(S6) Glacial Environments

Question 1

What is a “Nunatak”?

Answer 1

Protrusion of land above ice

Question 2

What is an “Ice Shelf”?

Answer 2

Floating ice from an ice sheet

Question 3

Where is the fastest flow in a valley confined glacier?

Answer 3

Center of the valley

Question 4

What is the primary mode of transportation of sediment in a cold based glacier?

Answer 4

Sediment largely from valley fallen detritus carried on surface

Question 5

What is the primary erosion and transportation regieme of a polythermal glacier?

Answer 5

PMP = glacial surges readily eroding bedrock which is released on retreat

Question 6

What is the primary erosive regieme of a temperate glacier?

Answer 6

Abrasion, plucking, rock-flour and large blocks of bedrock

Question 7

What is “supraglacial debris”?

Answer 7

Onto top from valley sides

Question 8

How is basal debris formed?

Answer 8

Abrasion and plucking

Question 9

What size of material is usually transported supraglacially?

Answer 9

Mostly coarse material from valley sides

Question 10

What size of material is usually transported subglacially?

Answer 10

Large range from rock flour to larger rocks

Question 11

How does internal deformation of a glacier effect basal debris?

Answer 11

May cause some basal debris to be brought up into the glacier body

Question 12

How do englacial and subglacial channels affect the transport regieme of a glacier?

Answer 12

Sorting of sediments inside temperate glaciers

Question 13

What is glacial till?

Answer 13

The direct deposit of (unconsolidated) rock by ice

Question 14

What is tillite?

Answer 14

Till which has been consolidated

Question 15

Where are melt-out tills found?

Answer 15

Front of glacier

Question 16

Where are lodgement tills found?

Answer 16

Debris which has been plastered at the base of ice during movement

Question 17

What are flow tills?

Answer 17

Accumulation of tills which have been reworked by gravity flows

Question 18

What are the characteristics of sediment which has been transported by laminar flow in a glacier?

Answer 18

No mixing or sorting

Question 19

What are the four main characteristics of glacially transported sediments?

Answer 19

No sorting, Angular, Material on top subject to weathering, Immature texture

Question 20

Name one common and one uncommon lithology found in glacial deposits

Answer 20

Common: Lithic Fragments, Uncommon: Clays

Question 21

What is an interesting feature about rock flour which is not common in all other sediment environments?

Answer 21

Retains it’s mineralogy as often not subject to chemical weathering

Question 22

Rock flour does not ___ and therefore stays in ___ much longer

Answer 22

Flocculate, Suspension

Question 23

What gives glacial melt its green colour?

Answer 23

Rock flour in suspension

Question 24

Why are continental glacial deposits rarely preserved in the long-run?

Answer 24

Most modern glacial environments subject to erosion and thus are reworked and removed

Question 25

What is the only thing commonly preserved from pre-quaternary glacial deposits?

Answer 25

Moraines

Question 26

What are the five forms of moraines?

Answer 26

Push moraines, Dump moraines, Lateral moraines, Medial moraines, Ice-cored moraines

Question 27

What are Push-Moraines?

Answer 27

Bull-dozer style

Question 28

What are Dump-Moraines?

Answer 28

Conveyor-belt type

Question 29

What are Ice-cored Moraines?

Answer 29

Moraines which may contain a core of ice which is insulated by debris

Question 30

How thick is a typical lodgement till?

Answer 30

10's m's thick

Question 31

How are ribbed moraines formed?

Answer 31

From the irregular ridges formed in lodgement tills

Question 32

How do drumlins form?

Answer 32

Deposition of lodgement till, reworked into elongate formations

Question 33

What are the typical dimensions of a drumlin?

Answer 33

Elongate axis towards flow - 10's m wide, 10's m to km long

Question 34

What is an esker?

Answer 34

Ridges elongate to the paleo-glacial flow - formed by deposition in subglacial rivers

Question 35

What are the typical dimensions of an esker?

Answer 35

m to 10's m high, 10's m to 100's m wide

Question 36

What bedform/sedimentary structure may be seen in an esker?

Answer 36

Bars: x-bedded and horizontally stratified lenses

Question 37

How are esker bars distinguished from river bars?

Answer 37

Eskers: lack of bank sediment and internal deformation common due to collapse of ice around the tunnel

Question 38

What is a karne/karne terrace?

Answer 38

Mounds/ridges from the collapse of crevasses/lakes/edge of glacier

Question 39

What is a sandur?

Answer 39

Glacial outwash plain

Question 40

How do rivers tend to act on an glacial outwash plain?

Answer 40

Braided

Question 41

How can a glacial outwash plain be identified in the geological record?

Answer 41

Associated with features such as moraines

Question 42

What features does a Jokulhlaup deposit usually have?

Answer 42

Massive beds, combination of poorly sorted or cross-bedded and stratified

Question 43

What type of sedimentary reworking commonly occurs on the outwash plane?

Answer 43

Winnowing from aeolian and fluvial reworking

Question 44

What are ventifacts?

Answer 44

Clasts which are exposed at the surface and abraided by windblown sediments

Question 45

What is the main source of marine glacial deposits at the poles?

Answer 45

Basal debris

Question 46

What is a tide-water glacier?

Answer 46

A valley glacier which reaches a marine environment

Question 47

What is created by ice which is locally grounded on the sea floor?

Answer 47

Grooves and tunnel valleys

Question 48

What are tunnel valleys?

Answer 48

Eroded valleys on the sea floor by increased density/pressure

Question 49

What are ice-proximal glaciomarine sediments?

Answer 49

Detritus which is released from the bottom of the ice sheets forming till sheets on the sea floor

Question 50

What are ice-distal glaciomarine sediments?

Answer 50

Material which is dropped by icebergs

Question 51

How can dropstones be confused in the geological record?

Answer 51

Similar deposits may be carried by vegetation

Question 52

What happens to the finer material released from icebergs?

Answer 52

Deposited as mud as it is transported in suspension

Question 53

What is the general consensus on immediate glacial deposits and hydrocarbon potential? (4)

Answer 53

Bad: Lack of organic material, poorly sorted, little sandstone, may not be preserved in the geological record

Question 54

What are the typical lithologies associated with glacial deposits?

Answer 54

Conglomerate, sandstone, mudstone

Question 55

What element of glacial deposits may have some hydrocarbon potential?

Answer 55

Outwash plains which have been sorted could be a potential to store

Question 56

What would be expected of the mineralogies of glacial deposits?

Answer 56

Variable, compositionally immature

Question 57

What would be expected of the texture of glacial deposits?

Answer 57

Extremely poorly sorted in till, poorly sorted in fluvial glacial

Question 58

What would be expected of the bed geometry of glacial deposits?

Answer 58

Bedding absent to indistinct in many continental deposits - may be laminated in glacio marine

Question 59

What sedimentary structures would be expected in glacial deposits?

Answer 59

Usually none in tills, cross-bedding may be found in fluvioglacial

Question 60

What paleoflow would be expected in glacial deposits?

Answer 60

Clast orientation for ice flow

Question 61

What would be expected of the sedimentary colouring of glacial deposits?

Answer 61

Variable, not usually oxidised

Question 62

What facies would be expected to be associated to glacial deposits?

Answer 62

Fluvial facies, Shallow marine