Valleys u shaped valley in tracy wilderness

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Unformatted text preview: ite Valley Glaciers Valley • Erode a large quantity of bedrock and sediment • Convert V-shaped stream valleys into Ushaped glacial valleys. U-Shaped Valley in Tracy Wilderness, Southeastern Alaska U-Shaped Valley Seawater Flooded U-Shaped Valleys: Fjords Seawater Valleys: Bela Bela Fjord, BC When glaciers melt, sea-level rises Erosion by Continental Glaciation Erosion • Erosional Landforms much larger in scale than alpine glaciers – Whalebacks – huge Roche Moutonée – Huge U-shaped troughs – Finger Lakes, Great Lakes, Puget Sound, Loch Ness were all once stream valleys excavated by Ice Sheets Erosion of Preglacial Lowlands (Finger Lakes) Erosion Erosion of Lowlands (Great Lakes, Finger Lakes) Erosion Superior M i c h i g a n Huron Ontario Erie Source: U.S. Dept. of Interior, USGS Eros Date Center Glacial Deposits - Drift Glacial • Collectively called Glacial Drift • TYPE 1: UNSORTED • Glacial Till: unsorted, unstratified sediments deposited by melting ice. – May contain glacial erratics – Often accumulates in glacier’s channel and at its terminus as a Moraine: – Terminal Moraine: hills of sediment left by a glacier’s retreat. – Terminal Moraines may be reshaped by a later glacial advance into Drumlins: rounded elongated hills perpendicular to their original orientation Advance & Retreat: Moraines Advance Note moraine, retreat or stationary Stationary Analogy: Escalator Stationary & Retreat: Moraine at Terminus Stationary Large Granite Erratics Lateral and Medial Moraines Lateral Wra...
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