January 2, 2013

LASI V: Dr. Volcano in the Cave of Crystals, Naica, Mexico

Posted by Evelyn Mervine

Note: Dr. Dougal Jerram—aka “Dr. Volcano”— presented a talk, “When Shallow Intrusions Make Silver Mines—A Journey into Superman’s Cave, Naica, Mexico” at the LASI V workshop in Port Elizabeth, South Africa in October 2012. The article below is based on this talk and also an interview with Dr. Volcano. Over the next few weeks, I will be highlighting some of the research that was presented at the LASI V workshop. This is the first post in that series.

Dr. Volcano in Ethiopia during shooting for the BBC (http://www.dougalearth.com/media.php).

The title of this blog post, “Dr. Volcano in the Cave of Crystals”, may sound like the title of a comic book or a science fiction story, but I can assure you that both Dr. Volcano and the Cave of Crystals are very much real. I had the pleasure of meeting Dr. Volcano and hearing about his visit to the Cave of Crystals at the LASI V workshop back in October 2012.

Dr. Volcano is also known as Dr. Dougal Jerram, who in June 2011 left his academic position at Durham University to set up DougalEARTH Ltd. and embark on an exciting new career as an independent geological consultant, researcher, and also a media consultant, becoming involved in science outreach and popular science entertainment. On his website DougalEARTH, Dr. Jerram states that he is, “aiming to make science more accessible to the general public and promoting our understanding of the planet.” In his science outreach and media work, Dr. Jerram is known as “Dr. Volcano.” The title is certainly appropriate since he has published dozens of scientific research articles about volcanoes and has also penned two books about volcanoes, The Field Description of Igneous Rocks (with Nick Petford, 2011) and Introducing Volcanology: A Guide to Hot Rocks (also 2011). For his scientific outreach and media work, Dr. Volcano has appeared on television programs for stations such as the BBC, The History Channel, and National Geographic.

The Channel 9 News Team in the Cave of Crystals. Picture courtesy of Andy Taylor.

As part of his media work, Dr. Volcano had the extraordinary opportunity to visit a place in Naica, Mexico known as Cueva de los Cristales or the Cave of Crystals (http://en.wikipedia.org/wiki/Cave_of_the_Crystals) in the Fall of 2011. Dr. Volcano visited the cave as part of a news team for a 60 Minutes documentary for Channel 9 News, Australia. The cave is also known as the Giant Crystal Cave and Superman’s Cave, since it resembles the Arctic home of the comic book character Superman. Located about 1000 feet (about 300 meters) below the Earth’s surface, the cave contains gigantic crystals of selenite (gypsum, CaSO4•2H2O) that are some of the largest known crystals on Earth. The largest crystals in the cave are nearly 40 feet (12 meters) tall!

The Cave of Crystals was first discovered in 2000 by miners who were excavating a new tunnel for the silver, zinc, and lead mine owned by the Industrias Peñoles mining company. Previously, a similar cave known as Cueva de las Espadas or the Cave of Swords was discovered in 1910. This cave is also located at Naica but at a shallower depth of about 400 feet (about 120 meters). However, the selenite crystals in the Cave of Swords are smaller, with a maximum size of about 6 feet (2 meters). In addition, many of the crystals from the Cave of Swords have been removed from the cave and transported to other places, such as museums.

A map of the Naica mine showing the locations of the Cave of Swords and the Cave of Crystals. Figure taken from Garcia-Ruiz et al. (2007).

Dr. Volcano explains, “We had the very lucky opportunity to go into the Naica caves in Mexico. These caves are very special because they have—arguably—the largest crystals on the planet. These crystals are gypsum, which is calcium sulphate (dihydrate). We were able to get into these caves after two years of negotiation with the Mexican mine and the government there.”

Prior to mining, the Cave of Crystals was underwater. The cave is only exposed because the mining company has pumped water away, lowering the groundwater level so that mining can proceed deeper. Naturally, the groundwater level is about -110 meters. Once pumping stops, the Cave of Crystals will again fill with groundwater. And not just any groundwater. The cave will fill with very hot groundwater since the Earth is quite warm at 300 meters depth. Research (e.g. Ruiz-Garcia et al., 2007) suggests that the enormous selenite crystals found in the Cave of Crystals likely formed in low-salinity fluids that were at a temperature of approximately 54 degrees Celsius. The selenite crystals grew very slowly over hundreds of thousands of years, enabling the crystals to reach their enormous sizes.

While no longer filled with hot fluid, the Cave of Crystals nevertheless remains an inhospitable environment for humans. Temperatures in the cave are 45 to 50 degrees Celsius, and the humidity ranges from 90 to 100%. While the mining shafts are cooled for the workers, the Cave of Crystals is not cooled, which helps preserve the giant selenite crystals. Visiting the Cave of Crystals is therefore no easy feat.

Dr. Volcano describes, “You go inside the cave, and you’re in temperatures of around 50 degrees Celsius, and the humidity is around 100%. One of the biggest problems when you go into an environment like that is that your body is unable to cope with that environment, and you effectively start dying the minute you enter the cave.”

In such an extreme environment, humans can only survive unaided for a few minutes.

Dr. Volcano elaborates, “The biggest problem you have is that when your body temperature is the lowest temperature in the cave, everything that your body does to try to cool itself doesn’t work. It tries to sweat, but the sweat doesn’t evaporate because there’s 100% humidity, so there’s no cooling from evaporation. You breathe in air, but the air is hotter than your internal body, so it starts heating up your body. You start to pant, like a dog, which is a natural reaction to try to cool yourself, but as a result you end up heating the interior of your body more quickly. We found that after 9 minutes in the cave without any sort of protection, our body temperatures rose to 39.5 degrees Celsius, which is quite dangerous. We had an Australian medic with us (David Rosengren), and he said that if your body temperature goes over 40 degrees Celsius, you could very rapidly deteriorate and even die.”

Fortunately, the Channel 9 news team came prepared.

Dr. Volcano explains, “We had a kind of solution, which we called ‘Formula 1 Geology.’ We used the same sort of suit that people in extreme sports, such as Formula 1 racing, use in environments where they can get very hot very quickly. It’s a close-to-the-body suit with piping inside that pumps cold water around the body. You wear a backpack with ice water, and an electric pump moves that cold water around the suit. With the suit, we could safely stay in the cave for about 25-30 minutes. Ultimately, if other people could refill the backpacks with more ice cold water, people could possibly stay in the cave much longer.”

As difficult as it is for humans to explore the Cave of Crystals at present, if mining ever stops at the Naica mine then it may become impossible to visit the cave since it will again fill with hot fluid.

Dr. Volcano wonders, “The giant crystal caves are only exposed because man is pumping the groundwater out. The biggest dilemma that we have for this natural wonder of the earth is: if the mining stops, then in principle the water level will rise again, and the Naica caves will be underwater again. I pose to the general public: what should be done—if anything—to save the Naica caves?”

I wonder that, too. It may be that the unique and remarkable Cave of Crystals will only be accessible for a brief time, only as long as the Naica mine remains in business.

Links and References:


The 60 Minutes Channel 9 News Documentary on the Cave of Crystals

Naica Project

Garcia-Ruiz, J.M., Villasuso, R., Ayora, C., Canals, A., and Otalora, F. 2007. Formation of natural gypsum megacrystals in Naica, Mexico. Geology, Vol. 35, No. 4: 327-330.