LEARN Lechuguilla Expedition
by Donald Davis

The expedition was successful, with about 5,978 feet surveyed, bringing Lechuguilla Cave to more than 90 miles. The mapping, however, was essentially mop-up of breakdown and maze in known areas, with no significant breakaway from the existing pattern. Some interesting geological and speleogenetic observations were made.

Ron DeLano acted as camp manager, and Steve Koehler provided line plots for in-cave use. The expedition had been authorized to have 12 people, but four had cancelled, and only two replacements were found in time, so there were ten cavers divided into three teams. These and their survey results were as follows:

Steve Koehler, Ron DeLano, Eirik Fowler	SW Branch, 2732'
Tom Livingstone, Rob Mauceli, James Lawton, Chuck Cummings	SW Branch, 996'
Dave Jones, Peter Bosted, Donald Davis	Far West, 2250'

The Southwestern teams worked in several areas including the Void complex, Land of Awes, High Hopes, and Deliverance Passage (finding no unsurveyed passage in the latter). I lack details of the activities in the SW Branch. The Land of Awes team noted that the Bitter Water Pool is now only about two feet long and two inches deep-down from 6 by 4 feet and 6 inches deep when it was discovered. At this rate it will disappear before long.

The Far West team first (Apr. 27th) surveyed breakdown/ boneyard almost beneath the camp at EY95. Apr. 28th we devoted to doing climbing leads off EKC in the Beard Room area of the passage running W from the second pit in the Northwest Passage. The more easterly went only 30 feet; the more westerly went up more than 100 feet but eventually pinched. Apr. 29th we pushed the N boundary of the complex below the Jackpot area in the EMC survey vicinity, but found no significant new passage. Apr. 30th Dave Jones led a climb into a fissure directly above directional aragonite in the entrance to the Mirage Room. This turned out to connect to an earlier survey done by Jones, Lyle Moss et al. from an approach further into the room; fissure passage continues above but is tight and unpleasant. May 1st we ascended into Southern Climes and surveyed some boneyard below the Rock 'n Rillen Room, extending the EYKH survey, then rechecked Wahoo Pit/Romper Room without finding new extensions, and finally surveyed the unsurveyed segments of the Southern Climes rope route. May 2nd we searched unsuccessfully along the N side of the Keel Haul/Long Haul branch, then mapped a minor maze underneath large rocks beneath the S side of the Long Haul near its rise into the Rainbow Room.

MINERALOGICAL OBSERVATIONS
Several interesting mineralogical features were observed in and below the Rock 'n Rillen Room in Southern Climes. Near station EYKH14A is an overhang beneath which grows a display of apparent hydromagnesite trees up to two or more inches long. These resemble aragonite bushes in growth pattern, but are thickened (up to 1/8 inch), chalky, nodular, and often twisted. Somewhat similar trees have been seen in the Far East in Boundary Waters. They are associated with krinkle blisters in both cases. They are interesting because hydromagnesite very rarely assumes tree-like forms. These new ones may shed light on the origin: this display also includes very fine aragonite needles, some of which are partly overgrown by hydromagnesite. The ones which appear to be pure hydromagnesite may have developed originally as aragonite needles which have been entirely overgrown by hydromagnesite. The nodular, curvy, twisting effect may result from irregular interstitial accumulation of fine-grained hydromagnesite deforming the original straight aragonite core. Dave Jones had earlier seen a very fine needle, several inches long, which he believes to be a selenite hair also partly overgrown by hydromagnesite. This is somewhere lower in the maze beneath the Rock 'n Rillen Room, and was not relocated on this trip. Since both minerals are evaporitic, this association, though unusual, seems feasible.

A few yards in front of this display is a breakdown piece on the right end of which is a radiating two-inch hydromagnesite tree. At the base of this, and on the tree itself, are tiny lemon-yellow crystals, presumably tyuyamunite. Peter Bosted took photos to document all of these features. We also flagged them with red- and-white tape.

Two feet from EYKH29 (mismarked EYKG29), in the maze below, is a floor patch about an inch wide of bright green material on gypsum. This may be another example of fluorapatite, the phosphate mineral originally seen in the Blanca Navidad Room. It could also be an unidentified chromium-rich substance identified by Harvey DuChene elsewhere in the cave--or something different.

Our team also undertook to measure the actual length of the soda straw stalactite near the N wall of Huapache Highway at the top of the decorated area above the Oasis Pool. I had originally estimated that this might be more than 20 feet long. The measured length (by triangulation with Suunto compass) is almost exactly 17 feet.

SPELEOGENETIC FEATURES
In an alcove along the north side of the Keel Haul/Long Haul transition, from about stations RIB15-RIB18, Dave Jones recognized a notable speleogenetic feature: a pair of major horizontal solution undercuts, separated by three vertical feet, incised into the bedrock. In many caves, these could be assumed to be differential solution along bedding planes. Here, in the massive Capitan, there is no horizontal bedding, and it is clear that they were created by enhanced solution at a water level during enlargement of the cave. They are related to the "acid lake basins" previously noted in the Southwestern and Eastern Branches, but extend widely along the passage walls, not being limited to a restricted, localized hollow. The upper undercut appears to define the ceiling of about 30 feet of the inner part of the alcove, and two subsidiary passage segments associated with it. As the level is followed out into the main passage, the undercut diminishes to two to three feet or less. The level three feet below is less well developed. Further west in Keel Haul, near IBA7 below the Rainbow Room ascent, are similar nips encircling the passage. These are at approximately the same elevation as those in the RIB survey, and may be another expression of the same aggressive water level, several hundred feet away.

I also noted related smaller-scale features near EKC7 near the Beard Room along the passage complex W from the second pit in the Northwest Passage. These are much smaller incised water lines, no more than an inch high and deep. They are somewhat discontinuous and are little more than distinctly horizontal chains of the small wall pockmarks that characterize many Capitan bedrock walls. I believe that I have seen such small-scale incised waterlines elsewhere in the cave, but they are so subtle that they are often difficult to distinguish from illusions caused by random lineups of pockets. These waterlines, on both scales, are probably evidence of hydrogen sulfide oxidation at the water table during solution of the cave voids.

LAKE LEVELS IN THE ENTRANCE SERIES, AND LAKE LOUISE
While entering April 27th, I recorded the levels of the first pool in the entrance passage, and of Lake Lechuguilla, reading the rulers put in by the Park. The first pool had risen several inches overnight, since Ron DeLano had recorded it. This was evidently in response to the steady rain of the previous two days. On our exit May 3rd, it was down 3/4 inch. Lake Lechuguilla, on the other hand, had dropped since it was last read. It dropped another 3/4 inch during the week we were in the cave. It is now only a remnant in the bottom of its basin.

En route down into it, I looked closely at the system of cracks that crisscross the basin walls above the water. Some of these are outlined by 1/4-inch welts of moist, soft material that is apparently an evaporite deposit from evaporation of water seeping from behind the wall. This tends to confirm the speculation I had previously made: the reason that Lake Lechuguilla has declined since its discovery is probably that its basin's inner wall is a thin shell of calcite backed by a silt deposit. I surmise that greater temperature variations since the entrance was dug open have made cracks in the wall open and/or widen, allowing water to leak into the silt and to evaporate from the cracks. Thus the lake will probably never hold water as well as it did before the breakthrough into inner Lechuguilla. Fortunately, this particular vulnerability apparently does not apply to any other lake in the cave.

We also read the level of Lake Louise, which had risen a fraction of an inch in the past year that had seen less use of it. It is encouraging to see that it does have some recharge and is not irreversibly lowering.

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