Glaciers Flashcards
On Exam 2 (Apr. 1)
How is snow close to the equator possible?
Mountains (temp decreases with elevation)
Snowball Earth (global or near-global coverage of ice)
Where do glaciers form? How do they form?
On land NOT in water
From the compaction of snow
What are the two ways that glaciers can move?
Plastic Flow: pressure causes ice crystals to change shape (flatten), creating internal movement
Basal Sliding: a layer of meltwater between the glacier and the ground acts as a lubricant (without internal movement)
What two ways do glaciers erode rocks?
Abrasion: grinding and polishing of underlying rock by material carried in the glacier, which creates striations (scratches)
Plucking: loosening and removal of rock fragments (of any size) from the glacial bed
What geological evidence might there be for past glaciers? What types of rocks would we see?
Striations and gouges in rocks
Large conglomerates: poorly sorted, angular, and immature rocks
How are desert and glacial rocks different?
Desert: wind, small grains, well-sorted, rounding, cross-bedding, abrasions, undercutting, sandstone
Glacier: water/ice, large + small grains, poorly-sorted, abrasions, no rounding, conglomerates/breccias
What defines an ice age? Are we in one?
If there are ice sheets
Yes, because we have two (Greenland and Antarctica)
What would happen if the ice sheets melted?
Sea level rise would sink major cities
What is the snowball (albedo) effect?
Ice/snow reflects light and heat, making it colder, allowing more ice to freeze, leading to more reflection, and so on
This also works in the opposite direction (melting ice = hotter temps = less ice…)
How do ice ages happen on Earth?
Combination of:
- fluctuations in solar radiation (Milankovitch cycles)
- continents at the poles
- absence of greenhouse gases
How do plate tectonics influence ice ages? How did it influence Antarctica freezing over?
Plate tectonics = continents at the poles (land + cold temps is needed to form glaciers )
Antarctica split from South America, opening the Drake Passage. Cool currents began to circulate the continent, making it even colder
How do “flower pot rocks” form? (Think Bay of Fundy)
Glaciers melting = water soaking into cracks in the ground + re-freezing = widening of cracks and so on
This is a combination of physical and chemical weathering called freeze-thaw
