Environmental Geology Lecture - Karst terrains and associated environmental concerns

Features that characterize karst terranes:

Figure to left is of the sacred cenote (sinkhole) at Chichen Itza, a Mayan site on the Yucatan peninsula of Mexico. Offerings and sacrificial victims were thrown into the sinkhole which was seen as a portal to the gods of the underworld. Mayans that live in this area today continue to have their lives affected by the karst setting they live in. It provides the unique situation of a jungle without rivers or other surface water bodies, except the cenotes.

Areas in U.S. with extensive karst development:

Figure to the right is of a blue hole, a large spring, in northern Florida. This single spring creates enough flow to feed a fair sized stream, and is the surface exit of part of a large submerged cave system. The groundwater table surface is very shallow and this is a good example of a cave network under phreatic conditions.

Factors influencing bedrock solubility:

Environmental concerns associated with karst terranes:

Localization of cavernous and sinkhole development:

Caves as valuable scientific resources:

Related web sites:

This is a photo of an excavation into sediments that filled a sinkhole near Hot Springs, S. Dakota taken on the 1997 Dept. of Geography and Geology field trip to the Black Hills. The sinkhole trapped a number of young male mammoths over time among other organisms, and represents a paleontologic treasure trove of information on the environment in this area during the last Ice Age. Distinct thin laminations of sediments may represent annual deposits or storm events. This filled sinkhole is part of karst terrain that encircles the interior of the Black Hills and which is due to relatively soluble limestone formations. Jewel and Wind caves occur in these same limestone formations.

Above is a photograph taken on the same field trip of crystal studded speleothems in Jewel Cave. After 'aggressive' waters dissolved an extensive cavernous void, then saturated waters started filling in the void by precipitating calcite and other minerals and forming these cave formations. The last phase of precipitation covered the walls with crystals forms, giving Jewel Cave its semi-unique character and name. Thus, capture in cave sediments and speleothems is a history of the groundwater table levels and chemistry in the area, and this in turn is a function of climate.

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