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Unformatted text preview: Lab 6: Lab: Water, Wind and Ice Ice Eolian (aeolian) Eolian Prevailing wind direction (dominant) controls primary shape of feature controls Dunes Yardangs Dust devils Water - Fluvial Processes Water Unchannelled water-flow (runoff, or sheet flow) channeled water-flow (rivers and streams - fluvial fluvial environments), lakes (lacustrine environments), and environments), seas and oceans (marine environments). seas Dendritic- cut Dendritic cut V-shaped channels or valleys from flowing water (rainfall) water Viking Orbiter image 606A56, centered at 42.5°S 92.6°W. Credit: NASA/JPL/Viking Imaging Team. Ice - Glacial Processes Ice Glaciers: Glaciers: Large, slowly moving masses of ice, and are formed from compacted snow. snow. U-shaped valleys. Credits: ESA/DLR/FU Berlin (G. Neukum). Martian north polar ice cap shows layers of water ice and dust in perspective view. The cliffs are almost 2 kilometres high and the dark material in the caldera-like structures and dune fields could be volcanic ash. Layers averaging 50 meters in thickness are seen in the cliff face and surrounding areas, which are highlighted by occasional white patches of frost. The regularity of the layering suggests that it comes from periodic changes in the orbit of Mars - a relationship that, on Earth, may be at least partially responsible for ice ages. These orbit changes may affect the frequency and intensity of global dust storms, in turn varying the amount of material available to form layered terrain.
The cliff is apparently an erosional feature; the variety of scarps shows the complexity of erosion in the polar regions. Credits: ESA/DLR/FU Berlin (G. Neukum). •Mosaic of images showing outflow channel emerging from chaotic terrain. Oblique view, looking south, of the source region of an apparent flood. The channel starts full scale in a region of chaos enclosed by cliffs. Possible mechanisms for producing such a relation are rapid release of water from buried aquifers or the melting of ground ice by volcanism. Viking image P-16983; 1°S, 43°W. Image artifacts: changes in grey-scale on image in approximately north-south lines across image are joins between images. Oblique view of image shortens features in direction of view (to the south - slightly right of up). view Questions to Consider What evidence is there that the source for the surface water cut the source main channel shown in the image was ground water, not surface water? main What is the age of the channel with respect to the majority of the impact craters? impact Mars Example Answers Answers
Collapse Collapse features and other tectonic activity at the right end of the channel suggest that groundwater withdrawal caused these features (This complex terrain to the right of the head of the channel is known as Chaotic Terrain). Terrain No fresh impact craters visible in the channel. •No dendritic drainage pattern characteristic of surface rainfall A few features that look as if they could have been impact craters are visible in the few •Braided drainage pattern becomesflowed around them. The main channel very high channel, but they look as if water evident, characteristic of rivers with a narrows sediment load (sediment crater to the north of the channel (below the channel in the close to a large impact is deposited in the river channel and the river makes new channels around its own sediment. Theejecta may have hadof the channel without a image), possibly indicating the crater abrupt appearance some influence on the dendritic drainage pattern and subsequent characteristics of a braided stream direction of the channel. demonstrate that the channel was probably cut by running water, but there is no Channel is younger than the impact craters. Channel younger evidence origination of the flow from surface water.
•Subsurface, or groundwater. ...
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- Spring '09