This really was the height of folly, as I was alone in the wilderness and had no idea of the potential dangers. I currently work in the field of ground control engineering, and have firsthand knowledge of numerous fatalities that occurred in active mines when rock fell out of the roof without warning. I have also become more familiar with the extensive engineering design work, and variety of support systems, required to develop and maintain a mine opening. The "old timers" were often lucky by developing small openings in hard rock, but modern mining engineering indicates that time does not favor stability.

A more insidious danger is represented by a lack of breathable air. In sealed underground openings, the air may have become "stale" by not being circulated through the outside. In modern mines, a staff is devoted to designing and maintaining ventilation systems that cycle fresh air through the mine. Some gases displace oxygen, but are colorless and odorless and give no warning of danger until the person suddenly realizes that they feel as though they have been holding their breath for several minutes. This is a condition known to miners as "black damp" that can cause loss of consciousness or death.

While working in Bolivia, I entered over a dozen small mines in a district that had been developed initially by the Spanish, or perhaps even the Inca, and later by a Polish mining engineer in the early 1900’s. The most modern operation had closed in the 1980’s, when the underground portion of the mine was abandoned as uneconomical, but a small open pit was developed that intersected some of the old workings. As a geologist working to unravel the geological history of this area, I entered the mine to document the relationships between intrusive phases. As I was intently concentrating on the last face of the mine, trying to decide if the rock was rhyodacite or dacite, I suddenly noticed a warm, tingly, numb sensation in my nose and lips. Panicked, I exhaled what little air remained in my lungs and held my breath, while at the same time wheeling and sprinting back up the tunnel. Weird, ghastly shapes of rotten canvas and timbers danced in the shadows thrown by my flashlight. I had little hope of sprinting the nearly 300 yards to the mine mouth, but as gray spots floated before my eyes, I determined to keep my legs pumping to at least get out of what might only be a pocket of bad air. Then I saw a sliver of light where the floor of the open pit had intersected the tunnel. Fresh air! I ran to the cut and gulped in the thin mountain air. Although the air smelled like decaying sulfides, at least the threat of black damp was gone, and so my panic subsided enough to allow me to walk briskly out of the mine.