Midway Geyser Basin contains a small collection of mammoth-sized springs. Midway is part of the Lower Geyser Basin, but because of its isolated location between the main features of Lower and Upper geyser basins it became known as Midway. Rudyard Kipling, who visited Yellowstone in 1889, immortalized this basin by referring to it as “Hell’s Half Acre.” Even today it is still remembered by that name. Despite its small size Midway possesses two of the largest hot springs in the world. Grand Prismatic Spring, nearly 370 feet in diameter, sits upon a large mound surrounded by small step-like terraces.
The other feature, Excelsior Geyser, erupted nearly 300 feet high before the 1900s. It is now a dormant geyser and is considered a hot spring, discharging more than 4050 gallons of boiling water per minute. Other colorful springs include Turquoise and Indigo springs, known for their pale and dark blue colors. Across the Firehole River from Excelsior and Grand Prismatic springs are a series of small isolated, pristine springs and mud pots. The Rabbit Creek drainage possesses some colorful and unusual features and most are unnamed. Caution should be exercised while exploring this vicinity since the ground is unstable and trails are not maintained. For anyone who wishes to see something truly spectacular Grand Prismatic Spring in Yellowstone National Park, Wyoming should be on the list. The hot spring is the third largest in the world, and the largest in the United States. For visitors to reach Grand Prismatic Spring one must drive to Midway Geyser Basin. This basin is located on the same loop at Old Faithful.
The spring was first found by European explorers in 1839. They were part of the American Fur Company walking through the country to find animals to trap for fur. One of the explorers made a note of the “boiling lake” stating its diameter was 300 feet. In 1870 the lake was truly made noteworthy when the Washburn-Langford- Doane Expedition entered the area. They also wrote about the area noting the 50 foot Excelsior. First discovered in the early 1800’s amidst the geysers and sulfurous bubblings of Yellowstone National Park, the record setting natural wonder has been stunning visitors for over a century. The pool is a piercing blue surrounded by rings of color ranging from red to green. The otherworldly effect is caused by varieties of pigmented bacteria and microbes that thrive in the warm, mineral abundant waters surrounding the hot spring. Changing along with the seasons the colors fade and grow more deep depending on what type of bacteria is thriving in the weather at the time. The center of the pool, where the water boils up from underground is so hot that the water is actually sterile. This produces a shockingly clear and bold blue color that the spring maintains year-round.
The Grand Prismatic Spring is one of America’s more beautiful sites to look at, just don’t touch as the boiling heat could likely melt skin from bone, mixing blood red into the deep blue.
Hot springs form when heated water emerges through cracks in the Earth’s surface. Unlike geysers, which have obstructions near the surface (hence their eruptions), water from hot springs flows unobstructed, creating a nonstop cycle of hot water rising, cooling and falling. In the Grand Prismatic Spring, this constant cycle creates rings of distinct temperatures around the center: very, very hot water bubbles up from the middle and gradually cools as it spreads out across the spring’s massive surface (370 feet across).
Water at the center of the spring, which bubbles up 121 feet from underground chambers, can reach temperatures around 189 degrees Fahrenheit, which makes it too hot to sustain most life (some life does manage to exist, but its limited to organisms that feed off of inorganic chemicals like hyrdogen gas). Because there’s very little living in the center of the pool, the water looks extremely clear, and has a beautiful, deep-blue color (thanks to the scattering of blue wavelengths—the same reason oceans and lakes appear blue to the naked eye). But as the water spreads out and cools, it creates concentric circles of varying temperatures—like a stacking matryoshka doll, if each doll signified a different temperature. And these distinct temperature rings are key, because each ring creates a very different environment inhabited by different types of bacteria. And it’s the different types of bacteria that give the spring its prismatic colors.
Within these rings live different organisms, including cyanobacteria, a type of bacteria that obtain their energy through photosynthesis. Look at the first band outside of the middle—see that yellow color? That’s thanks to a particular type of cyanobacteria, Synechococcus, that lives in that particular temperature band under extreme stressors. The temperature of that water is just barely cool enough to be habitable, at 165° F, but the bacteria prefer temperatures nearer to 149° F. But an abundance of light also introduces stress to the Synechococcus habitat.
Temperature 147-188°F Dimensions 250×380 feet. Grand Prismatic is the largest hot spring in Yellowstone, and is considered to be the third largest in the world-New Zealand has the two largest springs. Grand Prismatic sits upon a wide, spreading mound where water flows evenly on all sides forming a series of small, stair-step terraces. The Hayden Expedition in 1871 named this spring because of its beautiful coloration, and artist Thomas Moran made water-color sketches depicting its rainbow-like colors. The sketches seemed exaggerations and geologist A.C. Peale returned in 1878 to verify the colors. The colors begin with a deep blue center followed by pale blue. Green algae forms beyond the shallow edge. Outside the scalloped rim a band of yellow fades into orange. Red then marks the outer border. Steam often shrouds the spring which reflects the brilliant colors. Grand Prismatic discharges an estimated 560 gallons per minute.
Visitors who wish to see Grand Prismatic Spring will find the entrance to the spring closest to the west entrance of the park. Visitors can pay $25 per vehicle or $12 per person to enter the National Park and explore the entire park. At Grand Prismatic Spring there is a wooden walkway that takes visitors over the earth, close to the bacteria and spring to get a truly decent view of it. Photos can be taken on the walkway with the steam rising from the spring and the orange bacteria edging closer to the walkway. Surrounding the spring are small rolling hills and mountains. These are in the distance and littered with pine trees adding lush green colors to the view of the spring.