Hello, I’m Park Ranger Orville Bach, and welcome to one of the most unique and dynamic places on planet earth, the Upper Geyser Basin of Yellowstone National Park. Here is the largest concentration of geysers in the world. Over half of Yellowstone’s 300 active geysers are located here, including Castle Geyser, so named for the 12 foot tall mineral formation.
Geysers are extremely rare in the world, because in order to exist, four necessary ingredients must be present. First, heat. Here in the Upper Geyser Basin, we are standing in the middle of one of the world’s largest living, breathing supervolcanos, measuring 30 by 45 miles across. Scientists believe that molten rock, or magma, lies only about five to eight miles beneath the surface. The second ingredient is water, and here, about 18 to 20 inches of precipitation falls, mostly in the form of snow. There is a very large aquifer underneath us, where the water becomes superheated to temperatures well above boiling.
The third ingredient is a series of cracks and fissures, or a plumbing system, which allows the water to filter down one to two miles, coming in contact with extremely hot rocks. These cracks may contain narrow constrictions, where pressures build up. The fourth and final ingredient consists of the necessary minerals that coat the plumbing system, allowing tremendous pressures to accumulate. Here, the mineral is called siliceous sinter, silicon dioxide, or simply geyserite. It is a very common mineral in rhyolytic, volcanic rock, and it builds very slowly at the surface, forming about one inch per 50 to 100 years. It is almost like taking cement or concrete and reinforcing a pipe.
Geysers are not only very rare and unique, but they constantly change. Join me as we walk around the corner and let’s take a closer look at Castle Geyser.