Lava cascade in Thunderbolt Distributary of Labyrinth Cave system

For a short distance below the collapse
amphitheater, passage is blocked
by the fill for Tickner Road and by
collapse breccia. Access to the surface is
provided by a crawlhole that emerges on
the south edge of the road (South Road
entrance) and reentry to the cave by both
a small crawlhole (North Road entrance)
and a large oval roof collapse 250 ft
north. There are also three holes through
the roof of the tube between Tickner
Road and this large oval collapse (see
map 9, pl. 3).
The most striking features in Tickner
Cave between the road and the oval
collapse are large remnants of the Balcony
flow, which hang as true balconies
above the present floor of the cave.
These balconies have turned-down edges
and curl back into an overhang in places.
Of particular interest are remnants of the
flow (one oval, the other pear-shaped),
which are not attached to the cave walls,
standing isolated within the drained area
(map 9, pl. 3). The oval remnant has a
top that is tilted up on its edges like a
saucer; the pear-shaped one is tilted
downstream, but the direction and
amount of tilt are not the same as that of
the nearby wall-attached balconies. The
most logical explanation is that these two
remnants broke loose from the east wall,
as the lava flood withdrew from beneath
them, and then slid toward the central
part of the cave. The surface of these
isolated remnants is lower than that of
adjacent wall-clinging balconies, a fact
which supports the inference that they
slid downhill from their former positions.
The floor of the cave in this area
is a jumble of slabs of collapsed balcony
(map 9, pl. 3).
One of the most instructive areas of
balcony collapse is a 100-ft stretch of
Tickner Cave between the northeast edge
of a large oval roof collapse and the point
downstream where it narrows abruptly
near the north side of a pillar in its west
wall. In the wide cavern upstream from
this narrow spot a remnant of the Balcony
flow 80 ft long and 5 ft wide hangs
from the east wall 8-12 ft above the floor
of the cave. On the opposite (west) wall
of the tube the remnant counterpart is
only 1-2 ft wide and is missing from the
southern part of the cave wall. On the
floor of the cave, however, rests a huge
block from this balcony. It is 45 ft long
and tapers in width from 14 ft at its south
end to 2 ft at its north end. This balcony
remnant toppled out from the west wall
and now lies on its side, with its pooled
Figure 41. Buckled floor plates of Tickner Cave (see fig. 4 and map 9, pl. 3) formed
when interior of lava flow drained away, and chilled pahoehoe surface lost support.
pahoehoe surface vertical and facing
east. Molten lava was evidently flowing
through the tube when the block broke
away from the west wall and toppled
eastward, because the upturned face of
the block shows spatters of lava and
pieces of fallen lavacicles upon it. The
relatively smooth broken-off wall of the
cave west of this block contains small
ridges and troughs running horizontally
that can be matched exactly with corresponding
features on the upward-facing
surface on the fallen block.
The broken-off west wall contrasts
noticeably with the east wall-the east
wall is embellished by one of the most
spectacular and photogenic displays of
dripstone in any cave described herein.
The last thin coating of brown dripstone
that ran down this wall probably came
from the liquid lava splashed against it
when the block from the west balcony
toppled.
The pillar at the downstream end of
this room has a small tube routed through
its west side. The floor of this small tube
hangs a few feet above the surface of the
balcony. Downstream 50 ft farther, the
intact balcony becomes the actual floor
of the cave and forms a wide natural
bridge within the cave. Beneath this
bridge, molten lava was conveyed downstream
through a tube-in-tube. This culvert-like
drain is now only 2-5 ft in
diameter because successive linings of
lava plaster almost closed off the space
between its walls, roof, and floor. Only
the downstream one-fourth of this tubein-tube
is large enough to crawl into. The
broken-off upper end of the tube reveals
the linings that successively diminished
the size of the tube-in-tube. The thin
edge of the large toppled block of balcony
described previously is jammed
against the east wall, alongside the upstream
end of this culvert.
At its downstream end the tubein-tube
emerges onto a lava floor at the
west edge of another amphitheater-like
lava cascade, similar to but not as high as
the one above Tickner Road. This new
floor, 4-7 ft lower than the balcony
level, disappears another 40 ft downstream
beneath the rubble of a 200-
ft-long roof collapse. Apparently, the
lava in equilibrium with this lower-floor
50 Selected Caves and Lava-Tube Systems, Lava Beds National Monument, California