Yellowstone (USA)

Surface water seeps underground, is heated by a deep source of mama and rises as superheated water. Geysers occur when underground constrictions increase the pressure of the water until it finally erupts. Hot springs have no constrictions, so water rises, cools and sinks. The small amount of water in fumaroles flashes into steam before reaching the surface. Mudpots are acidic hot springs with limited water. The acid and microorganisms decompose surrounding rock into clay and mud. A main route to Old Faithful is from the south by way of Jackson, Wyo.,`and the South entrance. The park road crosses the continental Divide three times; waters flow east of it to the Atlantic Ocean or West to the Pacific Ocean. This route passes five geyser basins -- West Thumb, Upper (old Faithful), Midway, Lower and Norris – on the way to Mammoth Hot Springs. Sampling the world’s largest concentration of geysers you follow the Firehole and Gibbon rivers. A visitor Center at Old Faithful and museums at Norris tell aspects of the park’s stories.

Old faithful Geyser is the world’s best known geyser. Its eruption intervals have varied from 40 to 126 minutes. At Biscuit Basin mineral deposits took biscuit shapes, but an earthquake in 1959 triggered changes destroying the biscuits. At Midway Geyser Basin you may walk to Excelsior Geyser Crater and Grand Prismatic Spring. Firehole Lake Drive (one way north-bound) loops off the main road to Great, Fountain Geyser, Firehole Lake and a variety of hot pools . Lower Geyser Basin features Fountain Paint pot. Firehole canyon Drive (one way loop, southbound), starting south of Madison Junction, passes Firehole Falls. Roadside forests are mainly lodgepole pine. Some areas were burned in by wildfire in 1988. Norris Geyser Basin’s array of thermal features is unparalleled. Steamboat Geyser, the world’s tallest, erupts at irregular intervals of days to years. Porcelain Basin is the park’s hottest exposed area. Two miles south of Mammoth Hot Springs the Upper Terrace Drive passes through a thermal area. Gnarled limber pines on some dormant formations are over 500 years old. At mammoth Hot Springs the travertine (calcium carbonate) forms spectacular terraces. Yellowstone Lake is North America’s largest mountain lake. It now drains into the Atlantic via the Gulf of Mexico. The lake is 20 miles long, 14 miles wide and 430 feet deep at its deepest point. Swimming is discouraged even where not prohibited; such cold waters can cause potentially fatal hypothermia or hyperventilation within mere minutes.

West Thumb and Grant Village: Walk the board walk through the geyser basin at lake’s edge at West Thumb. Intense heat measured in lake sediments below West Thumb indicates a shallow thermal system underlying this more recent caldera within the Yellowstone caldera.