Shelfstone in Atlantis, Lechuguilla Cave (Team B. 1991)

Becky Lauren Quinlan

Sulfuric Acid Speleogenesis

Geomorphology Seminar

May 16, 2005

History of cave formation thought

Theorists have written about their speculations of the processes of cave formation since at

least 1503 (Shaw, 2000). Theories formulated before the 20th century were divided between the

catastrophic camp and those that felt that steady processes rule speleogenesis (Shaw, 2000).

Biblical events, earth movement and cosmological theories that showed that caves were formed

with Earth’s creation were the focuses of the catastrophic group (Shaw, 2000). Others were

certain that caves could only be formed over long periods through steady processes like erosion

and dissolution (Shaw, 2000). In the early 20th century, the classic debate between vadose and

phreatic processes was subjected to the scientific method (Lowe, 2000). In his 1930 paper, The

origin of limestone caverns, William Morris Davis wrote that caves formed during very long

stretches of time by fresh water below the water table (Lowe, 2000). Davis acknowledged that

physical exploration of caves needed to be undergone, and he failed to establish models of cave

development to drive investigations into his assertions on drainage and deep phreatic dissolution

(Lowe, 2000). Others, like Swinnerton in 1929, endorsed vadose and shallow phreatic

speleogenesis (Lowe, 2000). Most of the theories proposed and developed before the 1950’s

have been further developed and accepted by geomorphologists and geologists (Lowe, 2000). In

the latter half of the 20th century, in addition to new theories of cave development like the

sulfuric acid theory, scientists began to better understand the interactions between caves and their

surroundings (White, 2000a). An emphasis was placed on the geologic setting of caves and the

chemical processes of karst dissolution (White, 2000a). Geomorphologists agreed that most

caves were formed in limestone, which was dissolved by carbonic acid and carried away, and

many researchers focused on the mechanism by which fresh, undersaturated water could reach

deep carbonate aquifers (White, 2000a). The speed of cave formation is dependant on the rate

of limestone dissolution and the rate at which fresh water can replace that already saturated with

limestone (White, 200a). The latter control is stratigraphically and hydrologically dependant

(White, 2000a). Researchers have attempted to quantify the dissolution rate of limestone, but

have been unsuccessful in agreeing on a number using field observations or lab experiments; the

rate seems to hover between about 25 and 100 micrometers per year of denudation (White,

2000b).

History of the sulfuric acid theory

Though most caves, by far, are formed through carbonic acid speleogenesis, some caves,

like Carlsbad Caverns in the Guadalupe Mountains of southeastern New Mexico, possessed

features inconsistent with the model. While working on his dissertation in the early 1970’s,

Egemeier (1973, p 9, 27) acted under the assumption that the caves in Big Horn Basin, Wyoming

formed like most other caves, aided by the heat provided by deep artesian flow (p 8-9). He

observed the odor of hydrogen sulfide (H2S) in Lower Kane Cave, an active cave in the region,

as well as the formation

of gypsum crusts and

mounds within the

caves. He also

observed the quick

dissolution of gypsum

mounds by water both

within and outside

caves, where gypsum Figure 1. Massive gypsum block in the Big Room, Carlsbad Caverns (Egemeier, 1973).

blocks had been used to dam small streams. He noted the unusual pattern of caves widening

upstream along flowing water. Also confusing to Egemeier was the fact that, despite his

assumption of caves being formed by flowing water features, he observed in the active caves no

or little incision of the flowing water into the cave floors, potholes, or meanders influencing the

shape of cave rooms (p 32). Egemeier observed phreatic features in most of the Big Horn Basin

caves, such as spongework, pockets in the walls, ceilings, and floor, bedding and joint

anastomoses and continuous rock spans (p 34-35). Egemeier proposed without evidence or

citation that he believed the gypsum was formed during speleogenesis (p 36), giving the reader a

hint of the theory to come. In his conclusions, Egemeier accumulated the evidence of H2S in the

air and gypsum crusts on the walls to propose a sulfuric acid induced enlarging of the active

caves (p 39), and boldly stated his belief that the caves of the Big Horn Basin are formed by the

replacement of limestone and dolomite by gypsum through the action of sulfuric acid (p 40).

Egemeier also suggested a phenomenal rate of enlargement 3.7 m3 of limestone removed per

year, allowing Lower Kane Cave, with a volume of 10,000 m3, to be excavated in as little as

3000 years, a process that would take much longer with carbonic acid dissolution (p 53). He

even proposed that the H2S could be derived from a number of sources, simultaneously: the

thermal springs, sulfate reducing bacteria, and the hydrocarbon reservoirs found in the same

limestone formation of the caves (p 64). He extended his replacement theory to Carlsbad

Caverns and refuted Good’s 1957 proposal that the gypsum found in the big room precipitated

from cooling gypsum-rich water, giving good evidence such as the absence of silt and sand from

the deposits, the sheer volume of gypsum deposits, and the lack of limestone blocks embedded in

the gypsum (p 69-70). Egemeier’s amazing dissertation incorporated many of the elements

present today in the sulfuric acid theory of speleogenesis, but he was not the only researcher

beginning to realize that some caves had features inconsistent with carbonic acid dissolution and

to turn to sulfur for an explanation.

In 1971, Dwight Deal, Harvey

DuChene, Carol Hill and Dave Jagnow,

four graduate students, made a visit to

Carlsbad Caverns. They began to

contemplate the unusual cave features, like

the softness of the walls, odd speleotherms

that looked like a line of popcorn (Figure

2) or a wall of corn flakes, and the huge

blocks of gypsum (Figure 3) on the floor

of some rooms (DuChene and Hill, 2000). David Jagnow chose to investigate the speleogenetic

origin of the Guadalupe Mountains caves for his masters thesis. Without knowledge of

Egemeier’s work in the Kane Caves of Wyoming, he also proposed a sulfuric acid origin for the

caves (Jagnow et al, 2000; Jagnow, 1977). Jagnow pointed out that because of Carlsbad

Caverns’ immense size and beauty, many geologists and geomorphologists have contemplated

the origin of the cave system, and had debated the origin’s vadose or phreatic nature (p 10-14).

Despite the great attention paid to the large gypsum blocks on the big room floor, no previous

Figure 2. Gypsum "popcorn" in Lechuguilla Cave (Thompson, 1991).

Figure 3. Large gypsum blocks on the floor of Prickly Ice Cube Room in Lechuguilla Cave (Team B, 1991).

study except Egemeier’s thesis of 1973 proposed an alternative speleogenetic process to carbonic

acid dissolution (Jagnow et al, 2000). Jagnow drew on the work of White in 1965 and

Morehouse and Pohl in 1968, who proposed sulfuric acid dissolution speleogenesis for caves in

Iowa and Kentucky (Jagnow, 1977, p 107). Jagnow believed that sulfuric acid dissolution was

helped along by the carbonic acid process, which he considered possibly more important in the

speleogenesis of caves in the Guadalupe Mountains (p 109). He speculated that the source of

sulfide for the sulfuric acid reactions was the extensive deposits of pyrite in the area (p 109)

possibly converted by iron bacteria (p 120), and cited the large gypsum beds and gypsum

“popcorn” on the cave walls as evidence of the caves’ sulfuric acid origin (p 119). In an

example using the Left Hand Tunnel of Carlsbad Caverns, he proposed a chronology of cave

formation: “1) solution of Left Hand Tunnel 2) deposition of clay and silt banks 3) truncation

and incrustation by gypsum crust 4) final deposition of stalactites and massive popcorn” (p119).

The theory’s time had come and others were beginning to explore the claims made by

Jagnow (1977) and Egemeier (1973). Donald Davis, in 1973 and 1979, cited and refined

Egemeier’s and Jagnow’s proposals (Jagnow et al, 2000). He stated in his 1979 paper that

sulfuric acid was more important in speleogenesis than Jagnow has surmised, and the pyrite

source was not enough to produce the volumes of sulfuric acid needed to carve the caves

(Jagnow et al, 2000). Davis also published the first review of the sulfuric acid theory and

brought together the proposals of Jagnow, Egemeier, and Queen, Palmer and Palmer, who

proposed the brine mixing mechanism for the formation of gypsum blocks, to create a working

theory for speleogenesis (Jagnow et al, 2000). The theory incorporated brine mixing of fresh,

meteoric water with phreatic sulfide brine to create sulfuric acid at the air/water interface

(Jagnow et al, 2000). Carol Hill, in 1979, provided the first real evidence for the origin of sulfur

from hydrocarbons instead of the Castile Formation as proposed by Jagnow (1977) (Jagnow et

al, 2000). She had sampled the gypsum of the Big Room of Carlsbad Caverns, and found the

sulfur to be isotopically light (δ34S = -13.90/00), where the Castile Formation sulfur averaged

much heavier (δ34S = +10.30/00) (Jagnow et al, 2000).

The 1980’s brought further refinement of the sulfuric acid speleogenesis theory with the

posthumous 1985 publication of Eigemeier’s Theory for the Origin of Carlsbad Caverns and

Carol Hill’s 1987 Geology of Carlsbad Caverns and Other Caves of the Guadalupe Mountains,

New Mexico and Texas in which she drew the connection between cave origin and sulfur

deposits in the Delaware Basin (Jagnow et al, 2000). Jagnow et al (2000) claimed that Hill’s

publication by the New Mexico Bureau of Mines and Mineral Resources showed that the sulfuric

acid theory had entered the mainstream of speleogenetic thought. With the breakthrough in 1986

into the vast expanses of Lechuguilla Cave, pristine evidence was rapidly collected that

supported the sulfuric acid theory and the 1990’s were a time of theoretical verification and

refinement of the theory (Jagnow et al, 2000).

Evidence for the theory

Polyak and Provencio (2000b) assert that, unlike carbonic acid dissolution caves, sulfuric

acid caves leave by-products of the speleogenetic process that can be studied. One of these by-

products, alunite, can be dated, which is just what Polyak and Provencio undertook in their

2000b paper. Samples of alunite were taken from Guadalupe Mountain caves at various

elevations. Testing dated the speleogenesis of caves at higher elevations (Virgin and

Cottonwood) at 11 Ma and those at lower elevations (Lechugilla, Carlsbad, and Endless) at 6, 5,

and 4 Ma. These dates correspond to the previously determined aquifer water level patterns,

affirming the theory of sulfuric acid generation and cave formation at the water table in the

Guadalupe Mountains (Polyak and Provencio, 2000b). Polyak and Provincio (2000a) did not

confine themselves to alunite, but studied all

the known and suspected by-products of

sulfuric acid speleogenesis. They divided the

by-products into primary, those formed directly

from speleogenesis, and secondary, which are

altered primary by-products. Primary by-

products are found in cave locations, which are

protected from fresh water and consist of

gypsum, elemental sulfur, hydrated halloysite,

alunite, natroalunite, jaorsite, hydrobasaluminite,

quartz, todorokite, rancieite and amorphous silica

and aluminum sulfates (Polyak and Povincio,

2000a). Gypsum is the most prevalent of the

primary by-products, and can be seen in the large

Figure 4. Gypsum glacier in the Prickly Ice Cube Room of Lechuguilla Cave (Team B, 1991).

Figure 5. Researcher rappelling through a drip-pit and airflow corrsion shaft in a 10 m thick gypsum glacier, Glacier Bay, Lechuguilla Cave (Team B, 1991).

floor blocks in Carlsbad, Lechuguilla and other caves in the Guadalupe, though gypsum may also

be a secondary by-product. Palmer, Palmer and Davis (1991) and Davis (2000) described the

gypsum mounds in Lechuguilla Cave, which include crevasse features and the calving of blocks,

as resembling ice glaciers (Figure 4) that have been observed up to 10 m in thickness (Figure 5).

Primary gypsum is also found in the form of wall and ceiling rinds (Jagnow, 1977; Polyak and

Provincio, 2000a), and the occurrence of gypsum rinds and blocks were described in Egemeier

(1973) in both active and relict caves. Another primary by-product of sulfuric acid speleogenesis

is elemental sulfur (Figure 6), which was shown by Hill in 1987, along with gypsum from the

Big Room of Carlsbad, to be of hydrocarbon

origin, due to the light isotopic properties of

the sulfur (Polyak and Provencio, 2000a).

Montmorillonite altered by sulfuric acid

during speleogenesis transforms to hydrated

halloysite, blue or white waxy nodules like

those seen in pockets of the Green Clay

Room of Carlsbad Caverns (Polyak and

Provencio, 2000a). In the same pockets as hydrated halloysite, alunite and natroalunite can often

be found (Polyak and Provencio, 2000a). Among the secondary by-products are two varieties of

moonmilk formations, gypsum and aluminite moonmilks (Polyak and Provencio, 2000a).

In addition to the by-products of cave formation, there are distinctive characteristics of

the sulfuric acid caves, themselves. These caves often cut across stratigraphic layers, ignoring

the boundaries between layers that carbonic acid caves seem to honor (Palmer and Palmer,

2000). They typically have huge rooms (Figure 7) and passages, regularly surpassing 15 m in

Figure 6. Elemental sulfur in snowy white gypsum deposits near Ghost Town in Lechuguilla Cave (Thompson, 1991).

height and width (Hill,

2000). They have large

vertical passages and

have many passages

and rooms that end

abruptly with no

fissures for the entrance

or escape of flowing

water (Hill, 2000). The

relationship between

cave entrances and the land surface seem to be

random, and have no relationship with current or past

springs or recharge paths (Hill, 2000). The continued

study of Lechuguilla Cave in the Guadalupe

Mountains has revealed unique features that may

result from sulfuric acid speleogenesis, according to

Davis (2000). Rillenkarren, deeply grooved floors

near acid pools, seem to be the result of rapid

evaporation and condensation of aggressive water.

Rillenkarren (Figure 8) commonly have been

observed on the surface of karst features, but their

subterranean appearance seems to be unique to

Figure 7. Western Borehole in Lechuguilla Cave (Team A, 1991).

Figure 8. Rillenkarren in Acide Lake Basin, East Rift, Lechuguilla Cave (Team B, 1991).

sulfuric acid caves, appearing

in Carlsbad, Kane and

Lechuguilla caves (Davis,

2000). Rimmed vents and

small hydromagnesite

bubbles, are seen in the

rooms of Lechuguilla Cave,

though the mechanisms for

their formation are not well

understood (Davis, 2000).

Unusual corrosion/deposition lines along the walls of some rooms signify long-term layering of

air (Davis, 2000). Associated with these lines are gypsum crusts, like the lines of “popcorn”

observed by the graduate students in 1971, and beautiful aragonite frostwork. Another feature

occurring only in sulfuric acid caves so far are “rusticles” (Figure 9), stalactites and columns

consisting of a core of bacterial colonies and a shell of black oxidized iron produced by the

bacteria (Davis, 2000). Peculiar subaqueous helictites (Figure 10) are formed only where small

trickles of water flow under substantial

amounts of gypsum, then dripping into pools

where the gypsum precipitates and forms

tiny strings. All of the above features

described by Davis (2000) and others

(Palmer, Palmer and Davis, 1991), as well

as the beautiful gypsum chandeliers (Figure

Figure 9. Rusticles in Lechuguilla Cave (Team B, 1991).

Figure 10. Subaqueous helictites in Sugarland, Lechuguilla Cave (Team B, 1991).

11) in Lechuguilla Cave can be considered secondary by-products of sulfuric acid speleogenesis.

Egemeier (1973) noticed the sulfur smell

of Lower Kane Cave and witnessed the

formation of gypsum rinds and gypsum mounds

in an active sulfuric acid cave in Wyoming.

Similarly, Hose and Pisarowicz (1999) have

begun to study another active sulfuric acid cave,

Cueva de Villa Luz in Tabasco, Mexico.

Though the cave had been previously studied for

its biologic features it had never been explored

from a geomorphologic perspective (Hose and

Pisarowicz, 1999). Two cavers heard a rumor of

a sulfur cave in 1987 and decided to take a look

before their flight back to the US. Pisarowicz

had never seen features like the elemental sulfur,

massive amounts of gypsum and what are now known as snottites (Figure 12). Since his first

excursion to the Cueva de Villa Luz in 1987, Pisarowicz, in the company of other researchers,

has returned a number of times to test the acidity of snottites and water drops (pH 1), sample the

levels of H2S in the air which they found to be isotopically light, as Carol Hill did for Guadalupe

caves, and to create a detailed survey of the cave. Explorers reported a sulfur smell and a

slightly thermal nature to the cave. The sulfur smell became more prevalent toward the

unvented, back portion of the cave and, when wading in the milky-white stream that runs

through the center of the cave floor, researchers noted a mild burning sensation on their feet

Figure 11. Gypsum chandeliers, Chandelier Ballroom, Lechuguilla Cave (Thompson, 1991).

(Hose and Pisarowicz, 1999). The air of the cave is toxic: carbon monoxide levels of 45 ppm,

H2S levels at 152 ppm, and O2 at a low 9% have been measured during extreme events in the

cave, and cavers left feeling ill before protective gear was adopted (Hose and Pisarowicz, 1999).

Additionally, explorers reported dead and dying bats hanging from the walls and ceilings of the

cave, though bats seem to be in residence year-round (Hose and Pisarowicz, 1999). The snottites

observed most thickly in the rear of the cave are sulfur-loving microbes that provide the

foundation of a curious food web: midges feed on the microbes, bats and fish feed on the midges,

and the local indigenous people have a traditional fishing ceremony during which they once

obtained their winter food from the sulfur-laden

stream (Hose and Pisarowicz, 1999). These

observations, and those of Lower Kane Cave,

have contributed to the current understanding of

sulfuric acid speleogenesis.

Theory as it stands

Palmer and Palmer (2000) have

explained well the current theory of

speleogenesis by a sulfuric acid mechanism in

their paper Hydrochemical interpretation of cave

patterns in the Guadalupe Mountains, New

Mexico. Palmer and Palmer (2000) reported

that the caverns seem to have formed with

complete disregard to the rock layers in which they reside. The caverns’ openings are also very

Figure 12. Snottites in Cueva de Villa Luz (PBS, 2005)

large and level in places, even though the stratigraphy lies at an angle. Palmer and Palmer

(2000) thought that indicated some control other than the lithography of the area. The current

theory is that the level rooms were formed at prehistoric water table levels where H2S in solution

and in tiny gas bubbles ascended through fissures in the bedrock until it met highly oxygenated

water and formed sulfuric acid (H2SO4). The H2SO4, with a little help from high CO2

concentrations and perhaps some help from sulfur-oxidizing bacteria to maintain low pH, then

began to enlarge the caverns at a very rapid rate, as much as 23 m3 per year (p 98). Palmer and

Palmer (2000) examined how the two essential compounds (H2S and O2 rich water) might have

come to meet. Some of the caverns were apparently formed at the water line where O2 mixing

would be expected, but some of the caverns seem to have formed deep below the water line,

which suggests that an active flow was essential in the cavern formation. In addition to the

water-line mixing that took place to create the great, level caverns, Palmer and Palmer (2000)

asserted that phreatic water must have been aggressive at depths up to 200m. They believed that

meteoric water flowing though joints may have been subjected to tectonically-induced

hydrostatic pressures that pushed the water table higher episodically.

Palmer and Palmer (2000) integrated previous studies to support their explanation for the

mixing necessary for sulfuric acid speleogenesis. They turned to Carol Hill (1996) for a detailed

description of the stratigraphy and geology of the Guadalupe Mountains, Polyak and Provencio

(2000b) to provide the dating of speleogenesis of particular caves, and Egemeier (1973) and

others for observations of H2S associated with similar cave features. Also, Palmer and Palmer

(2000) described in detail the replacement of limestone and dolomite by gypsum and the

formation of the great gypsum blocks as in-situ replacement instead of falling speleotherm

accumulation speculated upon by Egemeier (1973). In addition to clarifying the chemical and

physical mechanisms for sulfuric acid speleogenesis, the Palmers acceded that not all is

understood and further research is necessary to better understand the process. They felt that

more complete mapping of the Guadalupe caves might aid correlation of water table-formed

rooms. It is now understood that the Guadalupe caves formed from a combination of phreatic

and vadose processes; water from above combined with H2S-rich water from below caused the

rapid dissolution and replacement of limestone and dolomite. Vadose flow removed much of the

resulting gypsum and created many of the speleotherms seen in the caves today. Palmer and

Palmer (2000) asserted that further distinctions between vadose and phreatic speleogenetic

mechanisms are still needed.

Conclusion

Now that the sulfuric acid speleogenesis theory has gained acceptance and the evidence

for cave development by the sulfuric acid mechanism is becoming well defined, more cave

systems are joining the speleogenetic ranks of the Guadalupe Mountains caves and those of the

Big Horn Mountains in Wyoming. Other caves known or suspected to have been formed

through sulfuric acid speleogenesis are Fiume-Vento Cave in Italy, La Cueva de Villa Luz,

Mexico (active), Las Brujas Cave in Argentina, Kugitangtou caves of Turkmenistan, Redwall

caves, Grand Canyon, Arizona, Movile Cave, Romania(active), and Mbobo Mkulu Cave, South

Africa (Jagnow et al, 2000). Researchers continue to explore sulfuric acid caves, mapping,

testing ad photographing their new discoveries and aiding the consolidation and development of

the theory.

Sources

Davis, Donald G. 2000. Extraordinary features of Lechuguilla Cave, Guadalupe Mountains, New Mexico. Journal of Cave and Karst Studies, 62(2): 147-157.

DuChene, Harvey R. and Carol A. Hill. 2000. Introduction to the caves of the Guadalupe

Mountains Symposium. Journal of Cave and Karst Studies, 62(2): 53. Eigemeier, Stephen J. 1973. Cavern Development by Thermal Waters With a Possible Bearing

on Ore Deposition. PhD Dissertation. Stanford University. Hill, Carol. 1996. Geology of the Delaware Basin, Guadalupe, Apache, and Glass Mountains,

New Mexico and West Texas. Albuquerque: Society for Sediment Geology, Permian Basin Section.

Hill, Carol. 2000. Overview of the geologic history of cave development in the Guadalupe

Mountains, New Mexico. Journal of Cave and Karst Studies 62(2): 60-71. Hose, Louise D. and James A. Pisarowicz. 1999. Cueva de Villa Luz, Tabasco, Mexico:

Reconnaissance study of an active sulfur spring cave and ecosystem. Journal of Cave and Karst Studies, 61(1): 13-21.

Jagnow, David H., Carol A. Hill, Donald G. Davis, Harvey R. DuChene, Kimberly I.

Cunningham, Diana E. Northup, J. Michael Queen. 2000. History of the sulfuric acid theory of speleogenesis in the Guadalupe Mountains, New Mexico. Journal of Cave and Karst Studies, 62(2): 54-59.

Jagnow, David H. 1977. Geologic Factors Influencing Speleogenesis in the Capitan Reef

Complex, New Mexico and Texas. Masters Thesis. Albuquerque: University of New Mexico.

Lowe, David J. 2000. Development of speleogenetic ideas in the 20th century: the early modern

approach. In Speleogenesis: Evolution of Karst Aquifers. Alexander B. Klimchouk, Derek C. Ford, Arthur N. Palmer, Wolfgang Dreybrodt, Eds. Huntsville, Alabama: National Speleological Society, Inc. 30-38.

Palmer, Arthur N., Margaret V. Palmer, and Donald G. Davis. 1991. Geology and origin of

Lechuguilla Cave. In Lechuguilla: Jewel of the Underground. Michael Ray Taylor (Ed.) Basel, Switzerland: Caving Publications International. 22-31.

Palmer, Arthur N. and Margaret V. Palmer. 2000. Hydrochemical interpretation of cave

patterns in the Guadalupe Mountains, New Mexico. Journal of Cave and Karst Studies, 62(2): 91-108.

PBS. 2005. Snottites. Available online [www.nps.gov/wica/PBS/Special_Evening_Program.htm]. Last accessed: May 3, 2005.

Polyak, Victor J. and Paula P. Provencio. 2000a. By-product materials related to H2S-H2SO4

influenced speleogenesis of Carlsbad, Lechuguilla, and other caves of the Guadalupe Moutains, New Mexico. Journal of Cave and Karst Studies, 63(1): 23-32.

Polyak, Victor J. and Paula P. Provencio. 2000b. Summary of the timing of sulfuric-acid

speleogenesis for Guadalupe caves based on ages of alunite. Journal of Cave and Karst Studies, 62(2): 72-74.

Shaw, Trevor R. 2000. Views on cave formation before 1900. In Speleogenesis: Evolution of

Karst Aquifers. Alexander B. Klimchouk, Derek C. Ford, Arthur N. Palmer, Wolfgang Dreybrodt, Eds. Huntsville, Alabama: National Speleological Society, Inc. 21-29.

Team A. 1991. Photographs. In Lechuguilla: Jewel of the Underground. Michael Ray Taylor

(Ed.) Basel, Switzerland: Caving Publications International. Team B. 1991. Photographs. In Lechuguilla: Jewel of the Underground. Michael Ray Taylor

(Ed.) Basel, Switzerland: Caving Publications International. Thompson, Norman R. 1991. Photographs. In Lechuguilla: Jewel of the Underground. Michael

Ray Taylor (Ed.) Basel, Switzerland: Caving Publications International. White, William B. 2000a. Development of speleogenetic ideas in the 20th century: the modern

period, 1957 to the present. In Speleogenesis: Evolution of Karst Aquifers. Alexander B. Klimchouk, Derek C. Ford, Arthur N. Palmer, Wolfgang Dreybrodt, Eds. Huntsville, Alabama: National Speleological Society, Inc. 39-43.

White, William B. 2000b. Dissolution of limestone from field observations. In Speleogenesis: Evolution of Karst Aquifers. Alexander B. Klimchouk, Derek C. Ford, Arthur N. Palmer, Wolfgang Dreybrodt, Eds. Huntsville, Alabama: National Speleological Society, Inc. 149-155.