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Windows into the EarthThe Geologic Story of Yellowstone and Grand Teton National Parks$
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Robert B. Smith and Lee J. Siegel

Print publication date: 2000

Print ISBN-13: 9780195105964

Published to Oxford Scholarship Online: November 2020

DOI: 10.1093/oso/9780195105964.001.0001

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PRINTED FROM OXFORD SCHOLARSHIP ONLINE (oxford.universitypressscholarship.com). (c) Copyright Oxford University Press, 2021. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 21 June 2021

How Yellowstone Works

How Yellowstone Works

(p.65) 4 How Yellowstone Works
Windows into the Earth

Robert B. Smith

Lee J. Siegel

Oxford University Press

Most people who visit Yellowstone are blissfully unaware they are standing on top of an active, breathing volcano. They visit geysers and hot springs, and may feel some of the numerous earthquakes that rattle the region. Few realize the seemingly solid ground beneath them is slowly stretching apart and huffing and puffing upward and downward. Nor are many visitors aware of the large chamber of molten and partially molten rock several miles beneath their feet, or of the even deeper plume of hot rock moving up from deep within Earth. Indeed, it is easy to enjoy the national park’s geysers and other scenery without stopping to consider they are merely the uppermost, most visible parts of one of the world’s geological wonders: the Yellowstone hotspot. Even fewer tourists realize the same forces driving Yellowstone’s renowned geysers also reshaped the landscape of 25 percent of the northwestern United States—a broad band stretching from Yellowstone almost 500 miles southwest to the Idaho—Oregon—Nevada border. As North America drifted southwest over the hotspot during the past 16.5 million years, the immense heat and molten rock rising from Earth’s mantle melted, rearranged, and blew apart the overlying crust. Today, the hotspot is beneath Yellowstone, making the national park a field laboratory of active geologic process: volcanism, earthquakes, faulting, and large-scale movement and deformation of Earth’s crust. Let us examine how this system works—how heat and magma, or molten rock, from within the Earth drive small-scale features such as geysers and hot springs, contribute to the most intense earthquake and volcanic activity in the Rocky Mountains, and help mold the topography of the region. The amount of heat flowing from the ground in the Yellowstone caldera is thirty to forty times more than the heat emitted by an average piece of ground elsewhere on Earth’s continents. This enormous heat flow provides the energy that melted rock under the caldera and helped lift Yellowstone to its lofty altitude. Heat powers Yellowstone’s volcanic activity by melting rock in Earth’s mantle and crust. In turn, the molten rock heats groundwater to produce geysers and hot springs.

Keywords:   Brine, Calcite Springs, Dome Geyser, Earthquake swarms, Fishing Bridge, Gallatin fault, Hayden Valley, Lower Geyser Basin, Madison Range

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