chapter 11 rivers

Question 1

describe a river landform of erosion
(waterfalls)

Answer 1

a waterfall is normally found in the youthful stage of a river
its rate of erosion depends on the height, the discharge of the river and the type of rock it flows over

waterfalls develop when a river meets a band of soft rock after flowing over hard rock due to differential erosion the water quickly erodes the soft rock by hydraulic action and abrasion this steepens the gradient of the river

as the river hits the soft rock on the riverbed it carves out a deep hole called a plunge pool.

the running water also begins to under cut the soft rock below the hard rock causing an overhang. eventually the hard rock becomes unstable and breaks off into the plunge pool.

this process causes the waterfall to retreat upstream in a process called headward erosion. this results in a valley called a gorge.
eg Niagara falls.

Question 2

explain hydraulic action

Answer 2

this is the force of moving water

Question 3

abrasion

Answer 3

when a river uses the force of its load to erode

Question 4

attrition

Answer 4

the erosion of the load rather then the river bed or banks from the river load colliding with each other smoothing it down and making it smaller.

Question 5

solution

Answer 5

the chemical weathering of rock surfaces by water.

Question 6

depositional landform ox bow lake

Answer 6

An ox bow lake is a cresent shaped lake that is found beside a meandering river.
(river shannon)

by the lower stage of a river the meanders have gained much larger loops and the rivers course is far more twisting
hydraulic action and cavitation occur at the the sides of the bank causing the loops to get closer.

soon the neck of the of land between the meander becomes very small and in a flood when the river is at peak power it breaks through and flows along the straighter course.
deposition occurs here and cuts off the oxbow from the rest of the river

the oxbow then dries up and forms a scar or mort lake