Lava cascade in Thunderbolt Distributary of Labyrinth Cave system

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stream, the ceiling heights drop, the walls narrow, the tube takes on an A-frame cross section (fig. 54) like that in the Veritable Venturi beneath, and the walls have spiny pahoehoe benches 1 ft high that curb a shallow central channel. Upstream from its intersection with the Lower Entrance Tube, the tube is larger and farther upstream the floor is entirely covered with collapse debris. Ceiling heights increase markedly 50 ft upstream from the breakdown, where the remains of a filled lava tube can be seen in the roof. A steep-sided collapse pile covers the floor a little farther upstream, and the tube widens to 50 ft in the area of this collapse. The floor of the tube then descends to a low spot on the upstream side of this collapse pile, and from there a soil-covered slope leads upstream to the vertical chimney, which is the upstream exit from Post Office Cave (fig. 55). lava Transport Using average underground flow rates of 0.6-3.6 mi per hour, as determined by Peterson and Swan son ( 197 4) from observations through skylights on active lava tubes in Hawaii , the volume of lava transported in a full tube of known cross-sectional area can be calculated. Assuming these Hawaiian flow rates and the same gradient, a tube the size of the Cocoa Pipeline could transport 14-86 million cubic feet of lava per day, the lower number being comparable to typical Hawaiian eruption rates (Peterson and Swanson, 1974). At least five large lava-tube systems operated during emplacement of the basalt of Mammoth Crater, although they were probably not all active at the same time. The five are, from west to east, (1) Upper Ice Cave, (2) north of Bearpaw Butte, (3) Bearpaw-Skull, (4) Heppe-Cave Loop Road Post Office-Craig, and (5) Hidden Valley. Volume is estimated to be nearly 1.2 cubic miles covering approximately 100 square miles and spreading west and east beyond the boundaries of the monument (fig. 1). The basalt of Mammoth Crater also possesses a single remanent paleomagnetic direction, and this data suggests a very short duration , perhaps as little as a decade, for emplacement of the entire unit (Donnelly-Nolan and Champion, 1987). If 1. 2 cubic miles of basalt were emplaced in 10 years, the calculated flow rate would be 48 million cubic feet per day; this figure is slightly more than three times higher than the typical Hawaiian flow rates cited by Peterson and Swanson (1974) but within the range of Hawaiian eruption rates. If the basalt of Mammoth Crater erupted at approximately the same rate as in a typical Hawaiian eruption, 30 years may have been required for the eruption. Note that Post Office tubes transported a large volume of lava (at least some of which probably traveled through Craig Cave tube) 5 to 10 mi to the east and northeast from the east monument boundary nearly to California Highway 139. However, some of this large expanse of basalt of Mammoth Crater may have been transported by the inferred Hidden Valley tube system, which is buried by the basalt of Valentine Cave. Intermittent changes of hydraulic pressure and flow rate occur within such a tube system. Also, roof collapses that partially or completely plug flowing tubes affect the hydraulic pressure within tube systems. Pooling of lava behind an annealed flow front or a lava collapse, along with short-term fluctuations in eruptive rates, probably represented the only conditions under which any of the Post Office tubes were completely filled with lava for an extended period of time, with the possible exception of the Cocoa Pipeline. Tube-in-tubes, smooth pahoehoe benches, and the many thin accretionary linings in the tubes of Post Office Cave support this reasoning, for they record repeated periods of pooling, withdrawal, and refilling with lava. Craig Cave and Craig Temple An oval collapse trench 125 ft long and 60 ft wide provides entrances for both Craig Temple and Craig Cave. Downstream from this breakdown most of Craig Cave is nearly drained of lava; the last trickle of pahoehoe lava to occupy the tube filled only the rounded central part of the tube's floor and seldom reached the steep walls except on the outside of bends. At its downstream end the lava tube is plugged by a roof collapse. In contrast, Craig Temple, the part of the tube upstream from the breakdown, is two-thirds filled by two tongues Figure 55. Explorer emerges from narrow exit of Post Office Cave (see fig. 4 and map 15, pl. 5). Information about cave access, along with safety and exploration guidelines are obtained at Visitor Center in Lava Beds National Monument. 80 Selected Caves and Lava-Tube Systems, lava Beds National Monument, California
of lava. A late tongue of the basalt of Mammoth Crater that formed the tube advanced downstream. A tongue of the much younger basalt of Valentine Cave entered from the surface and flowed into the upstream end of the collapse trench (fig. 56); it then cascaded over the upstream slope of the collapse pile that lies at the entrance to Craig Temple. Craig Cave was named by J.D. Howard in honor of the Craig brothers, who first guided him to the cave. Some confusion exists in records at Lava Beds National Monument regarding use of the name "Craig Temple." It is reasonably certain that Howard applied this name only to the upstream continuation of the cave above the collapse trench, which he explored during a second visit. One can imagine a resemblance to a temple in the upper extension of the cave where two steeply sloping and rough-surfaced flow fronts produced a room 40 ft wide and 100 ft long, with an impressive domed roof rising above it. The extremely rough surface of huge tilted and upturned pahoehoe slabs on the flow that advanced upstream from the breakdown may be likened to pews in a cathedral. The downstream flow advanced in flow units and produced a series of altar-like steps. On map 16 (pl. 5), the name "Craig Temple" is used only for this room in upstream Craig Cave tube. However, at some time in the past, the words "Craig Temple" were painted on the rock above the entrance to Craig Cave. To add to the confusion, the pamphlet "Origin of Geographical, Geological, and Historical Features in Lava Beds National Monument and Adjacent Lands" (available at the Visitor Center) states that Craig Cave "was originally called Craig Temple." Craig Cave An impressive cavern more than 50ft wide yawns beneath a broad arch in the cave roof (fig. 57) at the downstream end of the collapse trench, which provides access to the Craig lava tube (map 16, pl. 5). In the roof of the cave, and in the north wall of the trench, are several well-defined flow units of basalt lava. Most are less than 4 ft thick and are similar to the flow units from the collapse trench at the downstream entrance to Post Office Cave. The Craig tube is probably a downstream continuation of the tube system that forms Post Office Figure 56. Frozen tongue of much later basalt of Valentine Cave (see fig. 4 and map 8, pl. 3) flowed over edge of collapse t rench that allows access to Craig Cave (left edge of photograph). Continued flow of this younger basalt would have filled Craig Cave (see fig. 4 and map 16, pl. 5) and buried trench. Craig Temple, upstream, was partly filled by the younger flow. Craig Cave and Craig Temple 81
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Lava cascade in Thunderbolt Distrib
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Frontispiece. Two visitors explore
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DEPARTMENT OF THE INTERIOR MANUEL L
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Caves easily accessible from Cave L
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PLATES [In pocket] 1. Caves of the
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Many of the feature names used in t
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Tulelake LOWER KLAMATH LAKE Prisone
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EXPLANATION ................... Lav
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flow, then the lava may pool behind
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"pull outs" where the dripping plas
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Mushpot, Catacombs, Ovis, and Merri
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Waters agreed to do the cave mappin
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into the distributary in the genera
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crawled 180 ft from the Mushpot tub
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es of plaster clog its continuation
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level of the tube. The southern ent
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surface collapse and only one comer
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dead-end passages on different vert
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and a roof covered with lavacicles
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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 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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