National Science Foundation
photo of caverns


In 2006, Kartchner Caverns was added to the National Science Foundation`s worldwide network of Microbial Observatories. The goal of the Microbial Observatories program is to study and describe the phylogenetic (who is there) and functional (what do they do) diversity of microbial communities on the beautiful formations found in the cave.  Kartchner Caverns is the only cave in the network.  The Kartchner Caverns Microbial Observatory is a collaboration between the laboratories of four investigators at the University of Arizona: Dr. Raina Maier, Dr. Leland S. Pierson III, Dr. Barry M. Prior, and Dr. Rod Wing.

Kartchner Caverns was discovered in 1974 by two University of Arizona students whose hobby was caving or spelunking.  The cave is located in the Whetstone Mountains near Benson, AZ and is considered a “living cave” because it has been preserved so that water still actively drips and the cave formations continue to slowly grow. In the short time since its discovery, Kartchner Caverns has been widely acknowledged as a truly unique and beautiful example of carbonate cave development.  

Map with location of Kartchner Caverns in Benson Arizona, USA

The carbonate formations in Kartchner are known as speleothems.  Carbon dating suggests that the formation of the speleothems in Kartchner began >190,000 years ago.  These formations have continued to grow to the present day due to percolating waters that enter the cave from the soil surface. To view several 360 degree interactive images for different parts of Kartchner Cavern, please click here.

Beginning in 1988, selected parts of Kartchner have been slowly and carefully developed to ensure that it remains a living cave while serving as a hugely popular State Park attraction.

Airlock environmental doors at the cave entrance A tunnel that was created to gain access to the cavern

Double airlock environmental doors at the entrance to the cave tunnel and again at the entrance to the cave rooms help to minimize the loss of humidity from the cave. This is important to maintain the dripping water that allows the formations to continue to grow.

An example of a tunnel that was carefully blasted through the hillside to gain access to the rooms of Kartchner for tourism.

In order to prepare for the public opening of the cave in an environmentally sensitive manner, Arizona State Parks had the foresight to contract multi-year, multi-disciplinary scientific studies of the Caverns. The importance of these scientific endeavors should not be underestimated: Kartchner Caverns is one of the most thoroughly studied caves in the world with one of the best cave microclimate monitoring programs. For the last 15 years, 13 environmental stations have monitored on an hourly to monthly basis for temperature, humidity, pan evaporation, carbon dioxide and radon levels.

Cave air temperature varies throughout the cave from 64 degrees to 71.7 degrees F (mean 67.6 degrees F.

The mean humidity throughout cave is 99.4% and the average evaporation rate is 9.4 mL/m2/day.

The natural cave entrance in the Big Room generally inhales between October and May, and exhales between June and September. Radon and carbon dioxide levels vary seasonally (highest in summer) averaging 90 pCi/L and between 600 ppm and 6200 ppm (carbon dioxide in the atmosphere is 380 ppm), respectively. Airflow beyond the Big Room is very restricted as there are no other natural openings. Consequently, atmospheric conditions are much more stable in these areas.

The mineralogy of Kartchnerstalactite

Unlike most limestone (carbonate) caves, Kartchner is adjacent to igneous and metamorphic terrains.  Alaskite granite borders the Escabrosa Limestone along fault zones to the west and Pinal Schist underlies the entire cave. These fault zones, within an active tectonic region with a high geothermal gradient, have acted as avenues for ascending hydrothermal solutions and for the formation of minerals such as quartz, illite, and rectorite. There are numerous gypsum, hydroxylapatite, and hematite formations, and rare aragonite speleothems. But most dramatically, the caverns have abundant and diverse calcite speleothems including actively-growing stalactites, soda straws, stalagmites (including totems and fried eggs), columns, draperies, shields (including parachute, welt, and turnip), flowstone, popcorn, helectites, and boxwork. Mineral discoveries in Kartchner include the first identification of birdsnest quartz, rectorite and nontronite from a cave, the first modern description of nitrocalcite, extensive brushite moonmilk flowstone, and a 21'2" soda straw in the Throne Room - the world’s second longest. This varied assortment of exquisite formations has positioned Kartchner Caverns as one of the top ten caves in the world in terms of mineralogical diversity

General Cave Formation Timeline

Years Ago
Cave Event
~350,000,000 - 300,000,000 Deposition of Escabrosa Limestone
~15,000,000 - 5,000,000 Basin and Range faulting
~500,000 – 200,000 Dissolution of cave at water-table
~194,000  Oldest identified speleothem in cave
~120,000 - 70,000 Major period of speleothem growth
~80,000 years ago  Sloth enters or washes into cave
50,000 - 40,000 Myotis (bat) use of Rotunda and Throne Room
70,000 - 10,000 Speleothem growth declines
10,000 years ago – Present Increasing aridity, continued decreasing speleothem growth

Map of Kartchner Caverns

updated 7/2009

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