Members attending the 2010 Annual Meeting of the Association of Outdoor Lighting Professionals got the opportunity to experience the latest featured attraction at Natural Bridge Caverns, the “Illuminations Tour” of the Jeremy Room. The lighting system for the cave was developed with the assistance of one of their local association members, Jim Boyd of Boyd Lighting Designs. Because of the highly corrosive environment and almost 100% humidity present, Boyd Lighting Designs was brought in to design and specify a lighting system which would hold up under these extreme conditions and provide pristine white light to show the beautiful features of the cave in the most natural and complementary way possible.
Exploring the Hidden Passages to a depth of 180 feet, the Illuminations Tour is accessed by 185 steps. As small groups are led by one of Natural Bridge’s guides, the guide synchronizes his presentation with a custom-designed lighting system that strategically reveals glistening cave formations one at a time, beautifully unfolding long-held secrets of the cave. Many of the formations actually sparkle from the light reflecting off calcite crystals that adorn them. First-time cavern visitors may be surprised by the colors of some formations, sometimes subtle, sometimes deeper, depending upon the mineral content.
“Because the Illuminations Tour features interplay between light and dark, we’re able to appreciate the cavern environment and formations more fully, and with a depth of field we wouldn’t experience otherwise,” said Brad Wuest, president and chief executive officer of Natural Bridge Caverns. “We believe we are giving guests an experience they haven’t seen anywhere else in Texas.” The tour features two vast underground chambers and highlights such extremely delicate and well-formed formations as unusually long ‘soda straws,’ waves of ‘cave ribbon’ and a profusion of intriguing ‘welt and turnip shields.’ The formations are plentiful and beautiful, even breath-taking, and nearly all of them are still growing.
“Natural Bridge Caverns is called a living cave because the cave formations are still being formed by water dissolving rock,” explains Brian Vauter, Cave Geologist for Natural Bridge Caverns. In actuality a complex process of variables, a simple explanation of cave formation is that as rainwater falls from the sky and seeps through the soil, it picks up carbon dioxide and makes carbonic acid. This slightly acidic water then seeps through the ground absorbing minerals like calcium carbonate along the way. Inside the cave, the mixture drips from the ceiling and the minerals in the water are left behind. Over hundreds of thousands of years they create the cave’s formations, including icicle-like stalactites on the ceiling and pillar-like stalagmites on the floor. The rate of growth varies, but generally, it’s about one inch every 100 years.
Natural Bridge Caverns was discovered in 1960 by four cavers from St. Mary’s University in San Antonio. For years it appeared that the entrance sinkhole was the beginning of Natural Bridge Caverns and that the only passages extended for two miles to the north. Later, the owners and the cavern developers began to wonder, “what if the sinkhole formed in the middle of the cave and not at the beginning?” If true, this would mean the possible existence of additional passages to the south. With lack of any obvious entrances on the surface, the only way to test such a theory was to drill exploratory well shafts into the ground. In 1968, while drilling south of the main cavern entrance, an additional half-mile of cavern was discovered and was named the Hidden Passages. Although parts of the Hidden Passages were open to tours in 2002, the Illuminations Tour includes a chamber not open to tour groups until now.
The Illuminations Tour lasts approximately 70 minutes. One special feature of the tour occurs when all the lights are turned off and guests experience total darkness. Comfortable, rubber-soled walking shoes are recommended in the caverns. The temperature is 70 degrees with high humidity.
A family-oriented attraction, Natural Bridge Caverns offers a variety of activities for all ages. The Discovery Tour explores the originally discovered, and very dramatic, North Passages. The more adventurous might want to try the Watchtower Challenge, season and weather permitting, and test their climbing skills on one of the largest outdoor climbing towers in Texas. The Mining Co. is a kid-friendly mining sluice where little ones can pan for gems, minerals and fossils.
Natural Bridge Caverns is open daily from 9 a.m. to 4 p.m., with extended hours for spring and summer. The caverns are located 30 miles north of downtown San Antonio and eight miles west of IH-35 at exit 175/Natural Bridge Caverns Road. For additional information, visit www.naturalbridgecaverns.com or phone 210-651-6101.