Lava cascade in Thunderbolt Distributary of Labyrinth Cave system

Deep collapse trenches terminate
Ovis Cave at either end. They mark
positions along a system of large lava
tubes at least 6 mi long, which extends
from Mammoth Crater (fig. 4) to beyond
Post Office Cave. This system of tubes
may extend to Craig Cave and beyond.
Paradise Alleys
The intertwining tubes of the Paradise
Alleys can, for convenience, be
divided into three levels (map 4, pl. 2),
although most of the upper level is only
a partially developed drained balcony
within the middle level.
Lower Level
High on the east wall of Ovis Cave,
just below the roof and near the collapse
that terminates the cave's extension to
the south, a small lava tube branches off.
This small eastern distributary hangs 25
ft above the rubble-covered floor of Ovis
Cave and is the head of the lowest and
probably oldest level in the Paradise
Alleys distributary system. Within 20 ft
of its beginning, however, the floor of
this tube is left hanging as a balcony on
the walls of a second and slightly larger
tube. This tube trends northeast from its
head on the north wall of an east-trending
shallow basin, which branches from the
main collapse trench to a point 40 ft east
of the head of Ovis Cave (map 4, pl. 2).
After they join, both the balcony and the
floor of the tube below it tum to the
northeast in a series of lava cascades.
They pass completely beneath the much
wider middle level of Paradise Alleys.
The middle level originated and flowed
north from the east end of the shallow
collapse basin.
Most of the accessible length of the
lower-level tube shows lavacicles and
dripstone walls whereas its original pahoehoe
floor is littered with collapse
blocks. Downstream 70 ft below this
passage's entrance, a 6-ft-diameter rafted
block half-closes the tube. The upper
surface of this rafted block is decorated
by many broken and distorted lavacicles
and by lava, which coated it during its
transit along the tube. Downstream 180
ft farther from the entrance is a hole in the
left (west) wall of the lower level tube,
10 ft above its floor, which provides
ladder access to the middle level of
Paradise Alleys. From here visitors can
leave via the Paradise Alleys entrance,
another 80 ft downstream. Downstream
45 ft from the foot of the ladder, the
lower-level tube is blocked to further
entry by a roof collapse.
Middle Level
Of these three tubes, the 40-ft-wide
middle-level passage is the largest and
transmitted the most lava. Only 240ft of
its length is accessible because its continuation
downstream below the Paradise
Alleys entrance is completely buried by
collapse debris. Unquestionably it extended
beneath the partly collapsed skylight
just to the east, and from there it
extended beneath the upper level to a
subterranean junction with the lava lake
that once filled the Catacombs Basin.
Upper Level
The upper level of the Paradise Alleys
tubes begins as a balcony hanging on
the east wall of the middle level tube 80
ft upstream from the Paradise Alleys
entrance. Here, its rounded upstream end
can be entered by climbing a 5-ft ladder.
Whereas the middle-level tube bends
almost 90° at the entrance to Paradise
Alleys, this adjacent upper-level tube
continues straight as a smaller tube.
From the entrance alcove one can walk
downstream for 75 ft to where the tube
emerges into a former skylight whose
walls have been greatly enlarged by
late-stage collapse. As the upper level
leaves this skylight downstream, however,
the tube changes drastically in
character. It becomes larger, 25-40 ft
wide, and much of it-especially to the
northeast-appears to be filled almost to
the roof with lava. Moreover, much of its
pooled lava floor has collapsed (fig. 29)
into a lower tube. This is best shown by
a traverse upstream beginning from its
northeast end, where lava fill reaches the
roof and blocks access to the northeast;
here a jumbled mass of floor blocks lies
just below small balcony remnants still
attached to the walls. On the left (northwest)
wall a huge 30-ft slab of the
balcony is detached from the wall and
now lies on its side atop fractured blocks
of the subsided floor. Another 80 ft
upstream where the ceiling is lower, a
remnant of balcony crosses the tube and
Figure 29. Original pahoehoe floor of upper level Paradise Alleys tube (see fig. 14
and map 4, pl. 2) collapsed when molten lava withdrew underneath chilled surface.
Ovis Cave and Paradise Alleys 31