34 
Fig. 15. Photo of hoarfrost crystals on snow 
from dirt patch. 
Fig. 16. Snow with sastrugi 
vegetation. 
and blades of 
in this area was shallower than the average 
thickness in 1973, just as it was in 1972 (see 
traverse 1 data in Tables 6 and 7). It was also 
wind sculptured and had bits of vegetation 
protruding through it (Figs. 15 and 16). When 
melting begins it spreads outward from the bits 
of protruding vegetation, which act as centers 
for ablation, as do the bare soil patches. 
The progress of snowmelt can be seen by 
looking at sequential aerial photographs that 
were taken between 24 May and 30 June 1972. 
No melt had occurred by 24 May except along 
heavily traveled roads. There are five sequences 
of photographs, and their locations are indicated 
by the rectangular areas blocked out in Fig. 1. 
The sequences are as follows: 
Sequential Photographs: Set Number 1. 
BP pad ‘‘N” area during breakup 1972 
24 May 
5 June 
9 June Arrow located on west side 
12 June of Pad N and pointing east. 
15 June 
30 June 
>p aoe 
Sequential Photographs: Set No. 2, 
BP Gathering Center No. 1 during breakup 1972 
a. 24 May 
b. 5 June Arrow located on east side of 
( 11 June G.C. No. 1 and pointing west. 
d. 13June 
Sequential Photographs: Set No. 3. 
BP Gathering Center No. 3 during breakup 1972 
a. 24 May 
b. 5 June Arrow located on east side of 
o 9 June GC No.3 and pointing west. 
d. 15 June 
Sequential Photographs: Set No. 4. 
IBP Tundra Biome intensive study site 
during breakup 1972 
a. 24 May 
b. 5 June 
c. 11 June Arrow located at intersection 
d. 13 June of BP Spine Road and Put 
e. 15 June River No. 1 Road and pointing 
f. 30 June south. 
