EARTH SCIENCE CHAPTER 17 GLACIERS
GLACIERS • Chapter 17 GLACIERS • I. What is a Glacier? • Mass of moving ice responsible for the most powerful agents of erosion • Types of Glaciers • Valley (alpine) Continental (Greenland, Antarctica) (Ice sheet)
TYPES OF GLACIERS • B. Valley glaciers (Alpine glaciers) • Long, slow moving stream of ice originating in the mountains. • C.Ice sheets (Continental Glaciers) • Originating at the poles and expanding in all directions • Larger than valley or alpine glaciers. FACT: ANTARCTICA HAS THE LARGEST CONTINENTAL ICE SHEET IN THE WORLD, 1 AND A HALF TIMES THE SIZE OF THE U.S. AND IN SOME PLACES 4,000 METERS DEEP FACT: IF GREENLAND AND ANTARCTICA ICE SHEETS WHERE TO MELT THE SEA LEVEL WOULD RISE TO 80 METERS!
SNOW LINE • The Snow line • A.Definition • Where permanent snow occurs. More is produced than melts • B.Snowline versus latitude • Lower at greater latitudes
BIRTH • Birth of a Glacier • A.Process • 1.Firn (see Fig 11-4 on p. 174) • Recrystalization of snow into rough grains • 2. Snow to Firn to Glacial Ice
ALPINE GLACIERS • Topic 5 Where Valley Glaciers Occur (Alpine Glaciers) • A.Locations • Where mountains have elevations above snow line.
CONTINENTAL GLACIERS • Where Ice Sheets (Continental Glaciers) Occur • A.Location • Where snow line is close to sea level • B.Ice caps • Small ones (Iceland and Islands in Arctic Ocean) • C.Continental glaciers • Antarctic glacier (5 km thick and 1.5 m below sea level) • Greenland
MOVEMENT • II.Glacier Movement • Topic 7 How Glaciers Move • A.Process of movement • 1. Gravity • 2. Pressure (Peer) • B.Speed • 1.Movement • From a few cm to 3000 cm /day • Faster in the middle.
Movement • Basal Slip • Internal Plastic Flow
HOW FAR? • How Far Glaciers Move • A.Ice fronts - Where they end (can be below snow line) • 1.Factors determining • Where ice melts as fast as it moves
CREVASSES Crevasses: Large Cracks in the glacier Can be up to 60 meters deep
CALVING • B.Calving • 1.Process • When glaciers hit sea, blocks break off • 2.Icebergs • What you get • 3.Ice shelves • Occur over water where ice hasn’t broken off yet
EROSIONAL FEATURES 1.Striations 2. Hanging Valleys 3.Cirque 4.Arête 5.Horns 6. Glacial Trough
Glacial Erosion • Striations- marks in bedrock due to the grinding of sediment under the glacier.
Cirque • Semi-circular (bowl shaped) basins at beginning of valley • Beginning of a glacier
HORN • Pyramid like peak resulting from several ajoining aretes and cirques
Arete • A sharp jagged ridge that forms between cirques
Glacial Trough • U shaped valley carved out by a glacier