What is a glacier? 0 A large, long-lasting mass of ice which forms on land and moves downslope because of gravity. What metaphors do we use for glaciers? 0 Glaciers are often referred to as a River of Ice or 0 Bulldozer of Ice How do glaciers form? http://library.thinkquest.org/3876/images/howgla.gif How do glaciers form? Glaciers form over many years in places where the snowfall in winter exceeds the snow melt in summer Gravity pulls the ice down the hill http://www.swisseduc.ch/glaciers/earth_icy_planet/icons-11/20.jpg What are the two types of glaciers? Alpine and Continental Alpine Glaciers 0 A.k.a. Valley Glaciers 0 form near mountain tops and slide down the valleys 0 They can be hundreds of feet thick. Tyndall Glacier, Alaska Aletsch Glacier, Switzerland 115 sq miles http://travelguide.all-about-switzerland.info/pictures-famous-swiss-glaciers.html Continental Glaciers Continental Glaciers 0 cover large areas (Antarctica, Canada) 0 can be 2 – 3 miles thick 0 Weight of the ice depresses the ground 0 When these glaciers melt the land ‘rebounds’ 0 Some areas depressed during the last ice age are still rising http://www.prolitegear.com/prolitegear/images/large/antarctica_02_lg.jpg http://exposedplanet.com/images/antarctica-group-sled-vinsonbc-camp1.jpg http://exposedplanet.com/images/mountain-rangefrom-ph-antarctica.jpg What are the Landscape Features of Glaciated Areas? What are the landscape features left by Alpine or mountain glaciers? 0 Till- direct deposit of glacier; unsorted sediment 0 Mountain shape: 0 Rugged landscapes 0 Jagged peaks 0 U-shaped valley 0 Moraine- a mass of till Rugged Landscapes Jagged Peaks Northeast-looking oblique aerial photograph showing the snow-covered summit accumulation area of Mount Fairweather, Fairweather Range, Glacier Bay National Park, Alaska. Materhorn http://www.kuleuven.ac.be/geologie/geo-algemeen.html West-looking photograph showing an angular arete ridge, composed of schist, on the upper Taku Glacier, Juneau Icefield, Tongass National Forest, Coast Mountains, Alaska. U-Shaped Valley River Valley Glacial Valley http://www.nps.gov/history/history/online_books/brochures/1936/glac/ima ges/fig13c.jpg Moraine 0 Mass of till (unsorted sediment) left by a glacier http://www.yosemite.ca.us/library/geologic_story_of_yosemite/images/62.jpg The u-shaped valley to the right side of the photo is the ice-free valley of Talkeetna Glacier, Talkeetna Mountains, Alaska. Note cirque at the top of the valley on the left. Aletsch Glacier, Switzerland http://travelguide.all-about-switzerland.info/pictures-famous-swiss-glaciers.html Ground Moraine Terminal Moraine Mendenhall Glacier, Tongas National Park What are the characteristics left by Continental Glaciers? 0 Valleys- u shaped 0 Till - unsorted sediment 0 Kettle lakes 0 Scratches and grooves 0 Drumlins Kettle Lake http://www.scienceclarified.com/images/uesc_06_img0334.jpg http://dnr.metrokc.gov/wlr/waterres/smlakes/LakeStewWeb25/GeoDrawing.JPG Finger Lakes 0 streams and lakes were modified by glaciers 0 Retreating glaciers deposited recessional moraines that blocked the water flow and created deep lakes 0 Examples 0 Seneca lake: 40 miles long, 618 feet deep 0 Cayuga: 40 miles long, 435 feet deep http://upload.wikimedia.org/wikipedia/commons/5/5f/Fingerlakesmap.png NASA photo Striations (Scratches) http://images.google.com/imgres?imgurl=http://education.usgs.gov/schoolyard/IMAGES/GlacialStriations2.jpg&imgrefurl=http://educatio n.usgs.gov/schoolyard/CoolGeologyActivity.html&h=297&w=447&sz=45&hl=en&start=1&tbnid=y1qmEFaxgJ64ZM:&tbnh=84&tbnw=12 7&prev=/images%3Fq%3Dglacial%2Bstriations%26gbv%3D2%26svnum%3D10%26hl%3Den Grooves Polished Rock http://3dparks.wr.usgs.gov/nyc/images/fig21.jpg Drumlin http://oz.plymouth.edu/~sci_ed/Turski/Courses/Earth_Science/Images/4.drumlin.jpg http://geoscape.nrcan.gc.ca/calgary/geotour/6_e.php A SWARM OF DRUMLINS http://www.drumlinarealandtrust.org/images/drumlins.jpg Icebergs Form when chunks of ice ‘calve’ off the front of the glacier and land in the water http://images.google.com/imgres?imgurl=http://www.atacamaphoto.com/antarctica/antarctica22.jpg&imgrefurl=http://www.atacamaphoto.com/antarctica/antarctica22.htm&h=408&w=608&s z=101&hl=en&start=37&tbnid=raJxaBCeP2TyMM:&tbnh=91&tbnw=136&prev=/images%3Fq%3Dantarctica%26start%3D20%26gbv%3D2%26ndsp%3D20%26hl%3Den%26sa%3DN Iceberg in Antarctica Floating Icebergs A Zodiak is cruising along a glacier front, showing the tremendous size of the ice blocks Giant Iceberg Gentoo penguin family, Antarctica What are the tell-tale signs that a glacier was in the area? 0________________ valley 0________________ sediment 0________________ in bedrock See you in class!