Castle Geyser, located in the Upper Geyser Basin, erupts every 10-12 hours. The water phase lasts about 20 minutes and can reach heights of up to 100 ft. This is followed by a thunderous steam phase that can sometimes continue for an hour. Castle is a sinter cone and was named by members of the Washburn/Doane Expedition in September 1870 in Yellowstone National Park. Image taken by Ann C. Skelton of Nature In Pixels.

Overall size is 6¼”x4½” folded. White envelopes are included. Inside of notecards are blank so you can inscribe your own heartfelt message.