Later it advances again and reshapes the moraine into

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Unformatted text preview: ngell-St. Elias NP, SE AK Lateral and Medial Moraines – Kennicott Glacier Kennicott The Origin of Drumlins The Glacier retreats, leaving behind a terminal moraine. Later it advances again, and reshapes the moraine into a drumlin. Drumlins Rochester,NY Rochester,NY Glacial Deposits - Drift Glacial • TYPE 2: SORTED • Outwash: sorted stratified sediments deposited by meltwater streams • Loess: wind erosion of drying outwash silt. • Eskers: sinuous meltwater deposits of sand and gravel underneath ice Origin of Eskers Origin Eskers in Coteau des Prairies, South Dakota Eskers Effects of Glaciation Effects • Change Climate – increase precipitation locally - pluvial lakes • Depress continents & lateral rebound • Drop sea-level: alter coastlines • Form continent-wide Dams – Divert streams – Ohio and Missouri rivers Formation of Terraces due to Crustal Rebound Formation Lowered Sea-level - Landbridge Lowered Glacier Distribution 20,000 ya Glacier Approximate Maximum Lowered Sea-level exposed continental shelf Lowered The Creation of Glacial Lake Missoula The Purcell Lobe blocks Clark Fork River The Draining of Glacial Lake Missoula Repeated many times, last time 13000 kya Giant Ripples of the Missoula Flooding Giant Causes of Ice Ages Causes • Plate Tectonics Moves Continents to Poles Raises mountains above snowline • Orbit distance, Axis Tilt and Wobble – Moderates solar radiation north of 65 N – Milankovitch Cycles ~ 100,000 years – Low summertime radiation 65 N, glaciers expand Milankovitch Cycles Discussion: cool summers and wet winters Moisture content of air masses 100,000 years Warm Wet Winter Cool Summer Cold Dry Winter Hot Summer 41,00...
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This document was uploaded on 01/26/2014.

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