Rock Glacier EarthCache
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The Denali Highway, one of America's remaining truly remote roads, connects the George Parks Highway and Richardson Highways allowing visitors to visit remote Alaska on a graded, summer accessible road while experiencing the beauty of the Last Frontier.
Rock glaciers are bodies of frozen debris with interstitial ice cement, ice lenses, or a core of massive ice. They belong to the most spectacular and most widespread periglacial phenomenon on earth. Their origin is still controversial with one group of scientists stating that they are strictly the result of periglacial processes, the other group argues that rock glaciers may also evolve from debris-covered glaciers.
Active rock glaciers move down slope mostly by internal deformation of ice, with speeds ranging from several centimeters/year to several meters/year. Inactive rock glaciers still contain some ice, but are not moving. Fossil rock glaciers do not contain ice, all the ice has melted, and the surface (particularly the front slope) is frequently covered by vegetation. The gradient of the front slope is less steep than that of active rock glaciers.
Rock glaciers may take one of three different shapes. Tongue-shaped glaciers are longer than they are wide while lobate glaciers are wider than they are long. There are also complex glaciers which are a mixture.
The surface is characterized by a coarse grained debris layer ("active layer"), which overlays frozen debris and/or ice. The surface of most active rock glaciers has well developed longitudinal and transversal ridges and furrows. The front slope of active rock glaciers usually has a steep gradient (40 - 45°), is bare of vegetation and composed of fresh, unweathered material. In the root zone of some rock glaciers a spoon-shaped depression is developed, which formed by the melting of massive ice under the debris layer.
Temperatures of the meltwater released from active rock glaciers are consistently very low during the whole melt season, being just a few degrees above freezing. This low water temperature indicates that the meltwater released at the rock glacier spring was in direct contact with ice when flowing through the rock glacier. Discharge of active rock glaciers is characterized by strong seasonal and diurnal variations. Water released from active rock glaciers comes from snowmelt, melting of permafrost and/or glacier ice, rainfall during summer thunderstorms and groundwater. Meltwater flows through the rock glaciers both on the surface of the permafrost ice (at the permafrost table) and deeper through channels in the ice and rock. The amount of discharge is controlled by the thickness of the winter snow cover, the size of rock glacier and drainage area, the presence of cirque glacier(s) in the drainage area, the thickness and grain size of the debris mantle/active layer, the groundwater supply and the weather conditions during the melt period, particularly summer thunderstorms, causing pronounced seasonal and diurnal variations.
To log this cache, e-mail the cache owner the answer for the following questions (you may need binoculars to see properly depending on weather conditions):
1) Based on what you read above, what shape of rock glacier is on the mountain to the north of the posted coordinates?
2) Observe the front slope of the glacier to the north. Does this appear to be an active or an inactive glacier?
Please post a picture of yourself with the rock glacier in the background.
Any log where I did not receive answers will also be deleted! To make sure I give you credit for your answers, please e-mail them to me at the same time that you log your find.
Any log with answers will be deleted.
Additional Hints
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