Angel Falls
Angel Falls is a spectacular cascade of white flowstone and drapery that fluoresces under a black light. The formation is situated above the Ghost Room, along the wall just beyond the metal platform.
Geology
Cave Formations
Calcite purity increases with depth, since sediment and other impurities are gradually filtered out as water must percolate further to the cave rooms. This is why the Angel Falls formation is so white. Along with increasing purity comes increasing translucence, which is part of the reason why these formations glow under a black light. The “see-throughness” of the calcite allows the UV rays to interact with fulvic acids trapped in the crystals (van Beyner et al).
Soils produce a variety of organic compounds from decaying matter. This includes fulvic acid groups, humic acid groups, and groups of other large molecules. These organic acids are common in forest soils, and can be dissolved in water and brought down into the cave. Both acids are likely present at Angel Falls, but fulvic acid is the primary compound responsible for fluorescence (Roth 41; van Beyner et al; Shopov 41).
Opposite from Angel Falls, pendants and vermiculations can be seen. The pendants hang down from the ceiling and are parts of the marble that were not eroded away. Their jagged shapes indicate that nearby marble either dissolved away by a rapidly receeding flood or broke off (Lundberg 318).
Vermiculations and sediment deposits cling to these ceiling-hanging pendants. The vermiculations indicate where sediment slowly dried out, allowing the clay particles to attract to one another (Bini, Gori, and Gori).
Bini, Alfredo, Cavalli Gori and Silvio Gori. “A Critical Review of Hypotheses on the Origin of Vermiculations”. International Journal of Speleology, v.10: 1, 1978.
Lundberg, Joyce. “Karren.” Encyclopedia of Caves. David Culver and William White, ed. Burlington: Elsevier Academic Press, 2005. 315-321.
Shopov, Yavor. “Speleothems: Luminescence.” Encyclopedia of Caves and Karst Science. John Gunn, ed. New York: Fitzroy Dearborn, 2004. 695-696.
Roth, John. “Interpretive Manual for the Monument’s Showcave”. Cave Junction: Oregon Caves National Monument, 2011. 41.
van Beynen, P., R. Bourbonniere, Derek Ford., and H. Schwarcz. “Causes of Colour and Fluorescence in Speleothems.” Chemical Geology. 175 (2001) 319-341. Print.
White, W. B. “Paleoclimate records from speleothems in limestone caves.” In Studies of Cave Sediments – Physical and Chemical Records of Paleocllimate. Kluwer Academic: New York, 2007. 135-75.