V shaped valley
V-shaped valleys are only found in hilly or mountain areas.
• Rivers flow quickly down the mountainside and erode the landscape vertically, creating steep valley sides that are shaped like a letter V.
• The valley sides are then attacked by weathering processes, such as freeze-thaw and biological weathering.
• The weakened valley sides eventually collapse or move down slope due to processes such as slumping or soil creep.
• The force of the water and the grinding rocks and stones cut down into the river bed to carve out a V-shaped valley between interlocking spurs.
• Interlocking spurs are areas of more resistant rock left behind because the river erodes softer rock quicker.
• Hydraulic action, corrasion and corrosion further erodes the valley sides and the characteristic V shape is created over time.
• Eventually, the valley becomes deeper and wider.
Describe formation of a waterfall
• Waterfalls form where water rushes down steep hillsides in upland areas and erodes the rocks.
• Hydraulic action of fast flowing water compresses air into the river bank causing materials to be dislodged.
• The force of the water throws bedload against the banks, causing erosion through abrasion.
• Solution also occurs when soluble rocks react with acids in the water, further weakening the banks.
• Differential erosion takes place over bands of more and less resistant rock/where harder rock is overlaying softer rock/bands of hard/soft rock.
• Some types of rocks (shale, for example) wear away more easily than others (such as sandstone or limestone).
• The river wears away the weak rock and travels across the surface of stronger rocks. These more resistant rocks become the capstones to waterfalls.
• Undercutting causes an overhang of the hard rock.
• Over time the hard rock is unsupported and collapses due to gravity into the plunge pool.
• Attrition can occur where the rocks in the plunge pool hit off each other, eroding them further.
• Over time, the waterfall retreats upstream.
• The height and number of waterfalls along a stream or river depends upon the type of rocks that are being eroded by the water
Describe a meander
• A meander is a bend, loop, turn, or winding in the channel of a river.
• A meander is produced by a stream or river swinging from side to side as it flows across its floodplain or shifts its channel within a valley.
• Water twists and turns around stones and other obstructions resulting in areas of slower and faster water flow.
• Water moving faster has more energy to erode. This occurs on the outside of the bend and forms a river cliff.
• The river erodes the outside bends through corrasion, corrosion and hydraulic action.
• Water moves slowly on the inside of the bend and the river deposits some load, forming a river beach/slip-off slope.
• Meanders are mostly found in the middle and lower courses of a river.
Describe the formation of an ox bow lake
After a long period of continual erosion, the meander in a river becomes very curved and deposition narrows the neck of the meander.
• Eventually the river cuts through the neck during a flood, cutting off the meander and forming an oxbow lake.
• The river continues on its straighter path and the meander is abandoned.
• The fastest current will now be flowing in the centre of the river channel and deposition is more likely to occur beside the banks.
• New deposition seals off the ends, and the cut-off becomes an oxbow lake that will eventually dry up.
describe input of the drainage basin
• Precipitation, mainly in the form of rainfall and snow, with the amount and duration having an impact on the level of water in the system.
storage of a drainage basin
Water is stored on the surface in lakes and rivers
Water can be stored underground in the groundwater store through the processes of infiltration and percolation.
• Water is stored in leaves and roots of vegetation with water also seeping into the ground by interception (ie, the storage of water on leaf and plant stems).
• Can be stored as soil moisture in the upper layers or deeper down in rock stores such as the water table.
• The amount of water stored will vary depending on the porosity of the soil and on the permeability of the rock.
transfer of drainage basin
• The sum of all the water flowing over the drainage basin’s surface is called runoff.
• Runoff is made up of streamflow, which is flow through permanent river channels, and overland flow or surface runoff.
• Overland flow transfers water through the basin either as sheetwash, across the surface, or in tiny channels called rills.
• Beneath the surface, water is transferred via throughflow - the movement of water through the upper soil layers towards the river, with the much slower groundwater flow taking longer to enter the river.
• Transfer also occurs through the movement of clouds bearing moisture by the process of advection.
• Water that has been intercepted by foliage may also be transferred, either directly as throughfall, or by running down branches and stems via stemflow.
output of the drainage basin
The most typical output of a drainage basin is surface runoff into the seas or oceans
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Some water can also be lost to direct evaporation.
• Moisture can be lost through plants withdrawing water from the soil via their roots
