Glacial Flashcards
When does glacial ice form? (What must be greater?)
When accumulation (snowfall) in winter is greater than ablation (melting) in summer
Accumulation > ablation
What are some possibilities in which glaciers can form?
Global cooling due to elliptical orbit of earth (every 97,000 years)
Earth’s axis tilts every 41,000 years (maximum tilt means north pole gets less sunlight, more accumulation)
Simultaneous volcanic eruptions could trigger an ice age
A large asteroid with the same catastrophic climatic result as volcanic activity
How do glaciers form?
If snow accumulates enough, the snowflakes become compact from the compression to become ice
Firn
The halfway stage between snow and solid glacial ice where periodic freezing and thawing creates a semisolid crystallized slush
Blue glacier
A glacier where the ice is so concentrated that it squeezes out all of the air to the point where it looks blue
What’s the difference between an alpine and a continental glacier?
Alpine/valley glaciers originate from the mountains and move down into lowland areas, while continental glaciers form on flat land and spread out.
Isostatic sinking
The enormous weight of ice sheets pushing the continent down (during the last ice age)
Isostatic rebound/readjustment
The rise of landmasses that were weighed down by ice sheets during the ice age (bounce back)
Will result in the drying of the Hudson Bay and the altering of drainage patterns
What are raised beaches and how are they formed?
Raised beaches are landforms that were originally beaches, but now lie above sea level. They form during Isostatic rebound, when the land rises after glacial ice melts
What is the difference between till and outwash?
Till is unsorted and unstratified glacial debris, meaning that it can consist of very large rocks and boulders.
Outwash is sorted and stratified glacial deposits and have a limit to the size of particles that it can carry
(Till = when glacial ice melts
Outwash = deposit left by running glacial meltwater)
Cirque
A hillside hollow formed by plucking and abrasion where glacial ice accumulates, deepening the depression
Tarn
When a cirque fills up with water after glaciation to form a small lake
Arete
A sharp ridge created by the action of two cirques eroding the mountain between them
Col
If erosion continues to wear down the wall of rock between two cirques, a mountain pass known as a col will form
Horn
The sharp peak formed when several cirque glaciers erode a mountain from more than two sides
Ex: the Matterhorn in the Swiss Alps and Mt. Assinaboine in the Rockies
Striations
Scrape marks left in the bedrock that are carved out by debris carried in the bottom of the glacier
Lateral moraine
Debris carried along and deposited at the side of a glacier as it melts
Medial moraine
As alpine/valley glaciers come together, lateral moraines join to become medial moraines > dark lines in the middle of the main valley glacier
Terminal moraine
The mound of debris left at the farthest point of glacial advance
Recessional moraine
As a glacier receded, ridges of debris are deposited. This occurs when melting is equal to the snowfall and the glacier remains stationary, depositing debris at its snout
Esker
When meltwater flows below the ice and emerge at the snout. The moving water carries debris with it, and over time the deposits are dropped off at the snout of the glacier. Eventually, a long snake-like deposit called an esker will take shape
Recess
When glaciers take breaks and leave behind mounts of dirt
Truncated spurs
Steep, often vertical valley walls created when a glacier moves through a river valley and shave off the sides
Hanging valleys
Small tributary streams that, before glaciation, flowed down the slopes to the main valley floor (tributary valleys were left hanging high along the side of the U-shaped valley)
Have waterfalls cascading down the steep walls
