🌋VolcanoAtlas

Yellowstone Caldera

Earth's Most Famous Supervolcano

Elevation

2,805 m

Last Eruption

~70,000 years ago (lava flow)

Type

Caldera (Supervolcano)

Country

United States

Location

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Volcanic Hazards & Risk Assessment

Primary Hazards

  • Pyroclastic flows and surges
  • Large explosive eruptions (VEI 4+)
  • Ash fall and tephra deposits
  • Lahars and debris flows

Risk Level

Population at RiskModerate
Infrastructure RiskHigh
Aviation RiskSignificant

Geological Composition & Structure

Rock Types

Primary
Unknown
Silica Content
Varied composition

Tectonic Setting

Unknown
Intraplate setting with hotspot or regional volcanic activity.

Age & Formation

Epoch
Unknown
Evidence
Unknown

Eruption Statistics & Analysis

MetricValueGlobal RankingSignificance
Total Recorded EruptionsUnknownLowModerately active volcano
Maximum VEIVEI UnknownMinorLocal impact potential
Recent Activity-67974 years agoVery RecentCurrently active

Monitoring & Alert Status

Monitoring Networks

USGS Volcano Hazards Program
Comprehensive monitoring network
Global Volcanism Program
International eruption database

Current Status

Active
Recent volcanic activity detected. Continuous monitoring in place.

Authority Sources

Smithsonian GVP
Official volcano database
USGS Volcano Hazards
U.S. Geological Survey

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Interesting Facts

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Yellowstone's Huckleberry Ridge eruption (~2.1 million years ago) ejected approximately 2,500 km³ of material — enough to bury the entire state of Texas under 1.5 m of volcanic debris.

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The Yellowstone Caldera is so large (72 × 55 km) that its true extent was not recognized until satellite imaging and geological mapping in the 1960s and 1970s.

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Yellowstone contains more than 10,000 geothermal features — roughly half of all the active geothermal features on Earth.

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The park has more than 500 active geysers, more than any other region on the planet. Old Faithful erupts approximately every 90 minutes with remarkable regularity.

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The USGS estimates the annual probability of a caldera-forming Yellowstone supereruption at approximately 1 in 730,000 — lower than the probability of a 1-km asteroid impact.

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Yellowstone's mantle plume has been active for at least 16.5 million years, leaving a 650-km trail of progressively older calderas across the Snake River Plain.

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The extremophile bacterium Thermus aquaticus, discovered in Yellowstone's hot springs in 1969, provided the Taq polymerase enzyme that made PCR (polymerase chain reaction) possible — revolutionizing genetics and medicine.

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Grand Prismatic Spring, at 112 m (370 ft) in diameter, is the largest hot spring in the United States and the third largest in the world.

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Yellowstone's caldera floor rises and falls by several centimeters per year due to fluctuations in the underlying magma system — a phenomenon called 'caldera breathing.'

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The shallow magma chamber beneath Yellowstone contains only 5–15% molten material — it is not the roiling lake of lava depicted in popular disaster films.

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The 1959 Hebgen Lake earthquake (M7.3) near the park boundary killed 28 people and dramatically altered many of Yellowstone's geothermal features — some geysers became dormant while new ones activated.

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Yellowstone was the world's first national park, established by President Ulysses S. Grant in 1872 — 18 years before Wyoming even became a state.

Frequently Asked Questions

Is Yellowstone about to erupt?
Yellowstone is not showing signs of an imminent eruption. The Yellowstone Volcano Observatory continuously monitors the system with seismographs, GPS, satellite radar, and geochemical sensors. The current volcanic alert level is 'Normal' (green), indicating background activity. While the caldera experiences 1,500–2,500 small earthquakes per year and ongoing ground deformation, these are typical behaviors for a large volcanic system and do not indicate an approaching eruption. The USGS has stated that any future large eruption would be preceded by weeks to months of detectable precursors — intensifying earthquakes, accelerating ground uplift, and changes in gas emissions — that current instruments would identify.
What would happen if Yellowstone erupted today?
The impact depends entirely on eruption type. The most likely scenario — a hydrothermal explosion or lava flow — would primarily affect areas within the park. A full VEI 8 supereruption, while extremely unlikely (approximately 1 in 730,000 annual probability), would deposit thick pyroclastic material within 60–80 km, blanket states within 500 km in more than 30 cm of ash, disrupt agriculture across North America, ground air traffic, and inject enough sulfur dioxide into the stratosphere to cool global temperatures by 5–10°C for several years. However, most volcanologists consider a smaller eruption far more probable than a caldera-forming event.
When did Yellowstone last erupt?
Yellowstone's most recent volcanic eruption was a rhyolitic lava flow known as the Pitchstone Plateau flow, which occurred approximately 70,000 years ago. The most recent caldera-forming supereruption occurred approximately 640,000 years ago, producing the Lava Creek Tuff. The most recent explosive event was a large hydrothermal explosion that created the 2.6-km-wide Mary Bay crater on Yellowstone Lake approximately 13,000 years ago. Hydrothermal explosions, while not magmatic eruptions, are the most common type of violent event at Yellowstone and occur on timescales of centuries.
Is Yellowstone the biggest volcano in the world?
Yellowstone is one of the largest volcanic systems on Earth, but the title depends on how size is measured. By caldera area (72 × 55 km), it is one of the largest active calderas. However, by total volume, Mauna Loa in Hawaii is the world's largest active volcano, and Tamu Massif in the Pacific (now extinct) is the largest known volcano by volume. By eruption size, Yellowstone's Huckleberry Ridge eruption (~2,500 km³) ranks among the largest known, though the La Garita Caldera eruption in Colorado (~5,000 km³, ~27 Ma) was larger. Yellowstone is unquestionably the most powerful active volcanic system in North America.
How is Yellowstone monitored?
The Yellowstone Volcano Observatory (YVO) — a partnership between the USGS, University of Utah, and Yellowstone National Park — operates one of the most comprehensive volcano monitoring networks in the world. It includes more than 40 seismograph stations detecting earthquakes, more than 20 continuous GPS stations measuring ground deformation, satellite-based InSAR tracking surface changes, geochemical monitoring of gas emissions (particularly CO₂ and helium isotopes in thermal features), stream gauges and temperature sensors throughout the hydrothermal system, and regular field surveys. Data is analyzed in real time, and the alert level is published continuously.
Why does Yellowstone have so many geysers?
Yellowstone hosts more than 500 active geysers — over 60% of the world's total — because of a rare combination of three factors: a shallow heat source (the magma chamber 5–17 km below), abundant groundwater from snowmelt and rainfall across the high plateau, and a fractured rhyolitic rock 'plumbing system' that channels superheated water upward through constrictive passages. This plumbing geometry is critical — geysers require narrow conduits that allow pressure to build until the water flashes to steam explosively. Most volcanic areas lack this specific rock structure, which is why geysers are far rarer than hot springs globally.
Can you visit the Yellowstone Caldera?
Yes. Yellowstone National Park — which encompasses the caldera — receives approximately 4.5 million visitors per year. Major geothermal attractions include Old Faithful, Grand Prismatic Spring, Norris Geyser Basin, and Mammoth Hot Springs, all accessible via boardwalks. The park offers more than 1,600 km of hiking trails, campgrounds, lodges, and visitor centers. Entry costs $35 per vehicle for seven days. Peak season is July–August; September is less crowded with excellent wildlife viewing. All visitors must stay on designated boardwalks in thermal areas — the ground can be thin crust over boiling water.
What type of volcano is Yellowstone?
Yellowstone is classified as a caldera — a large volcanic depression formed by the collapse of ground following a massive eruption that empties or partially empties the underlying magma chamber. It belongs to a special category informally called a supervolcano, meaning it is capable of producing eruptions of VEI 8 (more than 1,000 km³ of ejecta). Unlike the conical shape of stratovolcanoes such as Mount Fuji, calderas are broad, often subtle depressions. Yellowstone sits above an intraplate hotspot rather than a subduction zone, making its tectonic setting similar to Hawaii but with fundamentally different (rhyolitic vs. basaltic) magma composition.