are the main attraction of the Mammoth District. These features are quite different from thermal areas elsewhere in the park. Travertine formations grow much more rapidly than sinter formations due to the softer nature of limestone. As hot water rises through limestone, large quantities of rock are dissolved by the hot water, and a white chalky mineral is deposited on the surface.
Although visitors are sometimes confused by the rapidly shifting activity of the hot springs and disappointed when a favorite spring appears to have died, it is important to realize that the location of springs and the rate of flow changes daily , that on-again-off-again is the rule, and that the overall volume of water discharged by all of the springs fluctuates little.
The North Entrance Road from Gardiner, Montana, to Mammoth Hot Springs, Wyoming, runs along the Gardner River. The road winds into the park, up the canyon, past crumbling walls of sandstone and ancient mudflows. The vegetation is much thicker in the canyon than on the open prairie down below, the common trees being Rocky Mountain juniper, cottonwood, and Douglas-fir. Low-growing willows also crowd the river's edge in the flatter, flood-prone sections of the canyon.
Watch for wildlife in season: eagles, osprey, dippers, and kingfishers along the river and bighorn sheep in the steeper parts of the canyon.
The 45th parallel is an imaginary line that circles the globe halfway between the equator and the North Pole. This same line passes through Minneapolis-St. Paul, Ottawa, Bordeaux, Venice, Belgrade, and the northern tip of the Japanese islands. It is, here in Yellowstone, roughly aligned with the Montana-Wyoming border.
A parking area on the east side of the road is used by bathers in the Boiling River. Bathers must walk upstream about a half mile from the parking area to the place where the footpath reaches the river. This spot is also marked by large clouds of steam, especially in cold weather. Here, a large hot spring, known as Boiling River, enters the Gardner River. The hot and the cold water mix in pools along the river's edge. Bathers are allowed in the river during daylight hours only. Bathing suits are required, and no alcoholic beverages are allowed. Boiling River is closed in the springtime due to hazardous high water and often does not reopen until mid-summer.
Mt. Everts is made up of distinctly layered sandstones and shales--sedimentary rocks deposited when this area was covered by a shallow inland sea, 70 to 140 million years ago.
Bunsen Peak is 8,564 feet high (2,612 meters) and may be climbed via a trail that starts at the Golden Gate. Another trail, the old Bunsen Peak road, skirts around the flank of the peak from the YCC camp to the Golden Gate. This old road may be used by hikers, mountain-bikers, and skiers in winter.