Ground-Ice Mounds in Tundra
1942; Taylor & Francis; Volume: 32; Issue: 3 Linguagem: Inglês
10.2307/210383
ISSN1931-0846
Autores Tópico(s)Smart Materials for Construction
ResumoHE tundra in Arctic and sub-Arctic regions' is irregular and rough in detail but relatively featureless in broader aspect. Low, scattered mounds that interrupt the monotony attract immediate attention. Although the mounds differ in size and shape, most of them are a few feet high, many tens of feet in circumference, and gently rounded or slightly asymmetrical in cross section. The large and well-developed mound of Figure i is 6o feet long, 22 feet wide, and 6 feet high, with an egg-shaped ground plan and a slightly asymmetrical profile. This is one of the highest and largest mounds observed ifh the Wolf Creek area, and none appear to cover more than I500 square feet. Mounds a foot or two high and of large area are barely discernible, and small mounds are hard to distinguish from other minor irregularities of the tundra. Roughly circular or elliptical ground plans prevail, usually with an elongation in a downslope direction. Profiles parallel to the slope have a steeper downslope side (Fig. i), but profiles transverse to the slope and those of mounds in relatively flat areas are gently rounded. The ground over most mounds of fairly large size is broken by tension cracks (Figs. i and 3), the largest and deepest of which are near the crest of the upwarp and along its edges. In these places the mounds can be seen to consist of a core of clear ice mantled by a surficial hull, one to three feet thick, of gravel, sand, soil, and tundra vegetation. So far as could be determined, the lower surface of the ice core is essentially flat and the upper surface rounded in the shape of the mound. The ice is clean and fairly clear, containing a few bubbles without noticeable orientation. A crude vertical columnar structure is discernible as the ice melts or when it is broken by a pick. A cross section (Fig. 6) illustrates the structure of a mound. In the Wolf Creek area there are only four or five mounds of fairly large size in each square mile. They are located chiefly on gentle slopes in places where a greater than average supply of ground water circulates near
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