Glaciers

Alpine or Valley Glacier

A glacier confined to a valley

Arete

ridge created by two cirques

Calving

process of glacial ice breaking off into a body of water

Cirque

steep sided, half bowl shaped recess at the head of the glacier

Col

A saddle shaped arete

Crevasse

A crack in a glacier created by uneven movement

Drumlin

a long ramp shaped mound of till that is smoothed in the direction of the glacier's flow

Erratic

a large boulder moved and dropped by a glacier

Esker

long ridge of material deposited by a meltwater stream flowing beneath a glacier

Fjord

flooded glacial valley

Hanging Valley

A valley left by a melted tributary glacier that enters a larger glacial valley above its base, high up on the valley wall.

Horn

a pyramid shaped peak created by three or more cirques

Ice Cap

a dome shaped mass of ice that covers less than 50,000 square miles

Ice Shelf

A thick, floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface.

Kettle Pond

a kettle that is filled with water

Lateral Moraine

moraine that forms along the side of a glacier

Medial Moraine

A moraine formed when two advancing valley glaciers come together to form a single ice stream, forms in the middle of the glacier

Moulins

A cylindrical, vertical shaft that extends through a glacier and is carved by meltwater from the glacier's surface.

Outwash Plains

The area ahead of a glacier where all of the glacial rivers alluvial fans combine.

Snow line

The elevation above which snow remains all year long

Striations

Scratches left on rocks and bedrock by glacier movement

Glacial Valley or Trough

U-shaped valley formed by the erosion of the glacier

End Moraine

The edge of the glacier marking its maximum advance

Kettle

A small depression that forms when a chunk of ice is left in sediment and then melts

Glacial flour/ Rock Flour

Smallest size of sediment that is responsible for the milky, colored water in the rivers, streams, and lakes that are fed by glaciers.

Till

Sediment deposited by a glacier

Snow Line

The elevation above which snow remains all year long

Abrasion

The wearing away of rock material by grinding action of rock on rock.

axial precession (wobble)

The direction Earth's axis of rotation is pointed

Obliquity

The angle Earth's axis is tilted with respect to Earth's orbital plane

eccentricity

The shape of Earth's orbit

continental glacier

Dome shaped glacier of at least 50,000 square miles

drop stone

fragments of rock that have dropped from an overlying floating ice sheet and that have sunk into and depressed the layers beneath them.

Firn

partially compacted granular snow that is the intermediate stage between snow and glacial ice.

frost wedging

the mechanical disintegration, splitting or break-up of rock by the pressure of water freezing in cracks, crevices, pores, joints or bedding planes

glacial advance

when a mountain glacier's terminus extends farther down valley than before. usually associated with glacial periods (ice ages).

glacial retreat

a glacier that loses more water than it gains. usually associated with interglacial periods (warm periods).

glacier

A large, dense body of ice that is constantly moving due to its own weight

Ice Age

A period of time lasting tens of thousands of years, where Earth's temperature drops very low and the polar ice caps and glaciers grow toward the equator.

Ice raft

The transportation of rocks and sediments of any size, by icebergs, ice flows, or any other form of floating ice.

glacial period (ice age)

times with large ice sheets

interglacial period

times without large ice sheets

Louis Agassiz

the father of glaciology

Milankovitch cycles

changes in Earth's position relative to the Sun that are believed to be a strong driver of Earth's long-term climate, and are responsible for triggering the beginning and end of glaciation periods (Ice Ages).

Moraine

Mound, ridge, or other distinct accumulation of glacial till, usually pushed by the glacier.

recessional moraine

when a glacier has begun to recede, but then moves forward again, without ever reaching its farthest point.

terminal moraine

marks the farthest forward progression of

the glacier.

rigid zone

the upper brittle zone (top 130 ft) of a glacier where the ice cracks into crevasses

zone of plastic flow

the lower section (deeper than 130 ft) of a glacier that behaves like a plastic

zone of accumulation

the part of a glacier that receives more mass by accumulation than loses by melting (above the snow line)

zone of wastage

The area on a glacier where there is a net loss of snow and ice (below the snow line)