river landscapes and processes key revision points

Seite 1

drainage basin - an area drained by a river and its tributaries

source - where a river starts

mouth - where the river meets the sea

tributaries - small streams and rivers that join a larger river

watershed - te boundary of a drainage basin usually highland

confluence - a point at which two rivers meet

weathering

the breaking down of rocks in situ

erosion

the wearing away of the land/rock by the action of the rivers, ice the wind and the sea

biological weathering

seeds that fall into the cracks in rocks will start to when moisture is present. the roots force their way in to the cracks, increasing the size of the cracks. Burrowing animals such as rabbits widen the cracks further. this results in the rock breaking up.

physical weathering

water gets into the cracks of the rock. when the temperature drops below freezing t water will expand and increase the size of the cracks. overtime this causes the rock to weaken and so the bits break off.

chemical weathering

rain water contains weak acids that can react with certain types of rocks. the carbonates in limestone are dissolved by these weak acids. this causes the rock to break p and disintegrate

hydraulic action- pressure of the river or sea water being pushed against the banks and bed of the river

abrasion/corrasion- particles/load carried along the river rub against the river bed and river banks

corrosion - a chemical reaction between certain rock types and river water . the water wears the rock away

attrition- the rocks and pebbles hit each other and breack down into smaller peaces or wear away to form sand

suspension- fine light material is carried along the river

solution- minerals are dissolved in the water.this is a chemical change

traction-large boulders and rocks are rolled along the river bed

saltation- sall pebbles and stones are bounced along the river bed

deposition is when the river eaches flatter land or sea reaches the coast ,it loses its energy. as it loses energy it deposits its load which can create new landforms

mass movement

during dry weather the soil contracts making cracks

when it rains the water gerts into the cracks

eventually the soil becomes saturated withwater

this weaken the rock and due to the pull of gravityand the weight of the saturated soil it slips down the sope creating a slip plaine lavnig behind a curved surface.

Seite 2

the shape of the river changes from v shaped to u shaped as ou go downstream

in the highlands the river erodes vertically due to gravity. this creates a steep v shaped valley

downstream the river erodes laterally due to the lack of gradient

the width of the river increases as you downstream as the river gets more water form the tributaries which results in more energy which erodes the banks of the river.

the depth of the river increases as you go downstream the water fromthetributaries which results in more energy which erodes the river bed.

velocity the velocity increases as you go downstream as there is less friction as there is more discharge

the sourse of the river dee is 460 metres above sea level in the Snowdonia national park in wales

the average annual rainfall exceeds 3000mm and the runoff is very highfrom the steep upland slopes