Definition A glacier is a thick mass of ice that forms over land from the compaction and recrystallization of snow and shows evidence of past or present flow
Valley/Alpine Glaciers • Ice masses that slowly advance down mountain valleys originally occupied by streams. • A stream of ice that flows between steep rock walls from near the top of the mountain valley.
Ice Sheets/Continental Glaciers • A stream of ice that flows between steep rock walls from near the top of the mountain valley. • Ice sheets are sometimes called continental ice sheets because they cover large regions where the climate is extremely cold. • They are huge compared to valley glaciers. • They currently cover Greenland and Antarctica.
Glacial Movement • Plastic flow involves movement within the ice • Basal slip slipping and sliding downward due to gravity
Glacial Budget The glacial budget is the balance, or lack of balance, between accumulation at the upper end of a glacier and loss, or wastage, at the lower end.
How Glaciers Erode • Plucking • lifting of rock blocks • Abrasion • Rock flour (pulverized rock) • Striations (grooves in the bedrock)
Glaciated Valleys A glacial trough is a U-shaped valley that was once V-shaped but was deepen by a glacier.
cirque a bowl-shaped depression at the head of a glacial valley.
Arêtes and Horns - Snaking, sharp-edged ridges and sharp pyramid-like peaks which project above mountain landscapes.
Glacial Deposits (Glacial drift) • Till is material deposited directly by the glacier. • Stratified drift is sediment laid down by glacial meltwater.
Moraines layers or ridges of till • Lateral • Medial • End • Terminal end • Recessional end • Ground
Outwash Plains sloping plains consisting of deposits from meltwater streams in front of the margin of an ice sheet
Kettles depressions created when a block of ice becomes lodged in glacial deposits and subsequently melts
Drumlins streamlined, asymmetrical hills composed of glacial dirt
Eskers ridges composed largely of sand and gravel deposited by a stream flowing beneath a glacier near its terminus
fjord a glacial valley that has been invaded by the sea. "Fjord" is a Norwegian word.
Effects of Glaciation • Erosional and depositional work • Animal and plant migration (which may lead to extinction of organisms that cannot tolerate such stresses) • Change in stream course • Sagging/Rebounding of land • Changes in sea level • Effects on the climate • Formation of pluvial lakes
The Milankovitch Theory MilutinMilankovitch One of the most significant theories relating Earth motions and long-term climate change. It is a mathematical theory of climate based on the seasonal and latitudinal variations of solar radiation received by the Earth. It states that as the Earth travels through space around the sun, cyclical variations in three elements of Earth-sun geometry combine to produce variations in the amount of solar energy that reaches Earth.
The Milankovitch Theory Cycle 1: Eccentricity • variations in the shape of the Earth’s orbit around the sun • Primary periodicities of 96,000 and 413,000 years • differences in solar radiation receipt of about 30% may occur between perihelion and aphelion.
The Milankovitch Theory Cycle 2: Obliquity • changes in the angle that Earth's axis makes with the plane of Earth's orbit • period of 41,000 years • tilt varies between 22 and 24.5 degrees
The Milankovitch Theory Cycle 3: Precession • the change in the direction of the Earth's axis of rotation • period of 22,000 years • most complex of the three orbital variation and is caused by the gravitational forces exerted on the Earth by all the other planetary body's in our solar system