Mass Balance, Transport and past glaciations

Question 1

Mass balance (b)

Answer 1

= accumulation (c) + ablation (a)

Question 2

Mass balance (b) = accumulation (c) + ablation (a) 
Positive mass balance

Answer 2

More accumulation than melting

Glacier advance

Question 3

Mass balance (b) = accumulation (c) + ablation (a) 
Negative mass balance

Answer 3

More ablation than accumulation

Glacier retreat

Question 4

Measuring mass balance
Manual collection of mass balance
Accumulation zone

Answer 4

Pits (to check how much snow has fallen)

You can dig down into the glacier and see how much snow is deposited each year (quite easy to see)

Question 5

Measuring mass balance
Manual collection of mass balance
Ablation zone

Answer 5

Stakes

You can dig down into the glacier and see how much snow is deposited each year (quite easy to see)

Question 6

Positive mass balance measurements are very…

Answer 6

detailed

Question 7

Negative mass balance measurements are very…

Answer 7

very slow and expensive, small scale

Question 8

Positives of remote sensing

Answer 8

potentially cover large huge areas, could be semi automatic

Question 9

Negatives of remote sensing

Answer 9

may be problems with technique on small glaciers

Question 10

What is Global Land Ice Measurements from Space (GLIMS) used to do?

Answer 10

Using the World’s Glaciers to Monitor Climate Change

Question 11

Glacial transport paths

Answer 11

Supraglacial
Englacial
Subglacial

Question 12

Sediment sources

Answer 12

Supraglacial debris
Subglacial debris
- Regelation
- Shearing
- Freezing on

Question 13

Pressure melting point

Answer 13

The pressure melting point is the temperature at which ice melts at a given pressure.

Question 14

Positive mass balance

Answer 14

More accumulation than melting
Glacier advance
There is more accumulation than melting so glacier advance

Question 15

Negative mass balance

Answer 15

More ablation than accumulation than accumulation
Glacier retreat
More ablation meaning the glacier retreats
The glacier is always moving forward (but it may retreat)
In the summer, the snow melts back at the front
In the higher part there is more accumulation (accumulation dominant)
The lower part is more ablation (called ablation dominant)

Question 16

Transport

What does englacial mean?

Answer 16

When material passes through the glacier
When it pass along the base it is sub-glacial
When material travels along the top it is supraglacial

Question 17

Transport

What does regelation mean?

Answer 17

Means refreezing

Water has to flow up hill which causes melting and then it refreezes when it gets to the other side

Question 18

Transport

What does shearing mean?

Answer 18

When there is a crack in the ice at the bottom and then there is sediment the protrudes into the base of the ice

Question 19

Transport

What does freezing on mean?

Answer 19

Where sediment gets frozen onto the glacier because it is so cold

Question 20

What is the Anglian?

Answer 20

a line that differentiates where the glacier was

Question 21

When was the most recents ice age in the uk?

Answer 21

10,000 years ago

Question 22

What did the recent ice age create?

Answer 22

Boulder clay deposits in eastern UK

Question 23

What was the Pleistocene?

Answer 23

A glacial period around 25,000 years ago when 30% of the earth’s land surface was covered by ice (mainly in the N. hemisphere) and most of Britain was covered by ice that had extended South from the Arctic in a colder glacial period.

Question 24

How did the Pleistocene end?

Answer 24

When the climate warmed (about 10,000 years ago)

Question 25

What is the ice sheet that covered the UK?

Answer 25

Devensian/ The Scandinavian

Question 26

Describe the maximum extent of the ice covering the UK 25,000 years ago

Answer 26

The ice covered The Wash in the East and South Wales in the West

Question 27

What are the 5 glacial processes?

Answer 27

1) Freeze-thaw weathering
2) Glacial Erosion
3) Movement
4) Transport
5) Deposition

Question 28

What causes freeze-thaw weathering?

Answer 28

Temperature changes
Moisture changes
Chemical processes by mild acid

Question 29

Describe the freeze-thaw weathering process

Answer 29

1) Water seeps into cracks in a rock face
2) The temperature falls at night, causing the water to freeze
3) Water expands - this expansion puts pressure on either side of the crack , causing it tear wide open
4) During the next 24 hour cycle, the ice melts, sinks deeper into the crack and freezes again
5) Over time, large blocks of rock can be shattered apart by repeated cycles of this weathering process

Question 30

What is the evidence for freeze-thaw weathering?

Answer 30

Scree slopes and blockfields (rock debris which cover large upland areas)

Question 31

Why is freeze-thaw weathering important?

Answer 31

It helps to shape jagged glacial mountain landscapes

Question 32

What are the two main ways in which ice is eroded?

Answer 32

1) Plucking

2) Abrasion

Question 33

What is plucking?

Answer 33

When ice moves over the rock surface and meltwater freezes around loose sections, pulling them away. It’s effective when the rock contains many joints (cracks) which the rock can seep into

Question 34

What is abrasion?

Answer 34

Caused by rocks and boulders embedded in the base of the glacier which act like sandpaper, scratching and scraping the rocks - causing striations

Question 35

Glaciation of Britain – glacial and inter glacial

Answer 35

Many potential glaciations

• A lot of potential glaciations with little evidence
• Old glaciation – Anglian 450ka
• Young glaciation – last glacial maximum (LGA) or Devensian 18ka

The glacier extent is disputed – more recent research suggests it stretched further into the north sea
British and Irish ice sheet (BIIS)
Most recent – Lock Lomond / Younger Dryas (12.9 – 11.5ka) – it becomes cold again for about 1,000 years and glaciers re-grow in mountainous areas
Cullins, Skye – you can see where the glacier was and the moraine at the front