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Published byΚλειώ Ασπάσιος Modified over 5 years ago
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Glacial Deposition Glacial Drift – general term for glacial deposits
Till – direct ice deposits left as sorted or unstratified debris Stratified drift – sediments deposited by glacial meltwater sorted by size Glacial erratics – large rocks (boulders) left behind by ice movement
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Moraines Created by the deposition of glacial sediment Several types:
Lateral moraine – forms along the side of a glacier Medial moraine – forms where two lateral moraines join together Terminal moraine – eroded debris dropped at a glacier's farthest extent End moraine – formed where a glacier paused after reaching a point of equilibrium
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Continental Glacier Deposition
Lacks the intricate features of alpine glaciers Lateral and medial moraines are not found in continental glaciers Till plains form behind end moraines Low & rolling relief Coarse sediment that is unstratified Outwash plains are found beyond morainal deposits Kettle lakes can form as a result of sediment accumulating around a large ice block Steep sided hole Walden Pond in Mass. Streamlined hills can form Roche moutonnee – erosional hill formations Drumlins – depositional hill formations
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Roche Moutonnee
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Periglacial Landscapes
Periglacial refers to weathering from freeze-thaw seasonality Near-permanent ice cover or at high altitudes with little to no snowfall Permafrost Frost action Ground ice Commonly found in high latitude (tundra) climates or in high elevation (alpine) climates
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Permafrost Develops when soil or rock temperatures remain below 0*C for at least 2 years Based solely on temperature, not water content Continuous permafrost – perennial in nature Discontinuous permafrost – unconnected patches of permafrost Permafrost is absent on southward (sun) facing slopes, areas of warm soil, or areas insulated by snow
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Permafrost Features Active layer Talik
Seasonally frozen/thawed ground between subsurface permafrost layer & ground surface Subjected to daily freeze-thaw cycles Higher temperature results in thicker active layer Lower temperature thins active layer & increase permafrost thickness Talik unfrozen ground that may occur above, below, or within a body of discontinuous permafrost
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Ground-Ice Frozen subsurface water found in regions of permafrost
Freezing front Boundary between frozen and unfrozen soil Associated with frost action occurs when sufficient water freezes and expands saturated soils and rocks Frost heaving (vertical movement) Frost thrusting (horizontal movement) Ice wedges develop when water enters a crack in the ground and freezes Range in size, but can become significant over long periods of time
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Gelifluction Similar process to solifluction
Flow of soil due to saturation Occurs as a result of poor soil drainage in areas of permafrost or ground ice Can result in flattening a landscape Identifiable sagging surface patterns Easily identifiable among human constructions
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Paleoclimatology & Ice Ages
Ice Age – a time of generally cold climate that includes one or more glacials, interrupted by brief warm spells known as interglacials Ice cores provide evidence for past climate fluctuations Obtained through oxygen isotope analysis Analysis of past climate events helps us understand present conditions on the planet
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Medieval Warm Period & Little Ice Age
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Glacial Advance & Retreat in the Great Lakes
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Paleolakes
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