Glaciers Flashcards
Glacier
moving mass of ice that begins on land
Glaciers form when
there is a year to year snow surplus
Firn
snow that survives a full season of ablation, partially compacted
Cold glacier
Glacier which is frozen to the bed rock and no erosion
basal sliding
glacier sliding over the bed before it due to melt water under the ice
Alpine glaciers form in
narrow mountian valleys
Alpine glaciers start as
cirque glaciers
piedmont glaciers
steep valley glaciers spill into realitively flat plains into bulb like lobes
Continental glaciers Shape
Dome
continental glaciers grow from
centeral accumulation zone
examples of continental glaciers
antartica, greenland
Accumulation zone
Upper part of glacier
Accumulation zone has a + or - mass balance
+
What causes flow (glaciers)
Annual Accumulation> Ablation
Ablation zone
Lower part of glacier- net loss from melting, calving
Negitive mass balance caused by
Ablation> accumulation
Equilibrium line
(~firnline) separates the two zones
ELA
Equilibrium line altitude
Vertical layers in a glacier
Brittle, plastic, basal
Brittle zone
at the top where crevasses form
Plastic zone
center
Melting (basal zone)
On upward slope
Refreezing (basal zone)
downward slope
Glacial erosion- Ice push
Glaciers push debris
Glacial erosion - Abrasion
Scouring by ice and embedded sediment
Glacial erosion - Plucking
Suction-like removal of blocks of ice
-exploits existing fracture/ joints in rock.
Glacial Erosion (3)
Icepush
Abrasion
Plucking
Small erosional features (glacial)
Polish
Striations
Grooves
Crag and tails/ Rat tails
Roches Mountonnees
Asymmetrical Rock knobs
Polliished, gentle stoss side (abrasion)
Rough steep lee side (plucking)
Alpine Erosional Landforms (7)
Cirques Glacial troughs Hanging valley Truncated spur Fjord Arete Horn
Cirques
result of alpine glaciers usually contains a tarn
glacial troughs
U-shaped valley
Relatively straight
Truncated spur
Large ridge of land with its end cut off
Fjord
drowned valleys flooded by rising sea
Arete
think ridge formed from when two glaciers erode parrell u-shaped valleys
col
Low part of an arete
Horn
Un affected glacial area
Nunatak
horn protruding from a glacier
Positive Continental erosional landforms
rock drumlins
drumlins
flutings
Negitive Continental erosional land forms
Mega- grooves/ mega flutes
rock basins
Depositional landforms by (glacial ice)
till
Depositional landforms by glacial melt water
stratified drift
Depositional landforms by glacial deposits
Glacial drift
End morains
Front of glacier
Lateral morains
beside glacier
terminal mark
the furthest advance
recessional mark
temporary halts or readvances during retreat
medial morains
between 2 coalescing glaciers
ground moraine
Under the glacier- Cover the ground in the path of the glacier
Drumlins
Streamlined hills of mostly till (tear dropped shaped- Steep side up glacier) Occur in groups (swarms or feilds)
Flutings
Highly elonglated drumlins ( no well devloped stoss and lee ends)
Glaciofluvial landforms
Produced by meltwater streams near glaciers
Sediment deposits called out wash
invariably in braided streams (high sed load, variable discharge)
Outwash plains
Broad plains formed by deposits from proglacial braided streams; very wide and active
Feed large glaciofluvial deltas
when dry becomes one main source of fine wind blown material called loess
eskers
sinous ridges deposited in streams in tunnels under the ice
kame
Formed in glacial cracks of sediment when glacier retreats it is deposited
proglacial lakes
Dammed by ice or moraine
Striking turquoise colour due to glacial rock flour
Deltas
Form where streams enter proglacial lakes
large thick sandy gravel deposits
Kettles
Depressions produced by melting iceblocks surrounded and or burried by outwash( or till)
later often occupied by a lake
Glaciolacustrine land forms:
Proglacial lakes
deltas
kettles
Glaciofluvial landforms
outwash plains
eskers
kames
Basal till
Unsorted matrix supported, over-consolidated, sub angular to sub rounded clasts,often cohesive(clay-rich), strong till fabric, striated clasts
Ablation till
Coarser less compact, more angular clasts, no fabric. May be crudly stratified
Glaciofluvial deposits
like braided river sediments, but deposits often much thicker. Commonly disturbed due to loss of ice support
Glacioacustrine deposits
Fine (claey to sandy muds), well sorted, finely stratified (often varved- annual sandy summer alternating with clay winter beds) Unconsolidated, often include larger dropstones.
Glaciomarine Deposits
aFine (clayey to sandy muds), well sorted, finely stratified (often varved – annual sandy summer layers alternating with clay winter beds), unconsolidated, often include larger dropstones but typically massive, more clay, marine fossils.
raised beach deposits
Like any beach, but usually well above modern sea level –gravelly layer at the top of the Dallas Road bluffs (just below the organic rich loess at the surface)
Climate oscillations
Ice ages
Most recent Ice age
Late Cenozoic
Most recent glacial stage
Wisconsinan
Laurentide Ice sheet
Covered most of Canada east of rockies
up to 3 kn thick
Cordilleran Ice sheet
Coalescent alpine glaciers in western mountains
flowed together as pedimont glaciers
Covered all of bc
Eustatic
Glaciation-> water stored in glaciers-> sealevel fall Vice versa
Measured in un glaciated (tropical) areas
Isostatic
Glaciation–> isostatic depression of crust into mantle–> sealevel rise
Measured in glaciated areas
