Students with physical disabilities encounter challenges in any scientific discipline, yet the geosciences have extremely low participation levels for persons with disabilities. Because of the emphasis placed on field research at the undergraduate level, persons with mobility impairments face limited opportunities for progressing in the geosciences. One strategy to address this is the application of adaptive technologies, such as virtual field trips (VFTs), as a supplement to traditional field instruction. A common goal of VFTs and other adaptive technologies is to promote equal access to undergraduate geoscience curricula for physically impaired students. If the scientific talents of these students are embraced and accommodated, regardless of their physical ability, the overall welfare of the geosciences as a discipline is enhanced. This paper describes ongoing research into the development of one specific VFT: an electronic re-creation of Mammoth Cave National Park for the Introduction to Cave and Karst Systems field course at a Midwestern research university. This paper focuses on the theoretical processes necessary to conduct qualitative inquiry for the purpose of developing an accessible, alternative field-based learning environment. Grounded theory and critical theory are contrasted as two possible guiding frameworks. Three roles for the researcher are compared: researcher-as-observer, participant-researcher, and action-researcher. Phenomenology is discussed as the preferred methodological choice for this research, and attendant methods are described. Finally, a discussion of validity and reliability issues is provided. This paper is intended to serve as a guide for future researchers embarking on qualitative studies similar to this one.

Multiple cosmogenic nuclides with different decay rates can be used to date exposure and burial of rocks over the timescales of radioactive decay. This paper reviews the development of such dating methods over the past ∼50 years, beginning with a historical perspective on early meteorite studies, and later focusing on recent examples in the terrestrial field using the 26 Al- 10 Be pair in quartz. Two classes of terrestrial applications are discussed in detail. The first involves the use of 26 Al and 10 Be in rock or sediment that has experienced a complex history of repeated exposure and burial. In these cases, the cosmogenic nuclides can only provide a minimum near-surface age. Examples include sediment from beneath desert sand dunes, and rocks from beneath cold-based glaciers. The second class of application uses 26 Al and 10 Be to date discrete burial events, in cases where sediment has experienced a simple history of exposure followed by rapid burial. Examples include cave sediments, alluvial deposits, and sediment buried beneath glacial till. Finally, the half-lives of 26 Al and 10 Be are discussed, with special attention given to discrepant estimates of the 10 Be half-life. It is shown that geologic data are consistent with either half-life estimate of 1.51 m.y. or 1.34 m.y., but more closely conform to the shorter half-life.

Rivers across unglaciated portions of the Appalachian Plateaus of Tennessee and Kentucky are deeply entrenched, almost without exception. Widespread gravel deposits on upland surfaces, combined with broad straths and terraces inset beneath the highlands indicate a history of base-level stability punctuated by periods of river incision. Determining the exact timing of episodic incision historically has been difficult due to a combination of unsuitable dating methods and poorly preserved surface materials. Recently, advances in analytical techniques have allowed researchers to constrain the incision history by utilizing the hydrologic link between multilevel cave systems and regional rivers. In this study, we date clastic sediments deposited in caves associated with the Cumberland River using cosmogenic 26 Al and 10 Be, and show that they correspond to: (1) deposition of upland (Lafayette-type) gravels between ca. 5.6 Ma and ca. 3.5 Ma; (2) initial incision of regional rivers into the Highland Rim after ca. 3.5 Ma; (3) development of the Parker strath during the interval between ca. 3.5 Ma and ca. 2 Ma; (4) incision of the Parker strath at ca. 2 Ma; (5) shorter cycles of incision after ca. 1.3 Ma associated with terraces above the modern floodplain; and (6) regional aggradation at ca. 0.8 Ma. Burial ages of cave sediments record more than 5 m.y. of incision history within the unglaciated Appalachian plateaus and constrain the time needed to develop multilevel cave systems on plateau margins.

The central questions of karst hydrology concern (1) recharge, storage, and flow of groundwater in contemporary aquifers, (2) identification of geologic constraints on groundwater storage and flow paths, and (3) understanding of how aquifers evolve through time and the relation of this evolution to the evolution of interconnected surface-water basins. Karst aquifers generally display matrix, fracture, and conduit permeability with contrasts in effective hydraulic conductivity of many orders of magnitude. Dispersed recharge into the matrix and fracture permeability provides most of the storage and a slow-response flow system, while point recharge into the conduit system provides quick flow and little storage. A current question is how to describe these components of permeability and the interchange of groundwater between them. Groundwater basins can be delineated by tracer studies and geologic boundary conditions. Progress is being made on the quantitative, fluid mechanics description of conduit flow. The evolution of karst aquifers is a mainly chemical process, with some transport of insoluble clastics by high-velocity conduit waters. The equilibrium carbonate chemistry has been well established for a long time, including accurate values for equilibrium constants. Conduits, shafts, and solutionally modified fractures are the result of differential dissolution rates. Geochemically satisfactory descriptions of dissolution kinetics have been established, so that the evolution of karst aquifers through time can be accurately described. Overall, a comprehensive model for karst aquifer behavior seems to be within sight.