Grand Geyser is a fountain geyser

Geyser

A geyser is a spring characterized by intermittent discharge of water ejected turbulently and accompanied by a vapour phase . The word geyser comes from Geysir, the name of an erupting spring at Haukadalur, Iceland; that name, in turn, comes from the Icelandic verb geysa, "to gush", the verb...

 in the Upper Geyser Basin of Yellowstone National Park

Yellowstone National Park

Yellowstone National Park, established by the U.S. Congress and signed into law by President Ulysses S. Grant on March 1, 1872, is a national park located primarily in the U.S. state of Wyoming, although it also extends into Montana and Idaho...

 in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. It is the tallest predictable geyser known. It was named by Dr. F.V. Hayden

Ferdinand Vandeveer Hayden

Dr. Ferdinand Vandeveer Hayden was an American geologist noted for his pioneering surveying expeditions of the Rocky Mountains in the late 19th century. He was also a physician who served with the Union Army during the Civil War.-Early life:Ferdinand Hayden was born in Westfield, Massachusetts...

 in 1871.

Eruptions

Grand's fountain reaches a height of as much as 200 feet (61 m), with a duration of 9 to 12 minutes. Its eruptions occur in a series of 1 to 4 (rarely as many as 5) bursts.

Sequence

Grand erupts every 7 to 15 hours. It belongs to the Grand Group (or Grand Geyser Complex), and its eruption is connected to those of the other geysers in the group, especially the adjacent Vent Geyser

Vent Geyser

Vent Geyser is a geyser in the Upper Geyser Basin of Yellowstone National Park in the United States.Vent Geyser belongs to the Grand Group , and its eruption is tied to Grand Geyser. Normally, it erupts immediately after Grand and continues to erupt intermittently for about an hour afterward along...

 and Turban Geyser

Turban Geyser

Turban Geyser is a geyser in the Upper Geyser Basin of Yellowstone National Park in the United States.Turban Geyser belongs to the Grand Group , and its eruption is tied to Grand Geyser. In the hours prior to Grand's eruption, Turban will have five minute eruptions every 15–25 minutes. These...

.

For a few hours before an eruption by Grand, Turban Geyser erupts for a duration of five minutes about every 20 minutes. Grand's eruption begins within 1 to 2 minutes of one of Turban's eruptions with Vent Geyser erupting shortly after Grand. On occasions, Grand will stop erupting after 8 minutes only to restart with a taller fountain a minute or two later. Grand has been known to rarely experience over half a dozen restarts in a single eruption period. After Grand ceases its eruption, Vent and Turban continue erupting for another hour.

Upon the finish of an eruption, Grand's pool is empty and takes about five hours to refill.