worksheet 8 Flashcards
when did the polar ice caps appear in south pole
40-45 mya in middle-late eocene (part of the paleogene)
when did ice caps appear in the north pole
beginning of quaternary period, ~2.5 mya
what is the name of the ice sheet in the south
antarctic ice sheet
what is the name of the ice sheet in the north
northern ice sheet
what could have caused the present ice house we are in
co2 being taken out of atmosphere by the uplift and erosion occuring when himalayas were formed (india and eurasian plate colliding)
what is necessary for ice sheets to form at the poles
continental landmasses
what causes advances and retreats of ice caps throughout the quaternary period
variation in surface temps
are we in a glacial or interglacial period
interglacial
is sea level higher in glacial or interglacial periods
interglacial bc water is not in ice sheetsw
what is the difference in sea level between glacial and interglacial periods
~100 m higher in interglacial
what causes glacial-interglacial cycles
glacial periods become interglacial periods when northern hemisphere’s summer solar insolation increased
eccentricity which also has periodicity of 100,000 years also has effect. as eccentricity increases, orbit is more egg shaped.
when was the most recent glacial cycle (aka ice age)
10,000-37,0000 years ago
what is EISC and how big was it
eurasian ice sheet complex
about 4500 km
how did the EISC change throughout time
3 distinct nucleation points (UK/Ireland, barents sea, scandinavia) which is grew and collapsed from
what was the effect of EISC on shorelines
shorelines advanced as sea level fell so it varied throughout the ice age
what geomorphological features formed by glacial erosion are still in ireland
- u-shaped valleys
- nunataks
- roches moutonnees
what is a u shaped valley
formed by glacial erosion
v-shaped river valleys were eroded to form u-shaped glacial valleys
what are nunataks
formed by glacial erosion
“glacial islands” at tops of ridges, mountains or peaks that were not covered with ice or snow either at edge of ice sheet or within it (poked out the top of glaciers)
what are roches mountonnees
formed by glacial erosion
bumps or hills of bedrock that are asymmetric with short steep lee side and long gentle sloping stoss side that show glacial movement (saw in killiney)
what geomorphological features and deposits formed by deposition beneath or at the margins of ice sheets are common in ireland
- moraines
- esker
- drumlins
whats a moraine
accumulation of debris formed at margin of glacier
whats an esker
subglacial stream deposits that form sinuous elongate (long curvy) ridges of sand and gravel
whats a drumlin
long ridge formed by ice moving over unconsolidated sediments (similar to roches by made of till)
what geomorphological features are associated with post glacial periods like the holocene
- rias or fjords
- drowned drumlins
whats a fjord/rias
drowned valleys that were covered when the sea level rose
what was the inferred pattern of ice flow of the ice sheet that covered Ireland/Britain (BRITICE)
flowed from high -> low ground
when was the BRITICE at max southern
23,000 years ago
what topography does the maximum extent of BRITICE align with
the present day shelf in the ocean as it restricted any more movement (water was too deep to ground any futher)
what geomorphic feature found offshore in the atlantic were used to infer the western limits of the ice sheet
moraines on the current continental shelf
what are trough mouth fans and where are they found
fan/delta accumulations of sediment that develops at the end of glacier troughs on the end of continental shelves
form bc sediment is fed to the slope which ends and the sediment accumulates in fan shape
what are erratics and what are they formed of
large boulders transported by ice sheets
formed by hard igneous rock because if it is weaker than it will be ground up
