Natural Hazards

The most recent volcanic activity at Yellowstone consisted of rhyolitic lava flows that erupted approximately 70,000 years ago. The largest of these flows formed the Pitchstone Plateau in southwestern Yellowstone National Park.Learn more:Yellowstone Eruption HistoryThe evolution of the Yellowstone Plateau Volcani Field: Past, present, and future!

Almost all earthquakes at Yellowstone are brittle-failure events caused when rocks break due to crustal stresses. Though we've been looking at Yellowstone for years, no one has yet identified "long-period (LP) events" commonly attributed to magma movement. If LP events are observed, that will NOT mean Yellowstone is getting ready to erupt. LP earthquakes commonly occur at other volcanoes in the...

Contrary to popular belief, Yellowstone was not named for the abundant rhyolite lavas in the Grand Canyon of Yellowstone that have been chemically altered by reactions with steam and hot water to create vivid yellow and pink colors. Instead, the name was attributed as early as 1805 to Native Americans who were referring to yellow sandstones along the banks of the Yellowstone River in eastern...

Yellowstone is underlain by two magma bodies. The shallower one is composed of rhyolite (a high-silica rock type) and stretches from 5 km to about 17 km (3 to 10 mi) beneath the surface and is about 90 km (55 mi) long and about 40 km (25 mi) wide. The chamber is mostly solid, with only about 5-15% melt. The deeper reservoir is composed of basalt (a low-silica rock type) and extends from 20 to 50...

Yellowstone Volcano is monitored for signs of volcanic activity. The Yellowstone Volcano Observatory (YVO), is a partnership between the U.S. Geological Survey (USGS), Yellowstone National Park, the University of Utah, the University of Wyoming, UNAVCO, the Montana Bureau of Mines and Geology, the Idaho Geological Survey, and the Wyoming State Geological Survey. YVO closely monitors volcanic...

Since the most recent giant (caldera-forming) eruption 631,000 years ago, approximately 80 relatively nonexplosive eruptions have occurred. Of these eruptions, at least 27 were rhyolite lava flows in the caldera, 13 were rhyolite lava flows outside the caldera, and 40 were basalt vents outside the caldera. The most recent volcanic eruption at Yellowstone, a lava flow on the Pitchstone Plateau...

Yellowstone is not overdue for an eruption. Volcanoes do not work in predictable ways and their eruptions do not follow predictable schedules. Even so, the math doesn’t work out for the volcano to be “overdue” for an eruption. In terms of large explosions, Yellowstone has experienced three at 2.08, 1.3, and 0.631 million years ago. This comes out to an average of about 725,000 years between...

The most likely explosive event to occur at Yellowstone is actually a hydrothermal explosion—a rock-hurling geyser eruption—or a lava flow. Hydrothermal explosions are very small; they occur in Yellowstone National Park every few years and form a crater a few meters across. Every few thousand years, a hydrothermal explosion will form a crater as much as a few hundred meters across.Though the worst...

The diagram below shows that the three largest Yellowstone eruptions emitted much more material than the eruptions of Mount St. Helens (1980), Mount Pinatubo in the Philippines (1991), Krakatau in Indonesia (1883, incorrectly known as Krakatoa), and Tambora in Indonesia (1815).The largest eruption in the last two million years was about 74,000 years ago at Toba Volcano on the island of Sumatra...

The science of forecasting a volcanic eruption has significantly advanced over the past 25 years. Most scientists think that the buildup preceding a catastrophic eruption would be detectable for weeks and perhaps months to years. Precursors to volcanic eruptions include strong earthquake swarms and rapid ground deformation and typically take place days to weeks before an actual eruption...

Actually, the source of the hotspot is more or less stationary at depth within the Earth, and the North America plate moves southwest across it. The average rate of movement of the plate in the Yellowstone area for the last 16.5 million years has been about 4.6 centimeters (1.8 inches) per year. However, if shorter time intervals are analyzed, the plate can be inferred to have moved about 6.1...

Yellowstone is a plateau high in the Rocky Mountains, and is snowbound for over six months per year. The mean annual temperature is 2.2°C (36°F), barely above the freezing point of water. However, Yellowstone is also an active geothermal area with hot springs emerging at ~92°C (~198°F) (the boiling point of water at Yellowstone's mean altitude) and steam vents reported as high as 135°C (275°F)...