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AIM: Erosional and Depositional systems Do Now: In your notebooks… 1) Define the two terms below in your own words. 2) Explain how the two terms work together. Erosion: The movement/transport of material from one place to another Deposition: The dropping/placement/leaving behind of material AIM: How do Glaciers change the landscape? Do Now: The material seen below was left behind by a retreating glacier. Describe the sediments seen in the picture. Tasman Glacial Moraine, New Zealand I. Types of Glaciers Formed from the accumulation of ice and snow over thousands of years. • Valley Glacier: thick mass of ice that flows between mountains (in valleys). • Ice Sheets (continental ice): thin, flat layers of ice that flow in all directions covering the land and extends into the ocean. II. Glacial Movement - Glacial movement is called • Glaciers advance when they accumulate (gain) more ice. They also slide very slowly down hill •Glaciers retreat when pieces of ice fall off or melt. III. Glacial Features A. Erosion - Glaciers carve U-shaped valleys through the ground. - The Finger Lakes in Western NY were carved out by glaciers 2 MYA. • Plucking - when glaciers loosen and lift up rocks from the surface. • Striations - scratches and grooves in the bedrock caused by rocks trapped in the glacier. These rocks abrade against rocks on the surface as the glacier moves. B. Deposition - Glaciers create piles of till, which is unsorted sediment. • moraines are long ridges of till formed by the glacier. Terminal moraines are found at the head of the glacier after it retreats. - Melt waters coming from the glacier creates outwash plains in front of the glacier. **This melt water sorts and layers the sediments. • kettle lakes are formed from melting ice that was buried. Lake Ronkonkoma • Glacial Erratics are large boulders left behind from melting glaciers like those found in Central Park, NY. Central Park, NY • Drumlins are teardrop shaped hills of till. *The more narrow side points in the advancing direction of the glacier. The red lines show where the glaciers stopped advancing and deposited terminal moraines of unsorted material across the area that is now Long Island (25,000 years ago). These terminal moraines form the “backbone” upon which Long Island is built on. South of these moraines, glacial melt water created outwash plains where the unsorted piles were spread out into layers. Drumlins Closure • From the back bin, obtain a worksheet on Glaciers. With the person sitting next to you use the notes to answer the questions on the handout. How do Glaciers Change the Landscape? Worksheet 1. Ice Sheets • Thinner, flat expanse of ice •Covers continents and can extend out into oceans •Also called continental ice Glacial Valley •Creates “UShaped” trough •Moves between two mountains (steep rock) •Occurs only on continent 2. Both are cause erosion to occur. Plucking loosens and picks up rock from the surface of the Earth. Rocks trapped in the glacier abrade against rocks on the surface of the Earth creating striations. 3. It was created by a glacier because of the “U-shaped” valley that was created 4. Over the last 25,000 years glaciers have shaped the land in New York. Glaciers advance when they freeze more water than melts away. At two different times glacial advances plucked sediment out of the ground and moved it South. During glacial retreats, when more water melts than freezes, the sediment was left behind to form two moraines. These moraines later became the North and South shores of Long Island.