Browsing by Subject "Cave"
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Item A Hydrological Model of Harrington Sound, Bermuda and its Surrounding Cave Systems(2013-04-23) Stoffer, Jonathan LHarrington Sound, located in east central Bermuda, is almost entirely enclosed by land except for a 26.4 m wide channel called Flatts Inlet. This limited connection to the open ocean restricts Harrington Sound?s tides, resulting in a near 3 hour delay and dampening the tidal range to 35% of those on the coast. By comparing the tidal amplitude and surface area of Harrington Sound, tidal exchange can be determined. Past research has shown Flatts Inlet only supplies the Sound with about half of its tidal water. The remaining tidal exchange enters and leaves the Sound either via groundwater influx through pores in the rock or through the traversable passageways of limestone cave systems in the land that encloses the Sound. The aim of this study was to model hydrodynamic tidal flux and current through marine caves into Harrington Sound. One of the goals of Bermuda?s cave habitat protection plan is to track tidal circulation of water through these cave systems. Information on such cave water transport would facilitate future pollution and nutrient exchange studies. This research was initiated during a six week trip to Bermuda by Jonathan Stoffer as he obtained tidal and water quality data from caves along the perimeter of Harrington Sound. Additional flow data was collected with instruments placed by local cave divers. A YSI 600XLM water quality sonde, Norteck Vector Current Meter, and an in-situ level Aqua TROLL were used to monitor tidal amplitude, periodicity, current velocity, and water quality in cave pools and submerged passages. Profiles of the top 1-2 meters of water at each pool were taken at 56 sites. Tidal gauges were placed in 27 major cave pools surrounding Harrington Sound, as well as Harrington Sound itself, for 48 hours, to monitor tidal propagation through the island. The vector current meter was placed for six weeks to measure water flow in and out of Harrington Sound in six cave passageways known to have high flow rates. The resulting data have been compared to atmospheric data obtained from the Bermuda Weather Service and analyzed using Microsoft Excel, MATLAB and ArcGIS. The final goal of this project was to create a hydrological model able to predict flow rate and water depth in Bermudian caves with water depth data from the ocean and Harrington Sound. In constructing a water budget for Harrington Sound, I was able to account for 72.3% of all tidal inflow and 43.3% of all tidal outflow from the Sound as passing through either Flatt?s Inlet or one of the six tested caves. In creating my tidal models, I was able to achieve an averaged sum of squared deviation (SSD) normalized against count ranging from 5.1x10^-4 to 8.4x10^-4 m^2. The flow model achieved a SSD of 3.8x10^-3 m^2. My data also suggest that exchange between Harrington Sound and other inland waters, through cave systems, does exist.Item A heritage tourism preservation plan for Mogao Grottoes, PR. China(2012-08) Du, Yuanjing, 1981-; Holleran, Michael; Long, Christopher (Christopher Alan), 1957-The Mogao Grottoes, also known as the Mogao Caves or the Thousand Buddhas Caves, is located at the southeast of Dunhuang, northwestern China. It is a very important cultural heritage site on the Silk Road and was designated a World Heritage Site by UNESCO in 1987. Mogao Grottoes is a Buddhist shrine with 45,000 square meters of wall paintings and 3,000 sculptures within 492 cave temples from the 4th to 14th centuries; it is also known as the world’s largest existing cave temple with the richest content of Buddhist art. In 1900, the Library Cave was discovered, in which more than 50,000 well-preserved manuscripts, silk paintings, and other relics of important academic research value were. With its long history and profound culture, Mogao Grottoes became a hot tourist destination in China. A growing numbers of visitors, especially in recent years, bring great challenges for heritage preservation and tourism at Mogao. Dunhuang Academy developed a preservation and utilization project in order to cope with this conflict between preservation and tourism, ensure the heritage is well, and develop sustainable tourism. This paper analyzes the current visitor management methods and the risks from visitors and evaluates the proposals for cave carrying capacity, visitor capacity management, visitor flow management, and a visitor center, including the good points of each and the potential problems associated with the caves preservation, site security, and visitors’ experiences. Finally, the paper discusses the overall project and proposes a recommendation for visitor management and developing sustainable tourism at Mogao Grottoes.Item Microbe-mineral affinity in sulfuric acid karst systems(2011-08) Jones, Aaron Alexander; Bennett, Philip C. (Philip Charles), 1959-; Breecker, Daniel O.; Omelon, Christopher R.Microbial communities influence the kinetics and pathways of reactions involved in the dissolution of a number of minerals (Ehrlich 1996). On a smaller scale these interactions can affect substrate permeability, porosity, and create highly localized biogeochemical conditions. However, a mechanistic understanding of the consequences of microbial surface colonization on calcite dissolution rate has yet to be achieved. More specifically, little is known about the impact of sulfur-oxidizing bacteria activity on the rate of carbonate mineral dissolution, or the nature of the microbe-limestone attachment and interaction. Through a series of laboratory and field experiments the effect of mineral surface colonization by microbial communities, obtained from an active sulfuric acid cave (Lower Kane Cave (LKC), Big Horn Basin, WY), on the dissolution rate of Madison Limestone was quantified. Results from laboratory experiments showed that a microbial biofilm, composed primarily of Epsilonproteobacteria and Gammaproteobacteria growing on a limestone surface oxidized thiosulfate and increased carbonate dissolution rates up to 3.3 times faster than abiotic rates. When all thiosulfate substrate was withheld the community oxidized stored intracellular sulfur, continuing to accelerate limestone dissolution and decreasing pH. This process is sensitive to O2 limitations. Characterization of this aggressive sub-biofilm corrosion was more closely examined by SEM imaging. By comparing mineral surface morphology of colonized chips to non-colonized chips of various carbonate substrates, it was shown that even under conditions near equilibrium with calcite, aggressive dissolution of carbonate substratum occurs exclusively beneath the biofilm. These findings support the hypothesis that (1) sulfur-oxidizing microbial communities aggressively dissolve carbonates in order to buffer the production of excess acidity by neutrophilic communities and (2) biofilm presence affects carbonate mineral dissolution by physically separating a bulk stream water from the sub-biomat environment. Furthermore, it was found that mineralogy affects the degree of establishment of microbial communities in this environment. Results from a series of four laboratory and one in situ reactor experiment showed that limestone and dolostone substratum consistently had higher biomass accumulations than silicate minerals or pure Iceland spar calcite in the same reactor. These results provide evidence to support the hypothesis that mineralogy influences microbial accumulation in sulfuric-acid karst systems. Particularly, neutrophilic sulfur-oxidizing communities accumulate in greater quantities on solid substrates that buffer metabolically-generated acidity. These results also demonstrated the dependence of microorganisms on colonization of a particular mineral surface, possibly in order to gain access to micronutrients bound within solid substrates when exposed to nutrient-limited conditions.Item Physical and geochemical response in cave drip waters to recent drought, central Texas, USA : implications for drought reconstruction using speleothems(2015-08) Hulewicz, Michelle; Banner, Jay L.; Breecker, Dan; Musgrove, MaryLynnA five-year study (2009-2014) of eight drip sites in Inner Space Cavern (IS), a cave on the Edwards Plateau in central Texas, was undertaken to assess the physical and geochemical response of cave drip waters to extreme drought. Drip rate, calcite growth rate, and dripwater geochemistry were monitored before, during, and after the peak of a record-breaking drought in central Texas that began and peaked in 2011, and which continued through to early 2015. Three groups of drip sites are identified based on average drip rate (slow sites, 0.2 -- 0.4 mL/min; intermediate sites, 1.2 -- 4.4 mL/min; fast sites, 6.7 -- 18 mL/min) and similarities in geochemical variation. Drip rates of slow sites have the lowest rate and magnitude of response to changes in hydrological conditions, while fast sites have the largest rate and magnitude of response. In contrast, the geochemical response to drought of the three groups does not correspond to the drip rate response. Slow and fast sites exhibit limited geochemical responses to changes in hydrologic conditions, including dripwater Mg/Ca, Sr/Ca, and Ba/Ca ratios, Sr isotope values, Ca concentrations, and oxygen isotope values. This lack of response indicates limited water-rock interaction (WRI) and/or prior calcite precipitation (PCP) affects these dripwaters. Intermediate drip sites exhibit the greatest geochemical response to changes in hydrologic conditions, including extreme drought, expressed by a decrease in Sr isotope values and an increase in Mg/Ca ratios during drier periods. Quantitative modeling indicates that both WRI and PCP can account for trace-element and Sr isotope variations at intermediate sites. The peak of the drought in 2011 coincides with high cave-air CO₂ and slow calcite growth rates, yet PCP may be an important process at two intermediate drip sites during drought. Geochemistry of intermediate drip waters at IS is likely controlled by water supplied by conduit and matrix flow and may provide the preferred speleothem record for reconstructing past droughts in central Texas using trace-elements ratios. Flow-route characteristics of drip sites at other caves that may be expected to show drought response in terms of trace elements include drip rate response to changes in moisture conditions but relatively low drip rate coefficient of variation and sub-equal matrix- and conduit-flow contributions. The monitoring of key geochemical and physical parameters at a range of sites in a given cave may allow for the identification of speleothems that are most likely to be geochemically responsive to changes in climate, making the speleothem sampling process more informed and less destructive.