GUIDE TO THE NORRIS GEYSER BASIN 15¢ [Illustration: uncaptioned] NORRIS GEYSER BASIN The Norris Geyser Basin was named for Philetus W. Norris who served as Yellowstone’s second superintendent from 1877 until 1882. Although he did not discover it, his explorations and reports were largely responsible for calling attention to that area. Norris is considered to be the hottest and most active geyser basin in Yellowstone. Here geysers and hot springs exhibit greater change in activity over a short span of time than elsewhere in the park. It is not unusual for a new hot spring to come into existence literally overnight. The new feature may last for just a few days or perhaps a month or so; upon occasion some have endured for many years. Because of constant change in the thermal features, the ground here is unstable and hazardous in many locations. Therefore, you are required to stay on designated trails and boardwalks at all times. This not only protects you from possible serious burns but also helps preserve the features as well. Remember also not to throw any objects into thermal features. Debris of any kind in a hot spring or geyser could clog the vent and destroy the feature. Because many scalding hot pools and run-off channels are near trails and boardwalks, pets are not permitted on the trails. The fact that thermal features change may come as a surprise, but remember that geysers, hot springs and other thermal phenomena are subject to natural stresses just like plant and animal communities. Of course the changes in thermal activity result from a different set of factors than those affecting plants and animals. Can you guess what they might be? Shifts in the earth’s crust (earthquakes) result in movements along cracks and fissures in the ground. These tremors usually cause changes in the underground “plumbing systems” of thermal features, thus altering activity patterns. Look for signs of recent activity variations as you walk along the trails, or ask a naturalist if there have been some recent changes. As you explore, look closely at the often intricate formations around the edges of a few hot pools, geysers and in some thermal runoff channels. You will notice a mineral called sinter or geyserite (a form of silicon dioxide, SiO₂) being deposited like tiny spines. These rather prickly formations result when geyserite is deposited from slightly acid water, a characteristic of most thermal water in the Norris area. This is in contrast to the bead-like structures that result when geyserite forms from slightly alkaline water found in thermal features in the Old Faithful area.