Lava cascade in Thunderbolt Distributary of Labyrinth Cave system

es of plaster clog its continuation completely.
Near-Surface Nature of the
Headquarters and Labyrinth Area Tubes
From our investigations of these
Headquarters area lava tubes, one conclusion
needs to be emphasized: all of
them described so far, with the possible
exception of the eastern distributary of
Mushpot Cave, are small near-surface
tubes. If you compare map 1 and map 2
(pl. 1), it appears at first glance that all
of the lava active in making the remarkably
extensive bifurcating caves of the
Labyrinth area was finally funneled
downstream into the tiny single tube
containing the Thunderbolt entrance.
This interpretation is, of course, nonsense.
What is missing in such an analysis
is the fact that nearly all the tubes in
both Labyrinth and Headquarters areas
disappear downstream because lava
filled to their roofs; thus, further tracing
of them is impossible. Only the parts that
have drained out after cessation of volcanism
can be entered, mapped, and
studied.
Unquestionably, deep beneath the
Headquarters area are scores of tubes
filled to their roofs with lava. One
example we studied is the eastern distributary
of Mushpot Cave, where 70ft
of the roof of a deeper, now-filled tube
is visible. We also traced Mushpot, parts
of Lava Brook, and Arch Caves downstream
to where they are filled with
congealed lava.
Well over 85 percent of the deep
underground lava "plumbing" system in
Lava Beds National Monument was
filled with congealed lava and is therefore
inaccessible. But accidents of various
kinds have, in places, preserved
short sections of intact lava tubes. Examples
of large remnants in the monument
are Crystal, Craig, and Post Office
Caves. Indian Well (map 1, pl. 1) and
Sentinel Caves (map 7, pl. 2) are easily
accessible small remnants on a line upstream
with Ovis Cave, Crystal Cave,
and the deep tubes underlying Natural
Bridge. Downstream their extension can
be traced by breakdowns at the entrances
into Post Office and Silver Caves and
eastward to a possible junction with
Craig Cave.
Figure 19. Interior of Arch Cave (see fig. 14 and map 1, pi 1) showing jagged
benches and heaved and broken floor.
We now tum to a description of a
much collapsed and battered small remnant
of two large tubes within this long
chain of breakdowns-Indian Well
Cave.
Indian Well, Doc Yock, and
Stinking Caves
Eastward approximately 450 ft from
the Visitor Center, and across the main
road at the head of a deep breakdown, is
Indian Well Cave (see map 1, pl. 1). This
cave is very different from the nearsurface
small-diameter caves described
previously. J.D. Howard named the cave
Indian Well because of the pool of water
that develops in the deep central part of
the cave after the spring runoff. The pool
is not permanent; in many years the water
is lost by evaporation or downward
percolation within a few weeks to a
month. Nevertheless, in this dry area of
no surface streams, it has furnished a
welcome supply of water to both animals
and humans.
The entrance to Indian Well Cave is
spectacular. At the south end of the
breakdown a sliced-off section of the
upper half of the lava tube rises over the
pile of collapse rubble on the tube's floor
in an impressive arch, 60 ft wide and 20
ft high. Continuing southward into the
cave, the walls narrow until, 55 ft from
the entrance, the cave is only 30ft wide.
It widens again where the west wall and
part of the roof have slumped inward and
dumped so much rubble into the cave that
the trail must tum and hug the east wall
to avoid it. Throughout the first 120ft of
the cave no original features (such as
lavacicle roof, dripstone walls or pahoehoe
floor) are preserved, except as broken
fragments on the ends of fallen
blocks. The floor is a hummocky blanket
of collapse rubble, and both roof and
walls show places where large blocks
have tumbled to the floor. However, 125
ft from the entrance, an alcove extends
into the east wall of the cave 10 ft above
the rubble-covered floor. This remnant
of lava bench is the only primary feature
found in this part of the cave (fig. 20).
At the south edge of the alcove the
rubble on the floor of the cave drops off
abruptly to the south in a low scarp,
18 Selected Caves and Lava-Tube Systems, Lava Beds National Monument, California