GEOL101: Glaciers

How do glaciers form?

From accumulation, compaction, and recrystallization of snow into ice over time.

Where are glaciers found today?

Polar regions (Antarctica, Greenland) and high mountains worldwide.

What is the common characteristic of where glaciers are found?

Cold climate or high elevation where snow persists year

About how much of Earth's surface is covered by glaciers today?

~10%.

In what direction does the ice flow when a glacier is advancing?

Forward, extending beyond its previous position.

In what direction does the ice flow when a glacier is retreating?

Ice still flows forward, but melting exceeds accumulation, so the terminus moves back.

In what direction does the ice flow when a glacier is neither advancing nor retreating?

Ice flows forward at the same rate as melting; terminus is stationary.

What landscape features are created by glaciers?

U

What do glacier

carved valleys look like?

What are glacial striations?

Scratches or grooves on bedrock caused by rocks embedded in moving ice.

Which type of glacial deposits are well sorted and which are poorly sorted?

Well

Glaciers

Thick ice masses, originate from snow, form on land, move slowly, part of hydrologic cycle, 10% of land surface, significant water reservoirs.

Types of glaciers

Valley (alpine), ice caps, ice sheets.

Valley glaciers

High altitudes, bounded by rock walls, flow down

Ice caps

Large dome

Ice sheets

Continent

Glacier formation

Snow accumulates faster than lost, compacts, recrystallizes into ice.

Terminus

Forward end of glacier; can advance, retreat, or remain stationary.

Most valley glaciers

Currently retreating; some advancing or stationary.

Glacier movement

Always flows forward, even if terminus retreats.

Erosion by glaciers

Effective erosion agents; carry huge blocks of material.

Entrainment

Erosion of sediment & large debris.

Plucking

Loosening & lifting fractured rock.

Abrasion

Scraping by ice & rock fragments.

Valley glacier landforms

Glacial valleys, hanging valleys, U

Ice sheet/cap landforms

Drumlins (elongated hills, sediment), Roche Moutonnee (streamlined bedrock hills).

Other erosion features

Glacial striations, grooves.

Glacial transport

By glacier & meltwater.

Glacial till

Deposited by glacier, poorly sorted, may show scratches; lateral, medial, end, ground moraines.

Stratified drift

Deposited by meltwater, well

Kettles

Depressions formed when ice block buried in sediment melts.