unit seven: variation in glacial processes, landforms and landscapes over different timescales

Question 1

what are 3 time scales to examine how glacial landforms change over time

Answer 1

rapid, seasonal and long-term

Question 2

how can glacial landscapes change rapidly?

Answer 2

mass movement such as rockfall

Question 3

what is rockfall?

Answer 3

rapid, free-fall of rock from a steep cliff face. activated by freeze-thaw weathering, loosening the exposed rock

Question 4

what is an example of where scree slopes can be found in the uk?

Answer 4

nant ffrancon valley in snowdonia

Question 5

where did the randa rockslide take place?

Answer 5

switzerland

Question 6

when was the randa rockslide?

Answer 6

april 18th 1991

Question 7

what happened during the randa rockslide?

Answer 7

• around 15 million m3 of rock slid down the valley
• it was caused by intense freeze-thaw weathering
• total of 33 million m3 of rock fell 600m
• changed the profile of the valley in less than a day
• 33 buildings destroyed
• blocked a 1.3km-long stretch of vispa river

Question 8

what are fluvioglacial streams like in the summer?

Answer 8

more meltwater = bigger streams

Question 9

what are fluvioglacial streams like in the winter?

Answer 9

less meltwater = smaller streams

Question 10

how can fluvioglacial streams change daily?

Answer 10

impacted by the direction of the slope is facing, because facing towards the sun will result in bigger streams

Question 11

what do seasonal variations impact?

Answer 11

processes of transport and deposition vary

Question 12

what are 2 landforms where seasonal changes to fluvioglacial streams affect deposition?

Answer 12

• infilling of lakes as kettle hole lakes
• infilling proglacial lakes with varves

Question 13

how do varves form?

Answer 13

• winter = less meltwater = smaller clay and silt pieces
• summer = more meltwater = bigger pieces (finer material in suspension while big are deposited)

Question 14

what can varves tell us?

Answer 14

1) age
2) climate (how much sediment was deposited)

Question 15

why do varves occur?

Answer 15

changes in meltwater and velocity

Question 16

what ultimately may happen to kettle hole and proglacial lakes after a number of years, if varves continually form?

Answer 16

they will get filled with sediment and will slowly stop being a lake

Question 17

what are alluvial fans?

Answer 17

deposits of stream load at the base of a steep slope

Question 18

how do alluvial fans form?

Answer 18

• streams flow down the mountain areas with a lot of energy, due to steep gradient
• carry large amounts of sediment
• lower altitudes on flatter ground = velocity of stream is reduced = loss of stream energy
• as stream fans out it creates the familiar triangle-shaped feature

Question 19

what is an example of an alluvial fan in the uk?

Answer 19

beneath cwm coch in the nant ffrancon valley in snowdonia

Question 20

what is the apex of an alluvial fan?

Answer 20

the narrow point of the alluvial fan

Question 21

what is the fan apron of the alluvial fan?

Answer 21

the wide triangle

Question 22

how big is koshi river’s, in nepal, alluvial fan?

Answer 22

15,000 km2

Question 23

how are ribbon lakes infilled?

Answer 23

as the stream enters the lake, its velocity drops, resulting in the stream load being deposited

Question 24

what is a misfit stream?

Answer 24

the running water that drains the post glacial landscape will converge at the base of a glacial trough

Question 25

how does a misfit stream alter the shape of a glacial trough?

Answer 25

cuts downwards due to vertical erosion

Question 26

what is an example of a misfit stream?

Answer 26

the afon ogwen through the nant ffrancon valley