Transcript glaciers
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: - Flow between mountains (in valleys) - Very thick • Ice Sheets (continental ice): - thin flat sheet of ice - expand in all directions covering the land II. Glacial Movement - Glacial movement is called • Glaciers advance when they accumulate (gain) more ice or slide very slowly down hill •Glaciers retreat when pieces of ice fall off or melt. III. Glacier Erosional Features • U-shaped valleys are carved in the landscape as glaciers move through the land The Finger Lakes in Western NY fill Ushaped valleys carved out by glaciers 2 MYA. • Glaciers pick up rocks in process known as plucking. • Striations – plucked rocks trapped in glacial ice abrade against rocks on the surface to form these scratches. IV. Glacier Depositional Features • create unsorted piles of till (mixed sediments). • moraines are long ridges of till formed by the glacier. • Terminal moraines are found at the end of the glacier. • Outwash plains are created by melt water coming from the glacier. - this melt water sorts the different sizes of sediments. • kettle lakes are formed from melting ice that was buried. Lake Ronkonkoma • Glacial Erratics are large boulders left behind from melting glaciers. Central Park, NY • Drumlins are teardrop shaped hills of till. - The narrow side of the hill points in the direction glacier was moving (advancing). Glacier moved this way in the past Narrow side of hill V. Glaciers and Long Island - Glaciers advanced from the North (from Canada) to the South (30,000 and 20,000 years ago) - As they moved they plucked and eroded rocks and soil creating piles of till and moraines. - When they retreated, this material deposited to form Long Island. 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 Glacial Valley • Thinner, flat expanse of ice •Creates “U-Shaped” trough •Covers continents and can extend out into oceans •Moves between two mountains (steep rock) •Also called continental ice •Very thick 2. Both cause erosion to occur. Plucking loosens and picks up rock from the surface of the Earth. Abrasion is caused when rocks trapped in the glacier grind against rocks on the surface of Earth. 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.