Lava cascade in Thunderbolt Distributary of Labyrinth Cave system

and a roof covered with lavacicles (fig.
25). The northwest end of The Bedroom
is a solid wall of dripstone-its appearance
seems to negate the idea that this
tube might once have extended farther in
that direction. Yet, 45 ft northeast of this
walled-in end of The Bedroom, a lava
tube with exactly the same trend is
present (map 3, pl. 1). Upstream, toward
The Bedroom, this tube is filled to its
roof with blocks of collapse breccia that
are almost completely penetrated and
sealed in by lava; downstream the tube is
open with a floor of frothy pahoehoe in
which are embedded many rafted blocks
of collapse material. A little farther
downstream this tube is again partly
blocked by a more recent roof collapse,
which occurred after volcanism had
ceased and the tube had drained.
Downstream through this network of
tubes is a point at the northeast end of
Applegate A venue where the three components
of the tube system merge into
one large tube 40ft wide. In another 50
ft, however, this large tube, The Lower
Chamber, turns sharply to the north and
Figure 25. Shark-tooth-shaped lavacicl
es on ceil ing of Catacombs Cave (see
fig. 14 and map 3, pl. 1). End offlashlight
at lower left for scale.
immediately spawns two branches from
its east side. The two branches unite
again downstream but continue to flow
along near-parallel courses with occasional
pillars such as the Wine Cask
between them. Additional subdivision is
present still farther downstream. By the
time one reaches The Bathtub, a northeast-southwest
section through The
Bathtub Drain intersects seven tubes
spread over an area 250 ft wide.
The branching tubes are typical of the
kind that can develop in either a large,
thick flow of basaltic lava or, more
likely, a thick succession of flow units
rapidly erupted over a sloping surface. A
major eruption will build a large lobate
ridge elongated downslope, which develops
a thick crust by congealing of the
lava on the top and sides of the flow. As
lava is fed into the still molten interior of
the flow, it begins to break out through
cracks in the front and sides of the partly
solidified flow , forming definite underground
tubes filled with traveling lava.
As lava continues to pour into and
through these developing tubes, complicated
anastomosing passages may result.
Further complexity also results from
distributary tubes that branch off from
the central tube plexus toward the margins;
these complications multiply if
rapidly fed lobes pile up on one another
and weld into flow units containing tubes
at different levels.
The Bathtub Area
The Bathtub lies at the center of an
area that is one of the most complicated
and therefore interesting parts of Catacombs
Cave (map 3, pl. 1). Within 80ft
of The Bathtub are five lava falls, three
lava cascades, one vertical shaft through
which lava tumbled, and over a dozen
lava tubes of various sizes, several of
which intertwine in a complex fashion.
To find The Bathtub, and The Bathtub
Drain within it, follow the trail 720
ft downstream from the Catacombs entrance
to the bottom of an 8-ft stairway.
Climb these stairs to reach the surface of
the lava that fills The Bathtub. It is a pool
of congealed lava 75 ft long and 25 ft
wide, evidently ponded after it had half-
filled a large lava tube. The source of the
lava, the cause of its ponding, and the
places where it spilled out after overfilling
The Bathtub are not immediately
apparent but can be worked out on
further examination. Walk northeast
along the Boxing Glove Chamber (away
from the stairs) and notice that the roof
of the lava tube gets progressively lower,
until, 120ft from the stairs and around a
gentle curve to the right, the ceiling of
the tube comes down to and passes
beneath the ponded lava. Note also that
over the last few feet, the ponded lava is
bowed up into pahoehoe ropes, showing
that in this part of The Bathtub lava was
creeping forward at a very slow rate
downstream toward the place where the
tube disappears beneath the lava fill. A
tube as large as this could easily carry
away the lava ponded in The Bathtub in
a matter of minutes. Evidently the tube
somewhere downstream was dammed,
perhaps by a roof collapse, until the
increasing hydraulic pressure and the
lava's rise in elevation caused it to spill
over into some nearby underground tube.
Return toward the stairs along the
southeast wall of the Boxing Glove
Chamber, and about halfway back notice
a small tube, partly filled with lava, that
exits The Bathtub eastward. Explore this
tube and in less than 10 ft you find lava
frozen as it spilled over a 9-ft fall into a
much larger tube below. At the base of
the fall the lava turned abruptly to the
right (south) and tumbled into yet another
tube 5-6ft lower. By using the map or,
by a tortuous crawl upstream, you will
find that this tube passes directly underneath
The Bathtub. Moreover, the tube
connects directly with the lava in The
Bathtub through a vertical hole that
forms the lower part of the feature named
The Bathtub Drain. This feature, however,
is more easily studied from The
Bathtub floor above than from its exit
into the lower tube. The Bathtub Drain
(fig. 26) is a funnel-like depression near
the southwest end of The Bathtub. The
upper part of the funnel walls reveals
how the lava of The Boxing Glove
Chamber floor cracked into crescentshaped
blocks and moved slowly down
the vertical shaft of the funnel. The more
liquid lava and loose blocks dropped
26 Selected Caves and lava-Tube Systems, lava Beds National Monument, California