Home | Research | Publications | Teaching | People | Facilities
Open Graduate Student Position
Sulfuric acid has created some of the largest caves on the planet. Many of these, such as the Lechuguilla/Carlsbad cave complex in New Mexico, are "dead" in the sense that sulfuric acid production and limestone corrosion are no longer occurring. Actively-forming sulfidic caves host rich microbial ecosystems that enhance the rate of cave formation by producing sulfuric acid as a waste product. These caves are human-accessible windows into a largely inaccessible, below-ground world. They offer the opportunity to study geological and biological processes that affect large areas of the earth's subsurface, including those that create porosity in carbonate rocks (oil reservoirs) and cause diagenetic effects in carbonate sediments (climate and other records of earth history).
Last but not least, sulfidic caves are extraordinary model systems for ecology and evolution. Like hydrothermal vents and hot springs, they are geochemical "islands" that allow for tests of gene flow between isolated microbial populations. Genetic information encoded in the genomes of extreme acidophiles colonizing sulfuric acid drips on the cave walls offer clues about survival at one of the outer limits of life (pH 0-1). Chemoautotrophic animal-microbe symbioses that we recently discovered in sulfidic caves are similar to those at marine vents and seeps but younger (less evolved), providing a tantalizing glimpse at the ecological and genetic forces at work in the creation of biological partnerships across the domains of life. These any many other aspects of the biology and geology of sulfidic caves remain to be fully explored.
Sulfidic Caves in Italy
The Frasassi cave system is a large, actively-forming sulfidic cave located in central Italy. The lowest levels of the cave complex host an isolated ecosystem powered by sulfur-cycling microorganisms. We have initiated genetic, microbiological, geochemical and isotopic studies of both acidophilic and neutrophilic microbial communities at Frasassi in collaboration with Italian colleagues. Frasassi also hosts stratified lakes with sulfidic bottom waters, providing a modern analog for microbial biogeochemistry in stratified oceans in earth's past. Numerous other sulfidic caves are accessible in the Italian Apennines, providing an opportunity to study the time scale for microbial evolution among physically and geochemically isolated microbial populations.
A recent expedition to Grotta Nuova di Rio Garrafo, a hot sulfidic cave near Acquasanta Terme, revealed "snot bubbles" and pH 0-1 microbial "curtains" as well as snottites on cave walls.
A gallery of Italy cave fieldwork photos can be viewed here. Images are the property of the Macalady Geomicrobiology Group (PSU) and the Coldigioco Cave Science Consortium. Photo credits vary, please contact me for more information about specific images. Caves shown include many parts of the sulfidic cave systems developed in the Frasassi and Rio Garrafo gorges.
Sulfidic karst in Mexico
See Caves of Tabasco Project
Images of Frasassi cave biota:
Coldigioco Geological Observatory
The Frasassi Gorge
Cave scientist and collaborator Sandro Galdenzi cleans his equipment.
The Frasassi caves were discovered in 1971 by a group of Italian cavers in the Gruppo Speleologico Marchigiano CAI. Caver Alessandro Montanari (shown above) is now Director of the Osservatorio Geologico di Coldigioco, a world class independent research facility for earth science research and education. Some parts of the Frasassi complex can be visited by the public, and are among the largest show caves in Europe.
Smaller is Better Principle in Action
Website designed by Lev Horodyskyj. Maintained by Jenn Macalady