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the effect of glaciers
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How Glaciers Flow
- Glaciers flow under the force of gravity as snow accumulates on the upper parts of the glacier and wants moves down slope.
- The snow compresses to become ice and flows through the glacier into the ablation zone where it is lost.
- If the accumulation equals the ablation than the glacier is said to be in equilibrium and its position will not change. This does not mean that the ice will not flow!
Accumulation Zone
The area where inputs occur into a glacier system. This usually occurs near the top of the glacier or ice sheet and such inputs to the system include snowfall, wind blown snow, rain and avalanches.
Ablation Zone
The region in which more mass is lost than gained in a glacier system. This usually occurs at the end and sides of the glacier. Forms of losses include wind ablation, avalanching, iceberg calving and melting.
Glaciers flow through three different mechanisms: (1) by internal deformation; (2) by basal sliding; and (3) by subglacial deformation.
Glacier Flow Mechanisms
Internal Deformation
Ice deforms under its own weight due to gravity and the movements of tiny ice crystals. Thicker and warmer ice deforms more rapidly although the overall movement is very slow, only around tens of meters a year. There are two main processes of internal deformation; creep, which forms fold structures, and faulting, which occurs when ice cannot creep fast enough and forms superficial tensional fractures.
Basal Sliding
Enhanced Basal Creep - Stress concentrations around the upstream side of an obstacle result in locally high strain rates which causes ice to accelerate around the obstacle. The basal ice continually modifies its shape to allow a continued sliding. This process works best when the obstacle is over 1m in size.
Regelation - The process allows glacier ice to slide over rough beds by melting and refreezing on the downglacier side. It occurs as the most resistance to glacier movement is provided by the upstream side of obstacles. This results in locally high pressures and the consequent encouragement of ice melting immediately upglacier of the obstacle. The resulting meltwater migrates to the lower pressure area downstream where it refreezes. This process is most effective when objects are less than 1m in size.
Subglacial deformation
Sediment has a lower yield strength than rock and ice and so it is deformable. As the sediment deforms, it moves the ice sheet with it.
Ice Velocites
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The surface velocities of a glacier can be measured quite easily using GPS.
A good description of a glacier is given by Jim Wickwire in his book “Addicted to Danger.” In it he says, “A glacier is not a fixed, solid thing. It flows like a river, with currents, some parts smooth, others rough” (Wickwire, 1998, p. 1). This happens to go along with Webster’s definition, in that a glacier must be moving, either because of gravity or because it’s spreading out underneath itself due to additional accumulations. (Meeriam-Webster, 2000, p. 493).
Firstly, the landscape around would be dramatically eroded. Whereas a glacier pushes out of the way objects in its path, and erodes the surrounding area through a combination of ablation, plucking and freeze-thaw, the glacier itself commonly hides the features it creates, but when the glacier melts, features such as cirques, horns, arêtes, hanging valleys and waterfalls can be seen. Also, the melt water would itself cut a small v-shape in the base of the U-shaped valley created by the glacier. The stones in the river, and deposition would cause this. Lateral and terminal moraines would also be created after the glacier deposits some of the rocks and dirt that it will have picked up as it moves.
... Kristovich. "Observations of the Cross-Lake Cloud and Snow Evolution in a Lake-Effect Snow Event." Monthly Weather Review 139.8 (2011): 2386-398. Print.
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Polar ice is sea ice created from the freezing of sea water, ice sheets and glaciers. These in turn are formed from the build up and compaction of fallen snow. Both the ice sheets and glaciers cover vast areas of the Polar Regions. This polar ice is hugely important to our globe and takes up a large part of it. Global sea-ice coverage averages about 25 million kilometers square; this is the area of the entire North America continent. The ice sheets, which cover the land, with the glaciers cover about 15 million kilometers square; this is almost 10% of the Earth’s land area, with the majority on Antarctica (Earthobservatory.nasa.gov, 2013).
Introduction: A phase change is a result from the kinetic energy (heat) either decreasing or increasing to change the state of matter (i.e. water, liquid, or gas.) Thus saying, freezing is the phase change from a liquid to a solid which results from less kinetic energy/heat. Also, melting is the phase change from a solid to a liquid which results from adding kinetic energy/heat. So, the freezing and melting point of something is the temperature at which these phase changes occur. Therefore, a phase change will occur when a vial of 10 mL of water is placed into a cup of crushed ice mixed with four spoonfuls with 5 mL of sodium chloride for 30 minutes. If 10 mL of water is placed in an ice bath, it will then freeze at 5 degrees Celsius because the kinetic energy will leave quicker with the ice involved. The purpose of this lab is to observe what temperature the water must be to undergo a phase change.
To begin with, the landing of the snow on the road caused many damages to them. This was because the levels on which the roads were raised were in different proportions. This, therefore, prevented lack of flow to be experienced on the roads. Moreover, the cracks that were observed on the roads came about because of the difference in the temperatures of the country.
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