12 Glacial History Flashcards
Define Ablation
refers to melting, runoff, evaporation or sublimation of the ice, resulting in a thinning of the ice if it is not replenished by some other process.
Define sublimation
transformation from solid to gaseous state
How does glacial ice move and why is it like that?
The lower layer of a glacier moves plastically because of the pressure. Allowing glaciers to move like viscous fluid
What is the name of the cool period in the Precambrian?
Proterozoic Snowball Earth
What changes naturally on earth and what are the two kinds of periods?
Climate and periods of WARM and COOL have alternated over geologic time
What is the name of the cool period from Carboninoferous- Permian?
Late paleozoic Gondwana glaciation
What did the Late Paleozoic Gondwana glaciation form and what one place can you see that?
Carbonate cycles and can find this at the Johnston Canyon Formation
What is the cool period called from Tertiary- today?
Slide 28
Pleistocene glaciations
Define a glacial period
An interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier
advances.
Define an interglacial period
Period of warmer climate between glacial periods
Define a stadial period
A period of lower temperatures during an interglacial
* Like the Little Ice Age
What glacial period are we currently in and are we in a glacial or interglacial period?
We are currently living in the Holocene epoch, which is an interglacial.
What happened during the last Pleistocene glaciation?
Slide 33
The whole Canadian Cordillera was covered with a glacier
What time frame did the Cordilleran ice sheet deglaciate in the last Pleistocene glaciation?
16,500 - 5,700 years ago
When was the last glacial maximum for the Cordilleran ice sheet and what glacial period?
~20,000-30,000 years ago during the Wisconsin glacial
When was the start, peak and end of the Wisconsin glacial? And how much ice did it cover the Cordillera with?
Start; ~110,000 years
Peak: ~20,000-30,000 years
Ended: ~11,000 years
Covered the cordillera with 1-2 KM of ice
What period followed the Wisconsin Glacial and what time did it start?
Holocene interglacial began ~11,000 years ago
Little ice age
Slide 44
What are the two ways that glaciers form the landscape?
- Erosional features – sculpting of the mountains
- Glacial deposits – layers of sediment moved by glacial activity
What are 6 formations from glaciation?
- U-shape valley
- Hanging valley with waterfall
- Arete
- Horn
- Cirques
- Sharp mountain profiles
Describe glacial abrasion and striations.
Abrasion occurs when the ice and the load of rock
fragments slide over the bedrock and function as
sandpaper that smooths and polishes the surface
situated below.
What are the glacial dispositional features? (6)
1.Lateral moraine
2. Terminal moraine
3. Till
4. Outwash
5. Drumlin
6. Erratics
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Slides 84-88
