Album caption: Wyo - Y.S.N.P.
Index card: Green Dragon Spring, discharging acid Cl-SO4 water of long-debated origin. Only visible production of S and sulfates (yellow and orange) is on roof and sides of Dragon's Mouth. Water discharges from three vents (one under ledge) into Gray Lakes, and both features have nearly the same total discharge. Green Dragon is now viewed as partly recirculated Gray Lakes' water in which thermophylic organisms oxidize H2S to sulfate at high temperatures. Surging in foreground is about .4 m in diameter. Norris Geyser Basin. Yellowstone National Park. Wyoming. September 1947.
Published as Figure 24 in U.S. Geological Survey. Professional Paper 1456. 1988.