Every February for a short time in Yosemite National Park, sunshine strikes Horsetail Falls and creates a visual effect that resembles a waterfall on fire. Similar kinds of phenomena happen in the Grand Canyon of the Yellowstone depending upon the seasonal arc of the sun, weather and steam pouring out of the ground. "What marvelous hot springs lies hidden in this canyon cliff cleft revealed on this cool morning by an ephemeral tease of steam," Fuller writes of this image. " Photo by Steven Fuller