Lava cascade in Thunderbolt Distributary of Labyrinth Cave system

low depths along fissures. Many small
spillover lobes of lava were formed
during the final stages of eruptive activity.
The material that built this lava field
was transported almost entirely through
lava tubes; the main tubes preserved are
Tickner and Berthas Cupboard Caves.
J.D. Howard explored these features in
the 1920's (his notes are on file at the
Visitor Center). He named Tickner Cave
and the Tickner Chimneys after H.C.
Tickner, an early freighter who lived in
Yreka and pioneered the Tickner Road
(map 9, pl. 3), an important wagon route
in the late 1800's.
Howard also found a cave at a lower
level, which extends the cave system to
the northeast, and named this deeper
level Berthas Cupboard Cave in honor of
Bertha Heppe, the wife of an early
homesteader in the area. The word "cupboard"
refers to the shelf-like openings
and irregular small grottos that lie between
flow units of lava in the southeast
comer of the well-like breakdown forming
the main entrance. They are shown in
a schematic cross section on map 9, plate
3 and also in figure 37.
Tickner Road, a little-traveled dirt
road through the logged-over forest just
south of the monument boundary, is the
only access road to this area. Tickner
Road crosses a collapsed and filled part
of Tickner Cave (map 9, pl. 3) at a point
about 1 mi (by road) east of the junction
of Tickner Road with the Medicine Lake­
Lava Beds Road. The caves are unmarked;
the land survey location of this
crossing is in the NE 1 /4 sec. 5, T. 44 N.,
R. 4 E. An abandoned logging road joins
Tickner Road 200 ft west of the Tickner
Cave crossing and provides access to the
Tickner Chimneys farther upstream to
the south.
The position of Tickner and Berthas
Cupboard Caves is easily located because
of the line of collapse pits and
trenches formed along roof cave-ins (fig.
38). This line is at the center of the lava
flow, which trends north and then northeast.
The surface of the ground slopes
away on either side. Near the downstream
end of the lava field, Berthas
Cupboard Cave is so filled with ponded
lava and collapse debris that it can no
longer be traversed. The underground
tube, however, must have continued
northeast because small patches of aa
broke through and welled out of cave
roofs at points along the eastern continuation
of this line.
Farther upstream, during early and
late stages of volcanism, lobes of pahoehoe
flowed from skylights and fissures in
the roofs of the Tickner and Berthas
Cupboard tubes. These spillover lobes
were important components in building
the apical ridge along the sloping surface
of the lava flow.
Tickner Cave
The upper entrance to Tickner Cave
is at the northeast end of a lava chute 10
ft wide that increases from 2 to 10 ft in
depth downstream. This chute marks the
site of a 150-ft-long former cascade in a
surface stream of molten lava that flowed
downhill on a 10° slope. Horizontal
striations preserved on the walls of the
chute indicate places where viscous lava
was dragged against the walls. The gradient
became shallower at the northeast
end of the chute where the lava plunged
underground into what is now Tickner
Cave. Spatter on the rims of the chute
and over the roof of the cave entrance
testifies that limited fountaining of the
molten lava took place at the point where
it surged underground.
From this point Tickner Cave can be
traversed for 1,450 ft downstream. At
several places along its course molten
lava broke out onto the surface through
skylights and medial cracks along the
Figure 37. Entrance area shows stacked holes that lent name to Berthas Cupboard
Cave (see fig. 4 and map 9, pl. 3).
46 Selected Caves and Lava-Tube Systems, Lava Beds National Monument, California