Transcript Soils
Erosion & Deposition by Ice 7/18/2015 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 7/18/2015 2 GLACIERS - VALLEY AND CONTINENTAL 7/18/2015 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 7/18/2015 4 7/18/2015 5 7/18/2015 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. 7/18/2015 7 7/18/2015 8 The last major glacial period 7/18/2015 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. 7/18/2015 10 7/18/2015 11 7/18/2015 12 7/18/2015 13 Glaciers • Create features like striations 7/18/2015 14 7/18/2015 15 Glaciers ….glacial polish –Where rocks within a glacier grind against bedrock 7/18/2015 16 Deposition by Glaciers • Mixed sized sediment drops vertically as glacier melts –Unsorted sedimentation –Sediments often scratched (striations) 7/18/2015 17 Glacial Deposition • This sediment is made of a variety of particle sizes 7/18/2015 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 7/18/2015 19 NY Erratic 7/18/2015 20 Erratics in our area Based on this image, where did the erratics and other non -native rock in Harpursville come from? 7/18/2015 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 7/18/2015 22 Till- Sierra Nevadas 7/18/2015 23 • A wide variety of landscape features are created by glaciation 7/18/2015 24 These features are most often associated with alpine glaciations: 7/18/2015 25 7/18/2015 26 Drumlin-Cranes Beach MA • Drumlins- Oval shaped Moraine 7/18/2015 27 7/18/2015 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 7/18/2015 29 Esker- NE WA 7/18/2015 30 Kettles- Large block of ice separates and becomes surrounded with debris 7/18/2015 31 How is a valley created by a glacier similar to and different from a valley created by a stream? 7/18/2015 32 U Shaped Valleys- Yosemite Valley- 7/18/2015 33 Hanging Valley- Yosemite Natl Park, CA 7/18/2015 34 Holgate Glacier 7/18/2015 35 Glaciers Fusing Yukon Canada Terminus 7/18/2015 36 Iceberg Calving Terminus 7/18/2015 37 Portimoreino 7/18/2015 38 Jones Beach NY is part of an outwash plain 7/18/2015 39 Glaciers Video Awsome! 7/18/2015 40 7/18/2015 41