It was hard to knock back the opportunity to join 60 Minutes Australia for a trip into The Crystal Cave in northern Mexico. After 2 years of (no doubt costly) negotiation, producer Danny Keens was given permission to take a crew into the the tightly guarded cave located a mile beneath the surface within the Penola lead mine in the desert mountains of Naica in northern Mexico.
Discovered in 2000 by two brothers doing mine blasting, the cave has formed along a volcanic fault line where, filled with volcanic heated water in a closed environment for centuries, gypsom minerals have consolidated to produce massive selenite crystaline structures at a scale up to 10 times greater than previously discovered.
Along with TV journalist Michael Usher and crew (cameraman Andy Taylor and soundman Chick Davies), I was invited along to provide medical support. We were joined by world renown UK volcanologist Dougal Jerram to complete the team.
Why was medical support needed? The environment necessary to produce such an awesome display of nature is such that human life cannot survive for any prolonged period. With a minimum temperature of 45 deg C and an average humidity of 100%, the bodies ability to lose heat is immediately overcome.
Any ability to lose heat through evaporation, conduction, convection and radiation are overwhelmed.
From the moment you step into the cave you begin to cook as the body temperature attempts to equilibrate with the environment.
My research prior to arriving (and there was very little to help) suggested that at best we could safely stay inside the cafe for 10 minutes at the most. This proved to be completely correct. There are no words to describe the overwhelming assault on the body senses as you step into the cave. It is easier to describe the sense of overwhelming panic to get out that begins to develop after about 10 minutes inside.
So what strategies did I employ to keep us safe?
- 2 pedestal fans purchased from a hardware store in Chihuahua and plugged into a power source in the mine ramp outside the cave entrance
- A handful of cheap plastic pump spray bottles
- 2 eskies with chilled bottled water – restocked with ice by mine security staff
- strict time keeping to ensure that exit from the cave was enforced after 10 minutes
- Approx 1 hour rest time in the cooler (35 deg C) and less humid (75% humidity) environment of the mine tunnel adjacent to the cave
Spraying cool water over our face and neck using simple pump spray bottles and sitting in front of a cheap pedestal fan to support evaporative cooling was a very efficient method of cooling.
It was hard to achieve much with such a short time frame so we trialled some cooling suits to see if we could prolong trips inside the cave. With a small backpack full of ice and water and a small battery operated pump to circulate the iced water through tubing sewn into the shirt and pants, we were able to stretch our time inside the cave out to 20 minutes.
The crystals are extraordinary. The raw size and beauty of the cave assaults the senses in much the same way as the oppressive conditions. It is not until we had been into the cave multiple times that we were able to control our senses and emotions to really appreciate the extraordinary opportunity we had been given.
There are very few places on the planet that are not accessible to the general population and this is one of those such places. I am extraordinarily grateful to have been given the opportunity. To get everyone out safe and sound was an added bonus.
Go to the 60 Minutes Video page and search The Crystal Cave to see the story.
If you like that story then also search Tracking a Killer, the story of our research into deaths due to hyponatraemia on the Kokoda Track.
Awesome stuff!
Theoretical question: Could a breathing apparatus be derived that would cool and dehumidify the inspiratory gases, possibly based on the current technology in mine rescue rebreathers? I’m sure that the closed circuit rebreathing systems would probably work, although they do not cool the inspiratory gases.
The reason I ask is that I wonder if a substantial degree of the hyperthermia in the crew exploring the cave is due to the respiratory influences of the
atmosphere you describe? --even more so than the effect of the atmosphere on the surface of your skin?
Good comment Jimmy D. There is no question that chilled inspired air would extend the time inside the cave by reducing exposure of the huge alveolar surface area to the heat.
In 2007 a team of italian scientists spent 6 months with access to the cave culminating in a Nat Geo documentary. They explored all sorts of cooling options to try and extend their time in the cave and certainly used cooled air breathing apperatus as one of the options.
The biggest challenge was finding cooling mechanisms that
-- was not so heavy it was impossible to wear
-- had a mechanism to power itself in the austere environment
-- maintained sufficient cooling power itself when exposed to the environment
One of the limitations we had with our suits was that even though the ice bricks we used were in an insulated backpack, it melted so quickly (within 5 minutes) that after a short period of time we were pumping warm water around the suits and lost the benefit. I used to try and extend the life of my ice by switching the pump on and off intermittently and this seemed to help a little bit.
The italian team used apperatus where the inhaled air passed though ice bricks in a back pack BUT the ice melts so quickly inside the cave (despite insulation) that the benefit of this was limited. Check out the link to this site which explains their experience -- http://www.naica.com.mx/english/internas/interna5_1.htm.
I am not sure I can answer your question whether respiratory exposure is a greater contributor to heating than skin exposure but I can say that both definitely contribute. Breathing in the hot humid air was certainly a challenge!