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Erosion & Deposition by Ice 5/24/2017 1 2 Types of Glaciers • Continental – Cover large areas, like continents – Due to cold global climates • Alpine – Cover mountain tops and sides – Due to Orographic effect 5/24/2017 2 GLACIERS - VALLEY AND CONTINENTAL 5/24/2017 3 Glaciers • Form when snow accumulation is greater than snow melting – Cause a build up of ice • Glacial movement is similar to streams (fastest in center) • Create "U" shaped valleys with nearly vertical walls and flat bottom 5/24/2017 4 5/24/2017 5 5/24/2017 6 Glaciers in North America over the past 2.0 x 106 years • Ice covered most of New York several times in the “recent” past • Most recently about 11,000 – 15,000 ybp. 5/24/2017 7 5/24/2017 8 The last major glacial period 5/24/2017 9 Erosion by Glaciers • Glaciers remove and carry sediments – Ice can be thousands of feet thick and thus very powerful. – Surface materials (like soil) are easily removed. – Sediments at the bottom of the ice act like sandpaper and scour the bedrock. • Continental and alpine glaciers have different erosional (and depositional) characteristics. 5/24/2017 10 5/24/2017 11 5/24/2017 12 5/24/2017 13 Glaciers • Create features like striations 5/24/2017 14 5/24/2017 15 Glaciers ….glacial polish –Where rocks within a glacier grind against bedrock 5/24/2017 16 Deposition by Glaciers • Mixed sized sediment drops vertically as glacier melts –Unsorted sedimentation –Sediments often scratched (striations) 5/24/2017 17 Glacial Deposition • This sediment is made of a variety of particle sizes 5/24/2017 18 Deposition by Glaciers • The large rocks left behind by glaciers are called glacial erratics – Large rocks not broken into small particles – Often different in composition than the bedrock upon which they sit 5/24/2017 19 NY Erratic 5/24/2017 20 Erratics in our area Based on this image, where did the erratics and other non -native rock in Harpursville come from? 5/24/2017 21 Deposition by Glaciers • Glacial till – Unsorted glacial sediment • Ranges from clay sized particles to boulders – stratified (sorted) sediment consists of glacial sediments carried by meltwater and deposited in an outwash plain 5/24/2017 22 Till- Sierra Nevadas 5/24/2017 23 • A wide variety of landscape features are created by glaciation 5/24/2017 24 These features are most often associated with alpine glaciations: 5/24/2017 25 5/24/2017 26 Drumlin-Cranes Beach MA • Drumlins- Oval shaped Moraine 5/24/2017 27 5/24/2017 28 Esker-MN • Esker- Rivers on ice bore a hole in the ice and flow under the sheet. Rocky material builds up and the stream bed is left behind as a ridge of rubble. Esker-WI—Note boulders carries by water 5/24/2017 29 Esker- NE WA 5/24/2017 30 Kettles- Large block of ice separates and becomes surrounded with debris 5/24/2017 31 How is a valley created by a glacier similar to and different from a valley created by a stream? 5/24/2017 32 U Shaped Valleys- Yosemite Valley- 5/24/2017 33 Hanging Valley- Yosemite Natl Park, CA 5/24/2017 34 Holgate Glacier 5/24/2017 35 Glaciers Fusing Yukon Canada Terminus 5/24/2017 36 Iceberg Calving Terminus 5/24/2017 37 Portimoreino 5/24/2017 38 Jones Beach NY is part of an outwash plain 5/24/2017 39 Glaciers Video Awsome! 5/24/2017 40 5/24/2017 41