Field Trip to Natural Bridge Caverns with UH Geology and Non-Geology Students

Trip Sponsored by the Department of Earth and Atmospheric Sciences

Drip Water Sample
Hands-on experience inside the cave. A student collects a drip water sample while another student metered the time to calculate the drip rate. Photo credit: Ali Raza

In October, eighteen University of Houston students (eight undergraduate and ten graduate), two guests, and the course instructor experienced a one-day field trip visit to Natural Bridge Caverns in San Antonio. The trip was part of the hands-on class activities for GEOL 3344 Paleoclimatology and GEOL 6338 Paleoclimate.

This is a new course developed by Ny Riavo Voarintsoa, assistant professor in sedimentary geology, in the Department of Earth and Atmospheric Sciences at the UH College of Natural Sciences and Mathematics. Dr. Voarintsoa is currently focusing on paleoclimate reconstruction using various sediments, including cave sediments.

Cave Decorations
Students view the beautiful cave decorations inside Natural Bridge Caverns. Note the massive speleothem varieties (columns, stalagmites, stalactites, and flowstones) and the neat and clear cave pool. Photo credit: Michael Lukas

The field trip was planned around the weekly lecture scheduled on speleothems for an integrated picture linking climate and cave sediments. Speleothems are secondary formations in caves.

Prior to going on the field trip, students learned a simple, instrumental calibration in class. They were shown how to calibrate pH, which is a measure of the cave water acidity, for a water mix containing dissolved inorganic carbon. This approach gave them some ideas about mineral precipitation or dissolution in caves.

While at the Natural Bridge Caverns, students learned various atmospheric characteristics that may influence the formation of speleothems. These included measurements of carbon dioxide outside and inside the cave. Carbon dioxide, a key component of the atmosphere, plays an important role in the formation and dissolution of carbonates.

Students & Dr. Voarintsoa
Students, one of the guests, and Dr. Voarintsoa inside Natural Bridge Caverns. The background is a limestone decorated by soda straws. Photo credit: Voarintsoa

Inside the cave, students learned the various forms and shapes of speleothems, including the most common, stalactites (rocks growing from the ceiling) and stalagmites (rocks growing from the floor of the cave), and other eye-catching forms, such as columns, soda straws, cave foli, draperies, flowstones, and cave pools.

Stalagmites are important recorders of climate and environmental changes, and they are fed by cave drip waters.

Students also learned how to measure drip rates in caves as a simple approach to appreciate the amount of water supply. They measured the drip water temperature because it is well known that carbonates can reliably archive past temperatures using special elements preserved in them.

These activities offered a simple, but valuable, hands-on experience, and the discussion during the field trip was also invaluable in deepening the students’ understanding of cave systems and their potential to preserve climate and environmental changes.

Acknowledgments

Thanks to the teams at Natural Bridge Caverns, including the admission team lead and the tour guides, and specifically our tour guide, Nathan, for letting us visit the cave and learn about cave formations and gain some hands-on practice on few practical measurements done inside a cave. We also thank the Department of Earth and Atmospheric Sciences for funding this trip.