Speleology

Speleology is the scientific study of caves and other karst features, their make-up, structure, physical properties, history, life forms, and the processes by which they form (speleogenesis) and change over time (speleomorphology). The term "speleology" is also sometimes applied to the recreational activity of exploring caves, but this is more properly known as caving, spelunking or potholing. Speleology and caving are often connected, as the physical skills required for "in situ" study are the same.

Speleology is a cross-disciplinary field that combines the knowledge of chemistry, biology, geology, physics, meteorology and cartography to develop portraits of caves as complex, evolving systems.

History

Prior to the mid-nineteenth century the scientific value of caves was considered only in its contribution to other branches of science, and cave studies were considered part of the larger disciplines of geography, geology or archaeology. Very little cave-specific study was undertaken prior to the work of Édouard-Alfred Martel (1859 - 1938), the 'father of modern speleology', who through his extensive and well-publicised cave explorations introduced the concept of speleology as a distinct area of study. In 1895 Martel founded the Société de Spéléologie, the first organization devoted to cave science in the world.

The growth of speleology is directly linked with that of the sport of caving, both because of the stimulation of public interest and awareness, and the fact that most speleological field-work has been conducted by sport cavers.

Cave geology and hydrology

Geochemistry speleothems

Cave cartography

The creation of an accurate, detailed map is one of the most common technical activities undertaken within a cave. Cave maps, called "surveys", can be used to compare caves to each other by length, depth and volume, may reveal clues on speleogenesis, provide a spatial reference for further scientific study, and assist visitors with route-finding.

A survey team begins at a fixed point (such as the cave entrance) and measures a series of consecutive line-of-sight measurements between stations. These measurements include direction (azimuth) taken with a compass, inclination from horizontal (dip) taken with a clinometer, and distance measured with a low-stretch tape or laser rangefinder. Coincident with recording straight-line data, details of passage dimensions, shape, gradual or sudden changes in elevation, the presence or absence of still or flowing water, and material on the floor are recorded. Later, the cartographer presents the technical measurements as a "line-plot", then draws details around the line-plot for a completed cave survey. Cave surveys drawn on paper are often presented in two-dimensional "plan" or "profile" views, while computer surveys may simulate three dimensions. Although primarily designed to be functional, some cavers consider cave surveys as an art form. The accuracy, or "grade", of a cave survey is dependent on the methodology of measurement. A common survey grading system is that created by the British Cave Research Association in the 1960s, which ranges from Grade One (a simple sketch based on memory) to Grade Six (use of tripod-mounted instruments and a temperature-calibrated steel tape), with the most common grade being Five. A BCRA Grade 5 survey utilizes hand held instruments taking measurements within one degree accuracy or better and a tape measure accurate to ten centimeters or better, per station. The equipment used to undertake a cave survey continues to improve. The use of computers, inertia systems, and electronic distance finders has been proposed, but no practical underground applications have evolved at present.

urvey error detection

Faulty instruments, imprecise measurements, recording errors or other factors may result in an inaccurate survey, although these errors are often difficult to detect. Some cave surveyors measure each station twice, recording a "back-sight" to the previous station but in the opposite direction. A back-sight compass reading that is different by 180 degrees and a clinometer reading that is the same value but with the reverse direction (positive rather than negative, for example) indicates that the original measurement was accurate.

When a loop within a cave is surveyed back to its starting point, the resulting line-plot should also form a closed loop. Any gap between the first and last stations is called a "loop-closure error". If no single error is apparent, one may assume the loop-closure error is due to cumulative inaccuracies, and cave survey software can 'close the loop' by averaging errors throughout the loop stations. Loops to test survey accuracy may also be made by surveying across the surface between entrances to the same cave.

The use of a low-frequency cave radio can also verify survey accuracy. A receiving unit on the surface can pinpoint the depth and location of a transmitter in a cave passage by measurement of the geometry of its radio waves. A survey over the surface from the receiver back to the cave entrance forms an artificial loop with the underground survey, whose loop-closure error can then be determined.

In the past, cavers were reluctant to redraw complex cave maps after detecting survey errors. Today, computer cartography can automatically redraw cave maps after data has been corrected.

Cave biology

Caves provide a home for many unique biota. Cave ecologies are very diverse, and not sharply distinct from surface habitats. Generally however, the deeper the cave becomes, the more rarefied the ecology.

Cave environments fall into three general categories:

*Endogean:the parts of caves that are in communication with surface soils through cracks and rock seams, groundwater seepage, and root protrusion.
*Parahypogean:the threshold regions near cave mouths that extend to the last penetration of sunlight.
*Hypogean:or "true" cave environments. These can be in regular contact with the surface via wind and underground rivers, or the migration of animals, or can be almost entirely isolated. Deep hypogean environments can host autonomous ecologies whose primary source of energy is not sunlight, but chemical energy liberated from limestone and other minerals by chemoautotrophic bacteria.

Cave organisms fall into three basic classes:

There are also so-called "accidental trogloxenes" which are surface organisms that enter caves for no survival reason. Some may even be "troglophobes" (“cave haters”), which cannot survive in caves for any extended period. Examples include deer which fell through a sinkhole, frogs swept into a cave by a flash flood, etc.

The two factors that limit cave ecologies are generally energy and nutrients. To some degree moisture is always available in actively-forming Karst caves. Cut off from the sunlight and steady deposition of plant detritus, caves are poor habitats in comparison with wet areas on the surface. The majority of energy in cave environments comes from the surplus of the ecosystems outside. One major source of energy and nutrients in caves is dung from "trogloxenes", the majority of which is deposited by bats. Other sources are mentioned above. [ Dr. Paul Richter, "Classifications of Cave Biota & Cave Environments" (1996)]

Cave ecosystems are very fragile. Because of their rarity and position in the ecosystem they are threatened by a large number of human activities. Dam construction, limestone quarrying, water pollution and logging are just some of the disasters that can devastate or destroy underground biological communities. [National Speleological Society, "The Fragile Underground"]

Other areas of cave science

Speleologists also work with archaeologists in studying underground ruins, tunnels, sewers and aqueducts, such as the various inlets and outlets of the Cloaca Maxima in Rome. [http://www7.nationalgeographic.com/ngm/0607/feature3/index.html]

References

External links

* [http://www.goodearthgraphics.com/virtcave/index.html The Virtual Cave: an online guide to speleothems]
* [http://www.cave-biology.org cave-biology.org] Cave biology (biospeleology) in India.