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Transactions of the Symposium on Photo Interpretation

Fig. 3. Parallel ridges or waves in the “featureless” surface of the Polar Plateau near
86°10' S., 34°00' E.
formations due to thermal changes in the ice or to motion of the ice over sub
merged obstacles. Crevasses are the most dangerous surface features in the
Antarctic. They are also the most significant ice features because of the infor
mation they reveal about glacier structure, glacier movement, and subglacial
topography [Roscoe 1953]. Undisturbed crevasses may close and drift over
without leaving a trace; as such they present considerable danger to surface
Oblique and vertical photographs are considered to be the best sensors for
recording crevasses but there is no positive method of detecting them. Open
crevasses show up as black slashes in the white surface. Snow-covered individual
are crevasses more difficult to detect but the overall crevasse system or pattern
can often be recognized. Bridged crevasses, difficult to see from the surface,
sometimes are easily identified on photographs by the lighter tone of the drift
snow in the depressed bridges, by holes and exposed linear portions of the
crevasse system, and by the formation of right-angle snow drifts (fig. 4).
General-purpose mapping
Most of the photography of the Antarctic is trimetrogon photography taken
with a three-camera arrangement giving horizon-to-horizon coverage. Fig. 5