GEOG 2OC3 Lecture Notes - Lecture 2: Iron Age, Arctic Circle, Gneiss
26 May 2018
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THE ICE AGE/ GLACURES
Quaternary period: Recent glacial episodes that began about 2.5 million years ago
• Humanoid species began to evolve into anatomically modern forms and migrated around the
world
• Most recent glacial episode ion the north hemisphere with ice sheets covering to 30 degrees US
• Global plate distribution has stabilized, ice sheets covering parts of Canada and Europe
Orbital Controls on Glaciation
• Earth orbits the sun in an ellipse
• Certain departures from this general shape due to the gravitational pull of the Sun and Moon on
the Eath’s euato, Orbital eccentricity, axial progression, cause solar insulation
Orbital Eccentricity: The depatue fo the eath’s elliptial oit fo a iula shape, ifluees o
solstices and equinox
Axial Precision: The slo otiuous hage i the eath’s otatioal ais aused the gaitatioal
pull on Earth by the sun and moon (which is why it wobbles slowly)
Axial Tilt: Angle of the tilt between the earths rotational axis and orbital axis, the reason we have
seasons (tilt: 23.5)
Glacial Cycles
• Insolation jobs -> sea gathers at poles -> glaciers advance, scour landscape -> sea level lowers,
atmosphere becomes drier -> insolation rises -> glaciers retreat -> sea level rises atmosphere
becomes warmer and wetter
• As global temperatures drop, this formed glaciers over many years. As they grow they take
larger volumes of water, reducing sea levels
• As glaciers grow, they sit by many layers of rock leaving deep lines of bedrock (creating many
lakes found in Canada)
• As the glaciers retreat and melt, this water contributes to rising sea levels
Glacial Landforms
Result from various processes
1. Erosion by ice/meltwater
2. Deposition by ice/meltwater
Drumlins: Elongated hill in the shape of an inverted spoon formed by the advance of a glacier acting
on the underlying unconsolidated material
Southern Ontario
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Moraines: Ridges or mounds of glacial material deposited close to the ice margin, often associated with
uneven topography- looks like ice rivers down mountains
Eskers: Winding ridges of stratified sand and gravel frequently kilometers long, possibly formed from
meltwater running through glacial tunnels
The Great Lakes
• Retreat of the glaciers around 100,000 years ago created depressions in the landscape that were
then filled with water
• % of the old’s fesh ate
The Canadian Shield
• Originally a mountain chain, it has since been worn down by erosional processes
• The retreat of glaciers across the roots of the mountains scraped off rock underlayers to expose
the underlying bedrock
Erratics/Drop stones: Deposited by retreating glacial ice, often rocks geographically and geologically
unrelated to their situation
Muskeg: swamp or bog consisting of a mixture of water and partly dead vegetation, frequently covered
by a layer of sphagnum or other mosses
Perma frost: Subsurface material that has remained in a frozen state for 2+ years
• Most of Canada is either continuous (always frozen) or discontinuous (frozen for part of the
year)
Solar insolation: The amount of solar radiation that the earth receives over a surface area at a specific
time
PALEOGRAPHY
Circumstances defining a favorite physical base can change over time and such changes have the power
to alter the prospect for regional expansion and contraction
Hadean period: earth was just lava
Canadian shield: a remnant from the early volatile volcanic days on Earth, and contains some of the
Earths oldest igneous rocks
Mountain belts (oregonites): built from forced called convergent stress and strain
• Two tectonic plates squeeze together, rock is piled up in the middle to form mountains (how
the rocky mountains were made)
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find more resources at oneclass.com
