Lecture 16: Cryosphere Part 2 Flashcards
-How Glaciers Form and Move -How Glaciers Form Different Landforms and Deposits -Importance of Glaciers
How does snow transform into ice?
Some snow survives the summer melt and is buried by successive snowfall.
- Then summer melting creates granular ice: Neve
- Pressure of the overlying snow starts to compact “snow” that survives one or more full seasons of melt (ablation): Firn
- Further compaction eventually forms ice
How are glaciers able to flow and where is flow the fastest?
Because ice crystals deform under stress.
-Flow fastest in centre and slowest at edges
What are the two classes of glaciers?
- Warm-based ice
2. Cold-based ice
What is warm-based ice glaciers?
Is close to the freezing point and has liquid water
What is cold-based ice glaciers?
Is below the freezing point throughout
What is accumulation?
Addition of mass to a glacier
What is ablation?
Removal of mass from a glacier
What is the equilibrium line?
The boundary between the accumulation and ablation zones, where net ablation = net accumulation
What is mass balance?
The difference between the amount of material that a glacier accumulates and the amount lost during ablation.
What causes striations and/or chatter marks?
Debris frozen into the base of the ice that is dragged along the surface, gouging it, as the glacier moves.
How are u-shaped valleys formed?
Gouged out by main trunk glacier
How are hanging valleys formed?
Tributary valley well above main valley floor carved by tributary glaciers
What are cirques?
Bowl-shaped valley formed at glacier head
What are aretes?
Sharp-edged ridges
What are horns?
Pointed pyramidal peaks
What are (pro)glacial lakes?
Lakes that form in front or along the margins of a glacier.
What is an outwash?
Gravel and sand deposits, deposited by meltwater beyond the terminus of a glacier
What is a till?
Unsorted sediments deposited by a glacier
What are five forms of moraines?
- End moraines: form at the terminus of a glacier
- Terminal moraines: marks the glaciers furthest advancement
- Recessional moraines: marking the retreat of the glacier
- Lateral moraines: form along the sides of the glacier
- Medial moraines: form when two glaciers join, merging their lateral moraines
What are drumlins and eskers and how do they form?
Drumlins: form when ice sheets mold subglacial sediments creating tear-dropped hills
Eskers: rivers flowing beneath the ice that leaves ridges of well-sorted sand and gravel
What are kames and how do they form?
A hill/hummock or terrace composed of stratified sand and gravel laid down by glacial meltwater.
What are kettles and how do they form?
A depression/lake formed in locations of large ice blocks calved from receding glaciers
What are moraines?
Accumulations of till
What are some reasons glaciers are important?
- Its ice holds records of past environments
- Can help us understand the relationship between temperature, greenhouse gasses, solar radiation, and changing climate
