EARTH SCIENCE CHAPTER 15 GLACIERS. Chapter 15 GLACIERS I. What is a Glacier? Mass of moving ice responsible for the most powerful agents of erosion Types

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EARTH SCIENCE CHAPTER 15 GLACIERS Slide 2 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) Slide 3 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! Slide 4 SNOW LINE Topic 3The Snow line A. Definition Where permanent snow occurs. More is produced than melts B. Snowline versus latitude Lower at greater latitudes Slide 5 Slide 6 Slide 7 Slide 8 Slide 9 Slide 10 Slide 11 Slide 12 BIRTH Topic 4Birth 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 Slide 13 Slide 14 Slide 15 Slide 16 Slide 17 Slide 18 Slide 19 ALPINE GLACIERS Topic 5Where Valley Glaciers Occur (Alpine Glaciers) A. Locations Where mountains have elevations above snow line. Slide 20 Slide 21 Slide 22 Slide 23 Slide 24 CONTINENTAL GLACIERS Topic 6Where 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 Slide 25 Slide 26 Slide 27 Slide 28 MOVEMENT II. Glacier Movement Topic 7How 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. Slide 29 CREVASSES Slide 30 Slide 31 HOW FAR? Topic 8How 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 Slide 32 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 hasnt broken off yet Slide 33 Slide 34 Slide 35 Slide 36 Slide 37 Slide 38 Slide 39 TRANSPORT Topic 9Glaciers Transport Loose Rock A. Range of particle size Fine powder to giant boulders Slide 40 MORAINES 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 Slide 41 Slide 42 Slide 43 Slide 44 Slide 45 EROSION Topic 10Glaciers 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. Arte - knife edge ridge between 2 cirques 5. Horns - result of 3 or more cirque producing a pyramid shaped peak Slide 46 STRIATIONS Slide 47 Slide 48 HORN Slide 49 Slide 50 CIRQUE Slide 51 Slide 52 ARETE Slide 53 Slide 54 Slide 55 GLACIAL VALLEY Topic 11 Recognizing Glacial Valleys A. Glacial troughs versus river valleys 1. U shaped vs. V shaped B. Hanging troughs and hanging trough waterfalls SMALL ABANDONED GLACIAL VALLEY SUSPENDED ON A MOUNTAIN ABOVE THE MAIN GLACIAL VALLEY. WHAT NATURAL FEATURE DO YOU THINK WILL APPEAR WHEN A STREAM FLOWS FROM A HANGING VALLEY TO THE MAIN GLACIAL VALLEY? Slide 56 Slide 57 Slide 58 Slide 59 Slide 60 Topic 12 What Continental Glaciers Do A. Polished mountain tops versus sharpened ones Slide 61 Slide 62 DEPOSITION III. Deposits By Glaciers Topic 13 Deposition Occurs Drift - all deposits of glaciers 1. Till - unsorted and unstratified (inside glacier) 2. Outwash - sorted and stratified (left in front of glacier) Slide 63 TILL Slide 64 Slide 65 Slide 66 Slide 67 OUTWASH PLAIN Slide 68 Slide 69 Slide 70 DEPOSITION Topic 14 Glaciers Leave Moraines A. Recessional and terminal moraines - whats left behind by a glacier and the deposit left by farthest advance. B. Erratics - large transported boulders Slide 71 MORAINES Slide 72 MORAINE Slide 73 Slide 74 ERRATIC Slide 75 ERRATICS Slide 76 DRUMLINS Topic 15 Drumlins A. Formation and description - long smooth canoe - shaped hills made of till produced when advancing glaciers have run over earlier glacial moraines B. Examples - Southeastern Wisconsin, South of Lake Ontario, Boston, Massachusetts Slide 77 DRUMLINS Slide 78 Slide 79 Topic 16 Outwash Plains and Eskers A. Outwash plains Formation and description - broad flat areas in front of glaciers (usually prairies or farmland today) B. Eskers Formation and description - long winding ridges where material was deposited in tunnels within glacier Examples - Maine and New York Slide 80 OUTWASH PLAIN Slide 81 Slide 82 ESKER Slide 83 Slide 84 Slide 85 Topic 17 Kames, Kettles, and Deltas A. Kames 1. Formation and description Small cone shaped hills of sand and gravel from streams on top of glaciers B. Kettles 1. Formation and description Circular hollows on terminal moraines and outwash plains formed from large blocks of ice settling out and melting C. Deltas 1. Formation and description When glacial streams empty into lakes Slide 86 KAMES Slide 87 OUTWASH PLAIN Slide 88 Slide 89 CIRQUE LAKES Topic 18 Lakes Made by Glaciers A. Cirque lakes 1. Formation When water fills the rock-floored cirque left by a glacier 2. Examples Lake Louise, British Columbia Slide 90 CIRQUE LAKE Slide 91 KETTLE LAKES B. Kettle lakes 1. Formation Water from ice melt left behind in kettles 2. Examples Zillions of them in Minnesota and Wisconsin, not to mention the Great Lakes Slide 92 Slide 93 Slide 94 C. Moraine dammed lakes 1. Formation River valleys blocked by glacial moraines 2. Example Devils Lake, Wisconsin Slide 95 Slide 96 Slide 97 Slide 98 Slide 99 Slide 100 ICE AGE IV. The Ice Age (NOTE OBJECTIVES A C ON PAGE 183) Topic 19 How It Happened A. When it occurred - 1,000,000 years ago, were still in it! B. Extent - Intersection of Ohio and Mississippi rivers and as far east as NY C. North Americas 3 major centers 1. Labrador center - east 2. Keewatin - central 3. Cordilleran - west D. Cyclical - Advanced and receded 4xs; 11,000 years ago was last advance Slide 101 Slide 102 Topic 20 Ice Age Evidence A. Limits tied to terminal moraines Terminal moraines found from New Jersey through Pennsylvania, to Indiana and beyond. Outwash plains are found beyond. Slide 103 Slide 104 Topic 21 Causes of Glacial Climates A. Four facts to consider 1. I million years ago, Ice Age began, including 4 major advances of the ice sheets. 2. Warm interglacial periods came between. 3. Other ice ages have occurred in the past 600 million years. 4. In last age, glaciers advanced and receded in North and South hemispheres at the same time. Slide 105 B. Possible causes 1. Energy from sun changes. 2. Volcanic activity and dust in atmosphere. 3. During mountain building more land was above snow line. (More land under ice, might change the climate) 4. Continents in older formations may have prevented hot and cold water currents from mixing. 5. Changes in earths tilt. Slide 106 Slide 107 Slide 108 Slide 109