Lava cascade in Thunderbolt Distributary of Labyrinth Cave system

is reached in which the amount of ice
melted and vaporized in summer fluctuates
little from the amount of ice accumulated
during the winter months. It is a
sensitive equilibrium: the heat supplied
and the agitation of the air caused by a
large number of visitors passing through
a cave in summer increase melting;
visitors in winter add to the ice by
precipitation of moisture from their
breath. This is the reason that access to
Crystal Cave is restricted to small groups
of visitors on a limited schedule.
Ice in Crystal Cave occurs in four
main forms:
(1) Icicles and Ice Stalagmites.
Crystal-clear icicles form where water
drips from cracks in the roof or dribbles
over ledges, and ice stalagmites grow up
from the floor where falling water droplets
freeze on impact.
A spectacular drapery of coalesced
icicles festoons the southeast wall of the
lower level from 145 ft to 200 ft downstream
from the Blue Glacier Room near
the Dolphin, a 4-ft-high ice stalagmite
(see map 18, pl. 6). Individual icicles in
this drapery are up to 20ft long (fig. 61)
whereas others are coalescing and overlapping
shafts 3-15 ft long. All are so
transparent that details of the wall rock
behind them are clearly visible through
the 0.5- to 3-ft-thick covering. Ice stalagmites
have grown up from the floor to
meet the icicles in parts of this drapery
but are not conspicuous. On the other
hand, large stalagmites as much as 4 ft
high and several feet in diameter are
scattered along the floor of the cave in
front of the icicle drapery and for another
50 ft downstream. No correlation appears
to exist between the size of a
stalagmite on the floor and the size of an
icicle directly above it; some large icicles
have grown completely from roof to
floor without a companion stalagmite
rising to meet them (fig. 62). Variations
in the ratio of water supply to rate of
freezing appear to cause these differences
in size of icicles versus ice stalagmites.
A similar, smaller drapery of
icicles occurs at the upstream end of the
upper level and throughout Fantasy Passage.
One of the most beautiful displays of
icicles and other ice forms is found in the
Figure 61. Ice drapery on wall of Crystal Cave (see fig. 14 and map 18, pl. 6).
Figure 62. Ice stalactites from roof joined floor to form this ice fall in Crystal Cave
(see fig. 14 and map 18, pl. 6).
Crystal Cave 89