EARTH SCIENCE CHAPTER 15 GLACIERS
GLACIERS • Chapter 15 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)
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 60 METERS!
SNOW LINE • Topic 3 The Snow line • A.Definition • Where permanent snow occurs. More is produced than melts • B.Snowline versus latitude • Lower at greater latitudes
BIRTH • Topic 4 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 • Topic 6 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 • D.Nunnataks • Mountain peaks that project through ice
MOVEMENT • II.Glacier Movement • Topic 7 How Glaciers Move • A.Process of movement • 1. Weight pulls ice down • 2. Melting aids lubrication • B.Speed • 1.Movement • From a few cm to 3000 cm /day • Faster in the middle.
HOW FAR? • Topic 8 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
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
TRANSPORT • Topic 9 Glaciers Transport Loose Rock • A.Range of particle size • Fine powder to giant boulders
B.Moraines - deposited particles once glacier recedes 1.Ground moraines - in glacier before deposited 2.Lateral moraines - deposited on sides of glaciers 3.Medial moraines -deposited on the sides of two converging glaciers, resulting between the two 4.End moraines - deposited at the ice front MORAINES
EROSION • Topic 10 Glaciers Leave Their Mark • A.Description and formation • 1.Striations - long parallel scratches • 2.Roches moutonnees - sheep rocks • 3.Cirque - semicircular basins at head of valley • 4.Arête - knife edge ridge between 2 cirques • 5.Horns - result of 3 or more cirque producing a pyramid shaped peak