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Internal deformation occurs when the weight of the ice causes the deformation of ice crystals. This takes place most readily near the glacier bed, where pressures are highest. There are glaciers that primarily move via sliding, glacial quakes, and others that move almost entirely through deformation.
That is, locations farther north rise faster, an effect that becomes apparent in lakes. The bottoms of the lakes gradually tilt away from the direction of the former ice maximum, such that lake shores on the side of the maximum (typically north) recede and the opposite (southern) shores sink. [17] This causes the formation of new rapids and rivers.
Ice dam forming on slate roof. An ice dam is an ice build-up on the eaves of sloped roofs of heated buildings that results from melting snow under a snow pack reaching the eave and freezing there. Freezing at the eave impedes the drainage of meltwater, which adds to the ice dam and causes backup of the meltwater, which may cause water leakage ...
Sediment clasts suspended in the ice at the bottom of the glacier have greater friction with the ground than the ice does. This causes the sediment to be slowed down disproportionately to the ice and eventually fall out or get stuck in the ground beneath the ice. [25] The till may also be deposited as the glacier melts and retreats.
[15] [16] [17] Speeds can be faster for small-scale convection occurring in low viscosity regions beneath the lithosphere, and slower in the lowermost mantle where viscosities are larger. A single shallow convection cycle takes on the order of 50 million years, though deeper convection can be closer to 200 million years. [18]
In the summer, glacial streams experience high stream flow because of ice melt. [8] The high flow is characterized by high turbidity and sediment transport, which reduces the biomass of the resident periphyton. [8] At the end of summer, ice melt is reduced and stream flow decreases, causing an increase in the periphyton population. [8]
For this edition of the Scrub Hub, we are looking at ice dams: What are they, what causes them, and what problems are they making worse?
δ 18 O, a proxy for temperature, for the last 600,000 years (an average from several deep sea sediment carbonate samples) [a]. The 100,000-year problem (also 100 ky problem or 100 ka problem) of the Milankovitch theory of orbital forcing refers to a discrepancy between the reconstructed geologic temperature record and the reconstructed amount of incoming solar radiation, or insolation over ...