The Snake River Plain and the Yellowstone Hot Spot
The geysers, hot springs, and bubbling mud pots of Yellowstone National
Park indicate there is extra heat beneath this corner of Wyoming.
Geologists and volcanologists think the heat is from a hot spot beneath
Yellowstone. A long line of features that extends to the west from
Yellowstone are interpreted to be the track left in the continent from
the hotspot. Most of these features are part of the Snake River Plain.
The Snake River Plain extends 400 miles (650 km) westward from northwest
Wyoming to the Idaho-Oregon border. The Snake River Plain is a broad,
flat arcuate depression which is concave to the north and covers one
quarter of the state of Idaho. Elevations on the Snake River Plain
decrease from the east (4,400-5,000 feet; 1,350-1,525 m) to the west
(2,950-3,900 feet; 900-1,200 m). Some features within the Snake River
Plain become younger to the east. For example, calderas become
progressively younger from west to east. The Yellowstone calderas are
they youngest and mark the approximate location of the hotspot.
Yellowstone has had three very large eruptions in the last 2 million
years. During each event, a large volume of
rhyolite magma was erupted
from a shallow level in the crust and a large
caldera formed. These
eruptions occurred 2.0, 1.3, and 0.6 million years ago. The volume of
lava erupted makes the 1980 eruption of Mount St. Helens look very small.
Seismologists, scientists that study earthquakes, think they have
detected the path the magma follows from the hot spot to shallow levels
beneath Yellowstone. They used earthquake waves. The waves travel
fastest in cold, dense rock. In warmer, less dense rocks, the waves slow
down. A zone of warmer rocks has been mapped beneath Yellowstone.
Visit Yellowstone National Park.
Sources of Information
Christiansen, 1984, Yellowstone magmatic evolution: its bearing on
understanding large-volume explosive volcanism, in Boyd, F.R., ed.,
Explosive volcanism: Inception, evolution, and hazards: National Research
Council Studies in Geophysics, Washington, D.C., National Academy Press,
Newhall, C.G., and Dzurisin, D., 1988, Historical unrest at large
calderas of the world: U.S. Geological Survey Bulletin 1855, v. 2, p.
Smith, R. B., and L. W. Braile, 1994, The Yellowstone Hotspot, in J.
Volcanology and Geotherm. Resesarch, eds. D.P. Hill, P. Gasparini, S.
McNutt and H. Rymer, H., 61:121-188.
Smith, R.B., and Braile, L.W., 1983, Crustal structure and evolution of
an explosive silicic volcanic system at Yellowstone National Park, in
Boyd, F.R., ed., Explosive volcanism: Inception, evolution, and hazards:
National Research Council Studies in Geophysics, Washington, D.C.,
National Academy Press, p. 96-109.