Lava cascade in Thunderbolt Distributary of Labyrinth Cave system

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level of the tube. The southern entrance of Stinking Cave shows approximately how much the cave passage has collapsed laterally. The main tube is a fairly uniform 9ft wide until it approaches the Stinking Cave collapse, where it flares to a width of 39 ft. Many thin linings of lava can be seen in the alcoves just inside the entrance arch; progressive collapse of these shells resulted in the very wide entrance arch. Labyrinth Cave System The line of collapse trenches (or breakdowns) along which Indian Well and Sentinel Cave lie intersects the Cave Loop Road area (fig. 14) at Natural Bridge and continues northeast past Ovis Cave for 2,100 ft. There, the tube that collapsed to form the collapse trenches divides into two major distributaries. Looking downstream, the one on the right appears to be the larger of the two. It extends northeast and is marked by an almost continuous line of collapse trenches for 1,250 ft. Farther northeast, a few large segments of its roof survive along a continuing line of trenches. Sentinel Cave, which consists of at least three partially collapsed feeder tubes stacked one on top of another, is a roofed-over section of this distributary system. Indian Well is the next cave that interrupts the line of breakdowns to the northeast. The left and smaller distributary (which divides into the Labyrinth Cave system) takes off on a more northerly course. Unlike the Sentinel distributary, additional distributaries diverge from it. By the time this northern line of collapse trenches, natural bridges, and partly collapsed caves reaches the northern end of the Garden Bridges area 900 ft downstream from its junction with the Sentinel distributary, it has subdivided into six major distributaries. Most of these branches, however, maintain connections with their neighbors through secondary distributaries and crossovers (see fig. 14 and map 2, pl. 1). Nearly all this network of lava tubes lies close to the surface and many roof collapse openings provide additional entrances. To the early explorers who lacked maps, these interconnected but outward-fanning underground passages seemed a complicated maze, although in reality they form an orderly distributary pattern. It is not surprising that the name "Labyrinth Caves" appears in the notes of J.D. Howard, who explored and measured the length of many Labyrinth passages between 1918 and 1933. Some of the Labyrinth System caves, however, were known to Native Americans and early settlers long before Howard's work. E.L. Hopkins explored Chocolate Cave in 1892 and named it for the chocolate-colored "mud," which coats roof and walls of parts of this cave during the period of snowmelt or after heavy rains. Other names in common use for parts of this system are Blue Grotto, Garden Bridges, Golden Dome, Hopkins Chocolate Cave (also called Hopkins Chocolate Cup), and Thunderbolt. Lava Brook, Mushpot, and Arch are the Labyrinth tubes that reach farthest northeast before filling with lava. These names and the features to which they apply are shown on figure 14 and maps 1 and 2 (pl. 1). The Garden Bridges is an area of collapse trenches and natural bridges from which the Hopkins Chocolate Cave and Golden Dome Distributaries split and fan out to the north. The true Labyrinth area lies east of Garden Bridges where the name Labyrinth is used in a more restricted sense for the maze of interconnected tubes on different levels. Finally, two very long distributaries (Thunderbolt and Labyrinth), which carried a small part of the reunited lava flood northeast into the Mushpot-Lava Brook Arch Cave area, complete the Labyrinth distributary system. The divergence of the main Labyrinth feeder into six large branches lies within an area only 650 ft long and 150 ft wide. From here the tubes fan out to the north and northeast (fig. 14). The tube in Arch Cave that is filled with lava (see northeast part of map 1, pl. 1) can be traced south and southwest through the Thunderbolt Distributary (map 2, pl. 1) and into the Labyrinth, a distance of more than 3, 800 ft. Most tubes of the Labyrinth, however, are inaccessible due to lava filling and collapse over short distances. Garden Bridges Area The name "Garden Bridges" (map 2, pl. 1) is applied to the region characterized by many large oval breakdowns separated by natural bridges, within which the original Labyrinth parent tube subdivided into six main tubes and several minor ones (fig. 21). During the time since lava drained from these tubes, the weak roof above most of the junctions, as well as above wide parts of the tubes, has collapsed. The result is many large oval collapse pits between short stretches of lava tube forming natural bridges. At the ends of some collapse pits, debris has piled up to ground level. Between such pits natural bridges probably exist, but entrance to them is blocked by talus. Many, however, are open; a climb over a loose pile of talus will generally reveal an entrance to a short section of lava tube. Geologically, most of these short sections show only a few primary features because their floors are littered with collapse blocks, and their roofs are scarred in places where blocks have fallen out. To a biologist, however, the Garden Bridges area is of much more interest. The small caves under natural bridges, the loose piles of talus blocks, and the countless nooks and crannies in the cave roof and walls provide refuge for many mammals. Birds are abundant, and there is a greater variety of insects and arachnids here than in most areas of the monument. Lizards and snakes, too, are attracted to this area by the abundance of food. Botanists, too, will find a wide variety of plant life. The large range of temperature and humidity, from the cool moist air of the caves to the burning heat and desiccation on top of the lava bridges, produces microclimates to which a surprising variety of plants has adapted. Access to the Garden Bridges is from a parking lot off the Cave Loop Road, with signs marked for both Garden Bridges and Hopkins Chocolate Cave. The trail from the parking lot forks: the left (north) fork goes to a stairway that leads into Hopkins Chocolate lava tube; the right (south) branch continues on the 20 Selected Caves and Lava-Tube Systems, Lava Beds National Monument, California
surface for 200 ft and loops back to the parking lot on a different course. This trail affords excellent views of many of the natural bridges and good opportunities to observe the varied flora and fauna. One geologic curiosity in the Garden Bridges area, a well-preserved tubein-tube (fig. 22), is easily reached from this trail. The locality is inside the remnant of a near-surface cave 120 ft long that lies in the northwesternmost line of large collapse trenches within the Garden Bridges area (labeled "tube-intube" on left edge of map 2, pl. 1). After lava had congealed on the floor of this distributary, a new surge of lava spilled along a gutter-like trough near its west wall. After solidifying a few inches along its top, walls, and floor, molten lava remaining in the interior of the new lava flow drained out and left behind an open culvert-like tube-in-tube. Small collapses allow one to peer into the tube-in-tube and see that it has its own lavacicles and dripstone walls. Upstream and downstream continuations of both tubes are hidden under collapse debris. Blue Grotto Area The area from Blue Grotto to the large collapse pits west of the Blue Grotto entrance incorporates the southern part of the Garden Bridges (map 2, pl. 1). The Blue Grotto entrance heads the only developed access trail into the complicated and extensive cave system between Garden Bridges and the two southeastern distributaries. It also provides access to the easternmost distributaries and, of course, Blue Grotto. A sign and parking lot alongside the Cave Loop Road a short distance south of the Garden Bridges parking lot marks the beginning of a trail to the Blue Grotto entrance. Underground access is provided by a stairway in a deep collapse pit in the roof of this first distributary to leave the main Labyrinth feeder; this is the longest of the distributaries (Labyrinth Distributary, map 2, pl. 1). Part of the distributary connects the Blue Grotto entrance staircase with the large collapse 110 ft upstream. This breakdown occurred at the junction where two distributaries separated and effectively blocked the upstream continuation of the distributary. Its position can be inferred from the map. It appears that the tube holding the Blue Grotto entrance departed from its northerly flowing companion in a lava cascade. Details are not clear at the head of the passage because rubble has spread into the cave from the Figure 21. Lava flow cascade in smaller tube, Garden Bridges area of Labyrinth Cave (see fig. 14 and map 2, pl. 1). ~.} . . _ ... ~ ....... . 0 3 FEET Figure 22. Sketch of tube-in-tube, Garden Bridges area (see map 2, pl. 1). After the larger tube drained, a new gush of molten lava built a small tube within the older, larger tube. Labyrinth Cave System 21
Page 2 and 3: Lava cascade in Thunderbolt Distrib
Page 4 and 5: Frontispiece. Two visitors explore
Page 6 and 7: DEPARTMENT OF THE INTERIOR MANUEL L
Page 8 and 9: Caves easily accessible from Cave L
Page 10 and 11: PLATES [In pocket] 1. Caves of the
Page 12 and 13: Many of the feature names used in t
Page 14 and 15: Tulelake LOWER KLAMATH LAKE Prisone
Page 16 and 17: EXPLANATION ................... Lav
Page 18 and 19: flow, then the lava may pool behind
Page 20 and 21: "pull outs" where the dripping plas
Page 22 and 23: Mushpot, Catacombs, Ovis, and Merri
Page 24 and 25: Waters agreed to do the cave mappin
Page 26 and 27: into the distributary in the genera
Page 28 and 29: crawled 180 ft from the Mushpot tub
Page 30 and 31: es of plaster clog its continuation
Page 34 and 35: surface collapse and only one comer
Page 36 and 37: dead-end passages on different vert
Page 38 and 39: and a roof covered with lavacicles
Page 40 and 41: puzzles abound in the Catacombs; do
Page 42 and 43: Ovis Cave Apparently, E.L. Hopkins
Page 44 and 45: thus forms a bridge over the broken
Page 46 and 47: pit is located along the southwest
Page 48 and 49: lava tubes, and the upper parts of
Page 50 and 51: occupies the lava pool just upstrea
Page 52 and 53: underway. Collapse to the surface h
Page 54 and 55: one located just below ceiling heig
Page 56 and 57: high, but it immediately widens to
Page 58 and 59: low depths along fissures. Many sma
Page 60 and 61: collapse (map 9, pl. 3). Two others
Page 62 and 63: For a short distance below the coll
Page 64 and 65: circle the two large downstream pil
Page 66 and 67: where it opens into the north end o
Page 68 and 69: water well, the cave changes marked
Page 70 and 71: the older Schonchin Butte lava flow
Page 72 and 73: here to the entrance, the tube is f
Page 74 and 75: One cannot walk beneath it, as unde
Page 76 and 77: Room-is actually a natural bridge,
Page 78 and 79: pooled in the mouth ofthe tributary
Page 80 and 81: perfection and cleanliness of its l
Page 82 and 83:
etween the benches. The levees are
Page 84 and 85:
tubes created a cave floor that is
Page 86 and 87:
cessive accretionary linings of lav
Page 88 and 89:
two levels were joined by a breakdo
Page 90 and 91:
ft and passes through several level
Page 92 and 93:
stream, the ceiling heights drop, t
Page 94 and 95:
Cave. Collapse rubble half fills Cr
Page 96 and 97:
heights are between 12 and 20 ft in
Page 98 and 99:
Blue Glacier Room, where continuati
Page 100 and 101:
upstream from the one noted by the
Page 102 and 103:
Red Ice Room (fig. 63), which lies
Page 104 and 105:
tation that this tube system was fe
Page 106 and 107:
sured ground now occupies nearly tw
Page 108 and 109:
The larger and more interesting cav
Page 110 and 111:
part talus was reversed. Moreover,
Page 112 and 113:
long and 300ft in maximum width. Th
Page 114:
and lunar implications: Communicati
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Lava cascade in Thunderbolt Distributary of Labyrinth Cave system

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