2GLACIERS Chapter 15 GLACIERS I. What is a Glacier? Types of Glaciers Mass of moving ice responsible for the most powerful agents of erosion Types of Glaciers Valley (alpine)Continental (Greenland, Antarctica)
3TYPES 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 directionsLarger 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 DEEPFACT: IF GREENLAND AND ANTARCTICA ICE SHEETS WHERE TO MELT THE SEA LEVEL WOULD RISE TO 60 METERS!
4SNOW LINE Topic 3 The Snow line A. Definition Where permanent snow occurs. More is produced than meltsB. Snowline versus latitudeLower at greater latitudes
24CONTINENTAL GLACIERSTopic 6 Where Ice Sheets (Continental Glaciers) OccurA. LocationWhere snow line is close to sea levelB. Ice capsSmall ones (Iceland and Islands in Arctic Ocean)C. Continental glaciersAntarctic glacier (5 km thick and 1.5 m below sea level)GreenlandD. NunnataksMountain peaks that project through ice
28MOVEMENT II. Glacier Movement Topic 7 How Glaciers Move A. Process of movement1. Weight pulls ice down2. Melting aids lubricationB. Speed 1. MovementFrom a few cm to 3000 cm /dayFaster in the middle.
39TRANSPORT Topic 9 Glaciers Transport Loose Rock A. Range of particle sizeFine powder to giant boulders
40MORAINES B. Moraines - deposited particles once glacier recedes 1. Ground moraines - in glacier before deposited 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
45EROSION 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 cirques 5. Horns - result of 3 or more cirque producing a pyramid shaped peak
55GLACIAL VALLEY Topic 11 Recognizing Glacial Valleys A. Glacial troughs versus river valleys1. U shaped vs. V shapedB. Hanging troughs and hanging trough waterfallsSMALL 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?
62DEPOSITION III. Deposits By Glaciers Topic 13 Deposition Occurs Drift - all deposits of glaciers1. Till - unsorted and unstratified (inside glacier)2. Outwash - sorted and stratified (left in front of glacier)
76DRUMLINS Topic 15 Drumlins A. Formation and description - long smooth canoe - shaped hills made of till produced when advancing glaciers have run over earlier glacial morainesB. Examples - Southeastern Wisconsin, South of Lake Ontario, Boston, Massachusetts
79Topic 16 Outwash Plains and Eskers A. Outwash plainsFormation and description - broad flat areas in front of glaciers (usually prairies or farmland today)B. EskersFormation and description - long winding ridges where material was deposited in tunnels within glacierExamples - Maine and New York
85Topic 17 Kames, Kettles, and Deltas A. Kames1. Formation and descriptionSmall cone shaped hills of sand and gravel from streams on top of glaciersB. KettlesCircular hollows on terminal moraines and outwash plains formed from large blocks of ice settling out and meltingC. DeltasWhen glacial streams empty into lakes
100ICE AGE IV. The Ice Age Topic 19 How It Happened (NOTE OBJECTIVES A – C ON PAGE 183)Topic 19 How It HappenedA. When it occurred - 1,000,000 years ago, we’re still in it!B. Extent - Intersection of Ohio and Mississippi rivers and as far east as NYC. North America’s 3 major centers1. Labrador center - east2. Keewatin - central3. Cordilleran - westD. Cyclical - Advanced and receded 4x’s; 11,000 years ago was last advance
104Topic 21 Causes of Glacial Climates A. Four facts to consider1. 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.
105B. 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 earth’s tilt.