Formation of an Ox-bow lake

Question 1

Point 1
(Ox-bow lakes form when…)

Answer 1

Ox-bow lakes form when meanders become cut off from the main river.

Question 2

Point 2
(As meanders continue…)

Answer 2

As meanders continue to migrate downstream, erosion by hydraulic action and abrasion continues at the outside bend

Question 3

Point 3
(This creates…)

Answer 3

This creates increasingly more pronounced meanders and the necks of the meanders become thinner.

Question 4

Point 4
(Hydraulic action is when…)
(Abrasion is when…)

Answer 4

Hydraulic action is when air is compressed in the riverbank causing materials to be dislodged.
Abrasion is when the force of the water throws bedload against the banks causing erosion.

Question 5

Point 5
(Deposition continues…)

Answer 5

Deposition continues at the inside of each meander with slip off slopes/river beaches buildings, further narrowing the neck of the meander

Question 6

Point 6
(Eventually, due to the narrowing…)

Answer 6

Eventually, due to the narrowing of the neck, the two outer bends meet and the river cuts through the neck of the meander

Question 7

Point 7
(This may be at…)

Answer 7

This may be at a time of flood when the velocity and erosive power of the river is greater.

Question 8

Point 8
(The water now…)

Answer 8

The water now takes the new, shorter route rather than following around the bend. As the river’s now flowing straight it will erode more in the centre of the stream.

Question 9

Point 9
(Deposition along…)

Answer 9

Deposition along the riverbanks gradually seals off the old meander bend forming a new straighter channel.

Question 10

Point 10
(The old meander bend…)

Answer 10

The old meander bend is left isolated from the main channel as an ox-bow lake. Over time this feature may fill up with sediment and dry up.