Snow line – where snow remains year round. Formation of Glacial Ice from Snow.

Snow line – where snow remains year round

Formation of Glacial Ice from Snow

Forming Glacial Ice

Initial Form

2 weeks

7 weeks

8 weeks

Snow Firn Glacial Ice

Glacier movement

• When glacier reaches critical mass (> 20m thick), flow occurs

Types of Glaciers

slip

Plasticdeformation

Ice Deformation with Slip

What happens as ice melts

• Ice melt flows down to bedrock through crevasses and moulins (large tunnels)

• Water between bedrock and ice sheet acts as lubricant

• Allows ice sheet to move faster toward the coastline

• Ice movement-rate increases from~30 cm per day in winter to ~40 cm per day in the summer

Terminus

Advance & Retreat: Moraines

Alpine Moraines and Till

Moraine Types

Anatomy of a Glacier

Piedmont glacier

Types of Glaciers – Piedmont & Tidewater Piedmont: Originally confined alpine, spread at foot of mountains

Calving

Different kinds of glaciers

Ice extent Last Glacial Maximum (21,000 yr BP)

Retreat of North American (Laurentide) ice sheet

Different kinds of glaciers

Ice cap and continental (ice sheet)

Sentinal Range, Antarctica

Ice cap (Vatnakjokull in Iceland)feeds “outlet glaciers”

Greenland Ice Sheet

Greenland