11.1 Rivers

Question 1

what are the four types of erosion

Answer 1

• hydraulic action
• abrasion
• attrition
• solution

Question 2

what is hydraulic action

Answer 2

• sheer power of the water as it smashes against the river banks
• air becomes trapped in the cracks of the river bank and bed, and causes the rock to break apart

Question 3

what is abrasion

Answer 3

when pebbles grind along the river bank and bed in a sand-papering effect

Question 4

what is attrition

Answer 4

when rocks that the river is carrying knock against each other. They break apart to become smaller and more rounded.

Question 5

what is solution

Answer 5

when the water dissolves certain types of rocks, eg limestone

Question 6

what is a drainage basin

Answer 6

area of land around the river that is drained by the river and its tributaries

Question 7

watershed def

Answer 7

the area of high land forming the edge of a river basin

Question 8

source def

Answer 8

where a river begins

Question 9

mouth def

Answer 9

where a river meets the sea

Question 10

confluence def

Answer 10

the point at which two rivers meet

Question 11

tributary def

Answer 11

a small river or stream that joins a larger river

Question 12

channel def

Answer 12

where the river flows

Question 13

four types of transportation

Answer 13

solution, suspension, saltation, traction

Question 14

traction def

Answer 14

large, heavy pebbles are rolled along the river bed. Most common near the source of the river as the load is larger

Question 15

saltation def

Answer 15

pebbles are bounced along the river bed, most commonly near the source

Question 16

suspension def

Answer 16

lighter sediment is suspended (carried) within the water, most commonly near the mouth of the river

Question 17

solution def

Answer 17

the transport of dissolved chemicals. this varies along the river depending on the presence of soluble rocks

Question 18

deposition def

Answer 18

when the river loses energy, it drops any of the material it has been carrying

Question 19

factors leading to deposition

Answer 19

• shallow water
• at the end of the river’s journey, at the river’s mouth
• when the volume of water decreases

Question 20

how does the river valley change going down the river

Answer 20

• sides become less steep
• gradient decreases
• shape of the valley changes from a V to U

Question 21

what is vertical erosion and what is it powered by

Answer 21

• vertical erosion is the deepening of the channel
• vertical erosion is powered by hydraulic action

Question 22

where does vertical erosion mostly happen

Answer 22

In the upper course; the little energy the river has left after friction caused by boulders in the river is used to deepen the channel

Question 23

what is lateral erosion and what is it powered by

Answer 23

• causes widening of the channel
• lateral erosion is most evident in the lower course of the river where the energy is the highest. Through hydraulic action and abrasion the banks of the river are worn away and the the river widens

Question 24

how does a rock change as it moves downstream

Answer 24

• attrition takes place along the river channel when rocks collide with one another
• the river current transports the load downstream, the large rocks moving through the process of traction
• over time further erosion leads to a more rounded pebble through the process of attrition or abrasion

Question 25

state two origins of the load found in the river

Answer 25

- weathered material that has tumbled down the hillside - eroded river banks

Question 26

state the general relationship between particle size and velocity at which a particle is deposited

Answer 26

- as particle size increases, the velocity of the river required to carry the load increases - when the river does not have enough energy to transport the load, it will be deposited on the river bed

Question 27

what is the graph that shows when a different sized particle will be transported called

Answer 27

Hjulstrom Curve