We left Waitomo bright and early on the 7th morning, eager to reach Lake Taupo before noon. Lake Taupo is a spectacular, massive lake, much bigger than Lake Rotorua, which we’d seen earlier in the trip. It’s the largest lake in New Zealand, known formally as “Great Lake Taupo,” and as we learned that day, it was formerly a supervolcano. Several thousand years ago, a supervolcano erupted, leaving a large, cauldron-like depression in the ground called a caldera. Lake Taupo formed in that caldera. Because of the volcanic activity surrounding the lake, there are several hydrothermal vents at the bottom of the lake (360ft below) that make the temperature of…