Evidence for past climates L2- L5

Question 1

LANDFORMS - Glacial cirques

Answer 1

Glacial cirques are concave landforms formed at the sources of mountain glaciers

Question 2

How are glacial cirques formed? (2)

Answer 2

1) Hollows are sheltered from heat - leads to accumulation of snow and ice and ultimately glaciers; enlarged by freeze-thaw weathering and glacial erosion

Question 3

How are glacial cirques used in climate reconstruction?

Answer 3

Ancient snowlines can be compared with present day snowlines, and temperature changes calculated

Question 4

What is crag and tail?

Answer 4

Asymmetric hills

Question 5

How do crag and tail form?

Answer 5

C+& are formed by the inflow of glacial sediments into a cavity produced in the lee of the rock obstruction, and hence have tails composed of unconsolidated sediments.

Question 6

What are morraine’s?

Answer 6

any accumulation of unconsolidated debris, sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice sheet.

Question 7

What are drumlins?

Answer 7

Oval mounds of glacial till, elongated parallel to the axis of ice flow.

Question 8

How do drumlins form?

Answer 8

formed by a successive build of sediment to create the hill (ie deposition or accretion)

Question 9

What are eskers?

Answer 9

sinuous ridges of glacial-deposited material

Question 10

How do eskers form?

Answer 10

when sediment carried by glacial meltwater gets deposited in subglacial tunnels,

Question 11

what are kames?

Answer 11

mounds of glacial deposited material

Question 12

how do kames form?

Answer 12

deposited on depressions on ice of retreating glacier, deposited on land as ice melts

Question 13

What are tuyas?

Answer 13

A tuya is a flat-topped, steep-sided volcano formed when lava erupts through a thick glacier or ice sheet. They are rare worldwide, being confined to regions which were covered by glaciers and had active volcanism during the same period.

Question 14

what are the sub-glacial characteristics of a tuya?

Answer 14

Steep sided (magma under ice cools quickly and doesn’t flow far) with magma characteristics associated with subaqueous environment.

Question 15

what are the sub-aerial characteristics of a tuya?

Answer 15

flat lying lavas of a lava pond, with magma characteristics associated with eruption in air.

Question 16

what are deserts?

Answer 16

Accumulations of wind-blown particulates

Question 17

How do deserts form?

Answer 17

Large continental sand dunes only develop where precipitation is <100 mm a-1
If precipitation >100 mm a-1, vegetation cover reduces sand movement and encourages soil development

Question 18

How are deserts used on climate reconstruction?

Answer 18

Fossil sand dunes currently found in areas of high rainfall indicate that rainfall has increased since dune formation

Question 19

What is palynology?

Answer 19

the study of plant pollen, spores and certain microscopic plankton organisms (collectively termed palynomorphs) in both living and fossil form.

Question 20

how is palynology used in climate reconstruction?

Answer 20

• Sediments may contain pollen grains (palynomorphs) derived from local/regional vegetation; analysis of abundance/type of pollen grains provides a picture of vegetation at the time of deposition.
• Different types of vegetation are specific to different temperature zones, e.g. palm trees versus tundra

Question 21

What are diatoms?

Answer 21

A diatom is any member of a large group comprising several genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world.

Question 22

How are diatoms used in climate reconstruction?

Answer 22

• Diatoms preserved in lake/ocean sediments;
• Sensitive to different environmental conditions reflected in variations in species abundance
• analysis of abundance/type provides a picture of water quality (e.g. salinity, nutrients, temperature) at time of deposition (fall to ground… core)

Question 23

CASE STUDY: use of diatoms in Tanginika - what was the purpose?

Answer 23

to reconstruct late holocene climate (meeker et al)

Question 24

CASE STUDY: Tanginika - what was the project?

Answer 24

• 109 m length lake core
• Location in lake chosen where shielded from terrigenous input
• Radiocarbon dating still to be undertaken
• Core sampled at 5 cm intervals, species abundance noted.

Question 25

CASE STUDY: Tanginika - What was observed?

Answer 25

• 5 shifts in diatom assemblages
• Shifts are abrupt, suggesting that the lake is sensitive to climate variations.
• e.g. zone 5, Cyclostephanos dominated. A large species, requiring large amount of silica to build its shell. High silica may indicate high run off, implying high precipitation.

Question 26

What are sedimentary rocks?

Answer 26

• Products of weathering and erosion of EXISTING rocks
• Resulting in sediments become rocks over time as the sediment compacts due to overlying material and pressure

Question 27

What is diagnostic rock?

Answer 27

a distinctive symptom or characteristic

Question 28

Examples of diagnostic rock (3)

Answer 28

Till/ boulder clay → Glacial
Coral Reef → Tropical Sea
Scree → frosty hillside

Question 29

What is non-diagnostic rock?

Answer 29

not characteristic of a particular environment

Question 30

Examples of non-diagnostic environments (2)

Answer 30

• Mud - can be found in rivers, oceans - doesn’t indicate which environment you’re situated in
• Sand - equally can be found in rivers, oceans, desert etc