WORKING GROUP 6 
LANDEN 
369 
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 
travel. 
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