Photos from our visit to Flagstaff which included a "Lava River Cave" hike and visit to the USGS headquarters Oct 23, 2004. The Lava River Cave (or Government Cave) is a 675,000 yr old lava tube formed when the Hart Prairie shield volcano erupted. Temperatures in the tube (a bit cooler than 675,000 years ago) were approx 35F - 45F, but never uncomfortable. The first significant snowfall of the year left ample ammunition for an impromptu snowball fight at the entrance following the hike.