World+Book+Online

Yellowstone National Park, the oldest national park in the world, is famous for its many natural wonders. The park has more geysers and hot springs than any other area in the world. Yellowstone's scenic attractions include deep canyons, thundering waterfalls, sparkling lakes, and vast evergreen forests broken by rolling meadows. Yellowstone is also one of the largest wildlife preserves in the United States. It has a greater concentration of large and small animals than any other area in the United States except Alaska. Bears, elk, and bison (American buffaloes) roam the park, and bald eagles, trumpeter swans, and white pelicans nest there.

Yellowstone lies in the northwest corner of Wyoming and spreads into Idaho and Montana. The park covers 2,200,000 acres (898,000 hectares). A series of high plateaus extends across the park, and mountains rise along Yellowstone's northern, eastern, and western boundaries. The highest point, Eagle Peak, rises 11,358 feet (3,462 meters) in the Absaroka Range in the east. Most of Yellowstone's landscape was created by volcanic eruptions about 600,000 years ago. A large mass of molten rock still lies beneath the surface of the park. This rock, called magma, furnishes the heat for the park's geysers and hot springs. Yellowstone has more than 300 active geysers and thousands of hot springs.

The government established Yellowstone in 1872. It was named for the yellow rocks that lie along the part of the Yellowstone River that is north of the park. Over 2 1 /2 million people visit Yellowstone yearly. Most of them drive through the park, but many explore large wilderness areas that can be reached only by foot or on horseback. The park has more than 450 miles (725 kilometers) of roads and over 1,000 miles (1,600 kilometers) of trails.

The Lower Loop. The west entrance road joins the Lower Loop at Madison Junction. Southbound, the Lower Loop leads to several geyser basins. The Lower Geyser Basin includes the Fountain Paint Pots, a series of hot springs and bubbling pools of mud called mudpots or paintpots. The mudpots are formed by steam and other gases that rose from holes in the ground and changed the surrounding rock into clay. Minerals in the clay give the mud various colors. Great Fountain Geyser, also in the Lower Geyser Basin, erupts from the center of a large pool. The bursts of water from this geyser sometimes spout 200 feet (61 meters) above the pool. Grand Prismatic Spring, in Midway Geyser Basin, is the largest hot spring in Yellowstone. Its pool, which has a deep blue center ringed with pale blue, measures 370 feet (113 meters) in diameter. Small water organisms called algaegive the pool its color.

The Upper Geyser Basin has a large group of geysers. In most years, Old Faithful, the most famous geyser in the park, erupts about every 90 minutes. The actual intervals between eruptions vary from about 30 to 120 minutes. The geyser sends a stream of boiling water more than 100 feet (30 meters) into the air. Other geysers include Castle, Giantess, Grand, and Grotto. Morning Glory Pool, one of the basin's most beautiful hot pools, resembles the morning-glory flower in color and shape.

Yellowstone Lake, which lies 7,733 feet (2,357 meters) above sea level, is the largest high-altitude lake in North America. It measures about 20 miles (32 kilometers) long and 14 miles (23 kilometers) wide. The lake has a shoreline of about 110 miles (180 kilometers). Geysers and hot springs occur along the shore at West Thumb. The Lower Loop follows the shoreline for 21 miles (34 kilometers), providing a view of the lake's islands and the rugged mountains of the Absaroka Range. The Grand Canyon of the Yellowstone cuts across the landscape for about 20 miles (32 kilometers). This canyon reaches a depth of about 1,200 feet (370 meters) in some places. The Yellowstone River runs through the canyon, creating two waterfalls. The Lower Falls plunges 308 feet (94 meters) and the Upper Falls 109 feet (33 meters) into the canyon. Views of the canyon are especially beautiful from Artist Point, Grandview Point, and Inspiration Point. See

The Upper Loop leads north from Canyon with a climb through the mountains of the Washburn Range. Mount Washburn rises 10,243 feet (3,122 meters) on the east. Specimen Ridge, which can be seen from the road leading to the northeast entrance, has some of the park's most famous petrified forests. The trees there were buried during volcanic eruptions about 50 million years ago by mudflows and streams carrying suspended earth and ash. Minerals from the mud and water seeped into the trees and turned them into stone.

At Mammoth Hot Springs, beautiful terraces are formed by gently flowing waters. The waters deposit a form of limestone called travertine, building large terraces one above the other. Algae and bacteria give some terraces various colors. Minerva Terrace and Opal Terrace are among the most beautiful in the area. The terraces change through the years as the waters deposit calcium carbonate, a mineral that builds up the formations. Some springs die, and the terraces become gray and lifeless. The Hoodoos are the remains of old hot-spring terraces broken up by landslides. Obsidian Cliff is a mountain of black glass that was formed by molten lava. Rootless vegetation called lichens now cover the glass in many places. Norris Geyser Basin consists of hundreds of geysers, hot springs, and pools. It is the hottest and most active thermal area in Yellowstone. The temperature of the water in some of the springs reaches more than 400 °F (200 °C). Several geysers may erupt at the same time.

History Yellowstone's landscape was shaped by the action of volcanoes and glaciers through millions of years. A large mass of magma, which lies about 1 to 2 miles (1.6 to 3.2 kilometers) below the surface of the park, has erupted more than 27 times during the past 2 million years. A major volcanic eruption occurred in the Yellowstone area about 2 million years ago. About 600,000 years ago, another explosion of magma and gas created much of Yellowstone's present-day geography. The eruption produced the Yellowstone Caldera, which is a huge crater about 47 miles (76 kilometers) long and 28 miles (45 kilometers) wide. Yellowstone Lake now occupies part of this crater. Glaciers once covered much of the area. The last ones melted about 8,500 years ago and filled Yellowstone Lake. Outflow from the lake drained northward and helped shape the Grand Canyon of the Yellowstone.

Critically reviewed by Yellowstone National Park

MLA: "Yellowstone National Park." World Book Student. World Book, 2015. Web. 21 Sept. 2015.