At the heart of Yellowstone's past, present, and future lies volcanism. Catastrophic volcanic eruptions occurred here

• About 2 million years ago,
• then 1.2 million years ago,
• and then again 600,000 years ago.

 Old Faithful to Mammoth Hot Springs
One of the main routes to Old Faithful is from the south via Jackson, Wyoming, and the South Entrance. The park road crosses the Continental Divide three times. Waters flow east of the divide to the Atlantic, or west to the Pacific. This park route passes five geysers

• West Thumb,
• Upper (Old Faithful),
• Midway,
• Lower,
• and Norris

on its way to Mammoth Hot Springs. Sampling the world's largest concentration of geysers, you follow the beautiful Firehole and Gibbon rivers. A visitor center at Old Faithful and a museum at Norris tell aspects of the park story.

Old Faithful
Old Faithful Geyser is the world's best-known geyser. Its eruption intervals have long varied around an average of 65 minutes, ranging from 30 to 120 minutes. Recent earthquakes have lengthened the average interval to 78 minutes. Eruption times of other nearby geysers are available at the visitor center.

Old Faithful to Madison
 

• In Black Sand Basin the bright colors of Sunset Lake and Emerald Pool attract photographers.
• At Biscuit Basin, mineral deposits took on biscuit shapes before a 1959 earthquake 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, northbound) loops off the main road to Great Fountain Geyser, Firehole Lake, a hot pool, and the Three Senses Trail.
• The Lower Geyser Basin features the Fountain Paint Pots. Fountain Flat Drive exits west and ends at Goose Lake. Firehole Canyon loop drive (one way, southbound), starting south of Madison Junction, passes by Firehole Falls.

The museum at Madison Junction portrays the evolution of the national park idea. Roadside forests are mainly lodgepole pine, some reddened by the feeding of mountain pine beetles. West Yellowstone, Montana is 14 miles west of Madison Junction. From Madison to Norris you drive along the Yellowstone caldera's northwest rim. Gibbon Falls cascade over the caldera wall.

Norris Junction to Mammoth Hot Springs
Norris Geyser Basin's array of thermal features is unparallelled.

• Steamboat Geyser, the world's largest, erupts at irregular intervals of days to years.
• Echinus Geyser erupts about once per hour.
• Porcelain Basin is Yellowstone's hottest exposed area.

Exhibits at Norris Museum explain geyser workings.

At Norris Junction you can turn east toward the Canyon area. At Canyon you can go north to Tower Junction or south to the Lake Area.

• Continuing north of Norris you pass Obsidian Cliff. Obsidian, a volcanic glass excellent for projectile points and cutting tools, was traded across North America by Native Americans.
• Five miles south of Mammoth Hot Springs, at Swan Lake Flat's north end, a rough one-way dirt road goes around Bunsen Peak.
• Two miles south of Mammoth Hot Springs the Upper Terrace Loop Drive passes through a fascinating thermal area. Gnarled limber pine trees on some extinct formations are over 500 years old.
• At Mammoth Hot Springs the terraces are spectacular travertine (calcium carbonate) formations deposited daily. Most new rock from Yellowstone's geysers is called geyserite, a noncrystalline mineral chemically similar to glass. Exhibits at Albright Visitor Center portray the park's early history and wildlife and tell how the US Army protected the park from 1886 to 1916. Park headquarters is in the buildings of Fort Yellowstone, a late 19th-century cavalry post. Gardiner, Montana, lies five miles north. The Yellowstone River flows north, eventually to join the Missouri.

 To Tower Junction and Canyon
 

• The road east from Mammoth Hot Springs leads your four miles to Undine Falls, then 0.2 miles to Lava Creek.
• Three miles further east look for waterfowl and muskrats at Blacktail Ponds.
• Next, Blacktail Plateau Drive, a one-way dirt road eastbound, leaves the main road to traverse grass- and sagebrush-covered hills and forests of Douglas-fir, Engelmann spruce, and lodgepole pine. Watch for pronghorn antelope, mule deer, and elk. Scattered groves of quaking aspen trees turn gold in autumn.
• The next side road leads to a petrified redwood tree. Such trees may be found over hundreds of square miles in northern Yellowstone. Some are still in an upright position.

Tower Junction to Northeast Entrance
Lamar Valley, accessible all year, is winter range for elk and bison. You may camp at Slough Creek or Pebble Creek campgrounds en route to the Northeast Entrance, 29 miles from Tower Junction. Beyond lie Silver Gate (one mile) and Cooke City, Montana (four miles), and the Beartooth Highway climbs to 10,940 feet at Beartooth Pass.

Tower Junction to Canyon
 

• Tower Falls, tumbling 132 feet, was named for the adjacent volcanic pinnacles. Tower Creek flows into the Yellowstone River. South from Tower Falls, as you drive up Mount Washington, look east, downslope, into prime grizzly bear country on Antelope Creek. This area is closed to human travel, to offer the bears refuge.
  DO NOT ATTEMPT TO FEED OR APPROACH BEARS
  .
• The main road next crosses Dunraven Pass at 8,850 feet elevation, amidst broad-topped whitebark pines and spire-shaped subalpine fir. Meadows produce a profusion of wildflowers during the brief summer.
• From the Washburn Hot Springs Overlook south of the pass, you can see the Yellowstone caldera. Its north boundary is Mount Washburn and its south boundary is the Red Mountains 35 miles away. You can see the Teton Range on clear days, on the right beyond the Red Mountains.

  Canyon
  Because of bear activity here, camping is restricted to hard-sided units only. Exhibits at the Canyon Visitor Center explain the park's geology. A 2.5-mile loop road (one way) leads first to a spur road out to Inspiration Point. Here the Grand Canyon of the Yellowstone River plunges 1,000 feet below you. The canyon's colors were created by hot water acting on volcanic rock. It was not these colors, but the river's yellow banks at its distant confluence with the Missouri River, that occasioned the Minnetaree Indian name which French trappers translated as roche jaune, yellow stone. The canyon has been rapidly downcut more than once, perhaps by great glacial outburst floods. Little deepening takes place today.

  Grandview Point affords a distant view of the 308-foot Lower Falls. Lookout Point affords a vista of Lower Falls, and a steep trail descends to a closer viewpoint. Back on the main road turn left in 0.3 miles to view the brink of the 109-foot Upper Falls. Back on the main road again, go 0.6 miles south to Artist Point Road and cross Chittenden Bridge to Uncle Tom's Parking Area. Trails here offer close views of the Upper and Lower Falls. South Rim Drive leads to Artist Point for another view of the canyon and Lower Falls.

  Hayden Valley
  The road here follows the Yellowstone River's meanderings across a former lakebed. After the great glaciers retreated, Yellowstone Lake was much larger than it is today, and this area was then flooded. The lake left fine silt and impermeable clay soil that permits little tree growth but allows rich shrubland that provides food for a variety of wild animals. Waterfowl, including white pelicans and trum-peter swans, abound in marshy areas. In this open parkland you may see moose, bison, and occasionally grizzly bears.
  VIEW LARGE ANIMALS ONLY AT A DISTANCE, FROM YOUR CAR OR FROM ROAD-SIDES. Do not stop in roadways; use roadside parking areas for your safety.
  No fishing is allowed for a 6-mile section in Hayden Valley. This provides quiet for the animals and views of untrammeled wilderness scenery for you. Stop at Mud Volcano and see the varied thermal features there. You might see spawning cutthroat trout jumping at Le Hardy Rapids, 3 miles north of Lake Junction, in June and July.

  ---

   The Lake Area
  East Entrance to Fishing Bridge Junction
  Cody, Wyoming, lies 50 miles beyond the East Entrance. As you cross 8,530-foot elevation Sylvan Pass, watch for pikes and yellow-bellied marmots, illustrated above, in the rocky debris of talus slopes. You descend the west slope of the Absaroka Mountains, an eroded volcanic range named for the Crow Indians. Near Yellowstone Lake a spur road leads to Lake Butte Overlook for a view of this immense body of water. Yellowstone Lake occupies only the southeast quarter of the Yellowstone caldera. At the overlook you are 4 miles outside the caldera's east boundary. Just north of the lake the Earth's surface is rising about 0.9 inches per year! This suggests future volcanic activityhere. As you drive along the lake's edge, you can see Steamboat Springs. This is a hot spring remnant located on a line of faults, or fractures in the Earth, that also pass through Mary Bay and Indian Pond to the northwest. Bay and pond both occupy geologi-cally recent hydrothermal explosion craters. The bottom sediments in Mary Bay are still very warm. Watch for moose browsing in the sedge meadows and marshes along Pelican Creek flats as you approach Fishing Bridge.

  Exhibits at Fishing Bridge Museum feature the park's birds. Fishing Bridge itself spans the Yellowstone River, the lake's outlet. The bridge was closed to fishing in 1973. Fishing Bridge now offers one of the best wild trout spawning shows anywhere for most of the summer. White pelicans feed on the native cut-throat trout. Because of a high level of bear activity, only hard-sided units are allowed to camp in the Fishing Bridge area.

  Yellowstone Lake is North America's largest mountain lake. Over geological time it has drained into the Pacific Ocean, the Arctic Ocean via Hudson Bay, and now drains into the Atlantic via the Gulf of Mexico. It is 20 miles long, 14 miles wide, and 320 feet deep at its deepest point. The average depth is about 139 feet. Trout generally inhabit the upper 60 feet because their foods rarely occur below that depth. The average surface temperature in August is about 60°F, and the bottom temperature never rises above 42°F. Swimming is discouraged even where not prohibited: Such cold waters can cause potentially fatal hypothermia or hyperventilation in minutes.

  Boating is popular on some park lakes. Permits (required for all watercraft) and advice on canoeing and kayaking can be obtained at ranger stations at Lake Village or at Grant Village. A marina is at Bridge Bay and boat ramps are at Grant Village.

  Traveling toward West Thumb you may take a rough spur road, starting south of Bridge Bay, to see the natural bridge for which the area is named. Gull Point Drive loops off the Grand Loop Road for a closer view of the lake's edge.

  West Thumb and Grant Village
  Walk the boardwalk 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. Should the lake level fall just a few feet, an immense steam (hydrothermal) explosion could occur here. That is what created the craters now filled by Mary Bay and Indian Pond, described above. Exhibits at Grant Village Visitor Center, two miles south of West Thumb, feature the park's immense wilderness. Fishing, boating, and backcountry use permits are available at the ranger station.

The above information is derived from the National Park Service.

Yellowstone Net is Produced by Bruce Gourley, Russ Finley,  & Tim Gourley.
Copyright 1997-2007 by Bruce Gourley.