Erosion and deposition Flashcards
Erosion, definition, types, result
Definition: Movement of soil, mud, rock etc Types: Wind, water, ice and gravity Result: Landforms are created by the removal of rock and soil particles.
Deposition, definition, types, result
Definition: Laying down of eroded material. Types: Wind, water, ice Result: Landforms are built up by deposited material.
Rivers – what are they
features of erosion and deposition
Source, definition
Where a river starts, normally high up a mountain
Mouth, definition
– Where a river ends, normally when it flows into the sea
A river moves its load by:
Rolling large stones along the bottom of the channel
Carrying sand, mud and silt in suspension
Carrying minerals in solution.
The three parts of a river are:
Upper course
Middle course
Lower course
Upper course, tell me abt it
The highest section, found in mountains and valleys. Erosion is the main process. River erodes a V-shaped valley. Straight path. Steep downhill.
Middle course, tell me abt it
River becomes wider and deeper
Valley becomes wider and flatter
Less steep
River begins to meander (bend).
Lower course, tell me abt it
Gentle slopes. River flows more slowly. Valley is wide and almost level. flood plains. Large meanders and oxbow lakes. Deposition occurs
Longitudinal profile
visual representation of the height and length of the river, indicates the gradient
Cross profile
shows the shape of the valley at an imaginary line drawn across the river
cross profile of upper course of a river
v
cross profile of middle course of a river
u
cross profile of lower course of a river
_
what does vertical erosion do?
what happens when rivers turn around obstacles of rock?
what does lateral erosion do?
deepens the valley.
interlocking spurs are formed.
widens the valley floor.
what is a gorge?
what is a canyon?
very deep, steep-sided valley formed by an energetic river in a humid environment.
very deep, steep-sided valley formed by an exotic river in an dry area.
Waterfalls and rapids
A resistant layer of rock across the course of the river can lead to a sharp change in the gradient and the formation of either a waterfall or rapids.
Fluvial landforms formed by deposition
The river will deposit its load as it begins to lose energy and to slow down. This can occur in the following situations:
Speed of the water decreases.
Volume of the water decreases.
Channel of the river becomes wider.
Load of the river increases.
The fertile material deposited by a river is called alluvium.
Alluvial fans
Alluvial fans form at the base of mountains when a river that is carrying a lot of sediment flows onto the flatter plain.
The sediment is deposited in the shape of a fan and the river splits into distributaries to flow round the deposited material.
Floodplain
the river becomes a wide, flat floodplain with a very gentle gradient. Numerous depositional landforms can be found on the floodplain
Meanders
A meander is a bend in a river.
Erosion occurs on the OUTSIDE of bends.
Deposition occurs on the INSIDE of bends
Oxbow lakes
As the outer banks of a meander continue to be eroded, the 2 outer bends meet and cuts through the neck of the meander.
Water takes the shortest route and doesn’t go round the bend.
More deposition is laid and the meander is cut off.
Delta
The river slows down as it enters the sea and deposits its load at the mouth of the river.
The deposited sediment at the mouth of the river builds up from fertile, flat landforms called deltas. The river splits into distributaries in order to flow through the deposits and reach the sea.
Soil
A thin layer on the surface of the Earth
Natural erosion
– soil removed naturally by wind and water movement
Natural erosion takes place at the same rate as?
soil is formed.
Topsoil
Has the most nutrients, often the first to be removed by erosion.
Humans contribute to soil erosion in which 3 ways?
agriculture
construction
mining
what are six ways agriculture contributes to soil erosion
overgrazing lack of crop rotation farming on a slope removing trees surface irrigation using pesticides/chemical fertilizers
Agriculture - solutions
Contour ploughing and leave unploughed grass strips between ploughed lands.
Drip irrigation
Avoid overgrazing
Allow indigenous plants to grow that will bind the soil.
Limit the use of pesticides and fertilisers.
Use crop rotation system.
Construction, how does it contribute to soil erosion?
Land is cleared for buildings or roads, soil is exposed and eroded.
When roads, factories, e.t.c, large areas of land are covered by tar and concrete.
These surfaces cannot absorb the rain and increases run-off.
Run-off in urban areas = contaminated with fuel, oil and other chemicals.
Construction vehicles compact soil, increases run-off.
soil and sediment carried from construction sites bury plant and animal habitats needed for healthy rivers and wetlands.
how does Mining contribute to erosion?
rock and soil are disturbed by drilling or earth moving.
Water is contaminated by poisons and chemicals from the mine
Open cast mining destroys landscapes, forest and wildlife habitats at the site of the mine
