Volcanoes in the United States

The United States has 165 Holocene volcanoes — more than any other country on Earth — spread across an extraordinary range of tectonic environments from the Aleutian Islands of Alaska to the tropical shield volcanoes of Hawaii and the submarine vents of the Mariana Arc. This vast volcanic inventory includes 89 [[special:types-of-volcanoes|stratovolcanoes]], 24 volcanic fields, 17 shield volcanoes, and 4 calderas, among other types. At least 62 of these volcanoes have produced historically observed eruptions, and 25 have erupted since the year 2000, making the United States one of the most volcanically active nations in the world.

The country's volcanic landscape is shaped by three primary tectonic mechanisms. Along the northern Pacific margin, the Pacific Plate subducts beneath the North American Plate, generating the explosive stratovolcanoes of the [[special:ring-of-fire|Ring of Fire]] that run from the Aleutian Ridge through the Alaska Peninsula and into the Cascade Range of Washington, Oregon, and California. In the central Pacific, the Hawaiian hotspot — a deep mantle plume — has built the largest shield volcanoes on Earth, including [[volcano:mauna-loa|Mauna Loa]] and [[volcano:kilauea|Kilauea]].

And across the western interior, Basin and Range extension and the Yellowstone hotspot have created volcanic fields, calderas, and fissure vents stretching from Idaho to New Mexico.

The United States Geological Survey's [[ext:https://www.usgs.gov/programs/VHP|Volcano Hazards Program]] monitors 161 potentially active U.S. volcanoes through five regional volcano observatories: the Alaska Volcano Observatory (AVO), the Cascades Volcano Observatory (CVO), the Hawaiian Volcano Observatory (HVO), the Yellowstone Volcano Observatory (YVO), and the California Volcano Observatory (CalVO). The 1980 eruption of [[volcano:st-helens|Mount St. Helens]] remains the deadliest and most economically destructive volcanic event in U.S. history, while the 1912 eruption of [[volcano:novarupta|Novarupta]] in Alaska was the largest volcanic eruption anywhere in the world during the 20th century.

The United States owes its extraordinary volcanic diversity to its position at the intersection of several major tectonic processes. No other country spans as many distinct volcanic settings.

The dominant mechanism is subduction. Along the Aleutian Trench, the Pacific Plate descends beneath the North American Plate at approximately 7.5 cm per year, generating the 2,500 km arc of the Aleutian Islands — a chain of 46 stratovolcanoes that represents the densest concentration of active volcanoes in the United States. This subduction continues along the Alaska Peninsula, where 27 additional volcanoes have formed above the down-going slab.

Further south, the Juan de Fuca and Gorda Plates subduct beneath the Pacific Northwest, creating the Cascade Volcanic Arc — home to iconic peaks like [[volcano:rainier|Mount Rainier]], [[volcano:st-helens|Mount St. Helens]], Mount Hood, and [[volcano:shasta|Mount Shasta]]. These Cascade volcanoes tend to produce intermediate to silicic magmas that drive highly explosive eruptions.

The second major mechanism is hotspot volcanism. The Hawaiian Islands sit above one of Earth's best-studied mantle plumes, a stationary column of hot rock rising from deep in the mantle. As the Pacific Plate moves northwest at roughly 7 cm per year over this plume, a conveyor belt of volcanic islands has formed over the past 80 million years.

The currently active volcanoes — Kilauea, Mauna Loa, and the submarine Kamaʻehuakanaloa (formerly Loihi Seamount) — sit directly above the plume, producing basaltic eruptions that are typically effusive rather than explosive. The Yellowstone hotspot beneath the continental interior operates on a similar principle, though its interaction with thick continental crust produces far more explosive silicic volcanism.

The third mechanism involves extensional tectonics in the Basin and Range Province, where the North American Plate is being stretched thin. This rifting has generated volcanic fields across Nevada, Utah, Arizona, New Mexico, and parts of Oregon, including Craters of the Moon in Idaho and the San Francisco Volcanic Field in Arizona. Though less dramatic than subduction volcanism, these fields can produce eruptions with little warning — the most recent Basin and Range eruption, at Sunset Crater near Flagstaff, occurred around 1075 CE.

Finally, the U.S. territory of the Northern Mariana Islands adds 25 volcanic centers along the Mariana Arc in the western Pacific, where the Pacific Plate subducts beneath the Philippine Sea Plate in the deepest ocean trench on Earth. Though remote and largely submarine, these volcanoes are capable of significant eruptions — [[volcano:anatahan|Anatahan]] erupted as recently as 2008, and [[volcano:ahyi|Ahyi Seamount]] showed activity in 2025.

**Kilauea** — The world's most active shield volcano, [[volcano:kilauea|Kilauea]] rises to just 1,247 m (4,091 ft) on the southeastern flank of Mauna Loa on the Big Island of Hawaii. With 75 confirmed eruptions in the historical record and continuous activity between 1983 and 2018 at the Puʻu ʻŌʻō vent, Kilauea has produced more lava in the past 250 years than any other volcano on Earth. The dramatic 2018 lower East Rift Zone eruption destroyed over 700 homes in the Leilani Estates subdivision and drained the summit lava lake entirely.

Kilauea resumed erupting in 2020 and was active again in 2025.

**Mauna Loa** — Rising 4,170 m (13,681 ft) above sea level and roughly 9,170 m from its base on the ocean floor, [[volcano:mauna-loa|Mauna Loa]] is the largest active volcano on Earth by volume, containing an estimated 75,000 km³ of rock. It last erupted in November–December 2022 after 38 years of quiet, sending lava flows down its Northeast Rift Zone that came within a few kilometers of the Saddle Road. With 110 confirmed eruptions, Mauna Loa is also one of the most frequently active volcanoes in the United States.

**Mount St. Helens** — The most famous volcano in the contiguous United States, [[volcano:st-helens|Mount St. Helens]] in Washington State is a 2,549 m (8,363 ft) [[special:types-of-volcanoes|stratovolcano]] that produced the catastrophic eruption of May 18, 1980 — a VEI 5 event that killed 57 people, triggered the largest landslide in recorded history, and blasted 600 km² of forest flat.

With 40 confirmed eruptions and a maximum VEI of 6, St. Helens is the most explosively active Cascade volcano in the Holocene. A dome-building episode from 2004 to 2008 was its most recent activity.

**Mount Rainier** — At 4,392 m (14,411 ft), [[volcano:rainier|Mount Rainier]] is the tallest volcano in the Cascade Range and is considered one of the most dangerous volcanoes in the United States. Its 26 glaciers contain more ice than all other Cascade volcanoes combined, and this ice represents a catastrophic lahar hazard: USGS modeling shows that a major lahar could reach the Puget Sound lowlands — home to over 100,000 people in former lahar inundation zones — within one to two hours. Rainier last erupted around 1450 CE, but its 20 confirmed eruptions include VEI 4 events.

**Novarupta (Katmai)** — Located in Katmai National Park on the Alaska Peninsula, [[volcano:novarupta|Novarupta]] produced the largest volcanic eruption of the 20th century on June 6–8, 1912 — a VEI 6 event that ejected 13 km³ of tephra and created the Valley of Ten Thousand Smokes. The eruption was so powerful that it was heard 1,200 km away in Juneau, and ash fell on Kodiak Island, 160 km away, in darkness for three days. Though initially attributed to nearby Mount Katmai, the eruption actually occurred at a new vent — Novarupta — at the base of Katmai's flank.

**Shishaldin** — The highest peak in the Aleutian Islands at 2,857 m (9,373 ft), Shishaldin is a strikingly symmetrical stratovolcano on Unimak Island with 40 confirmed eruptions. Its near-constant low-level steam emissions and frequent minor eruptions make it one of the most active volcanoes in North America. It erupted most recently in 2023 and has been compared to [[volcano:fujisan|Mount Fuji]] for its nearly perfect conical profile.

**Pavlof** — One of the most consistently active volcanoes in the Aleutian Arc, Pavlof is a 2,493 m (8,179 ft) stratovolcano on the Alaska Peninsula with 44 confirmed eruptions — the third-highest count for any U.S. volcano. Its eruptions frequently disrupt aviation with ash plumes reaching 8–12 km altitude. Pavlof last erupted in 2022.

**Mount Shasta** — A massive 4,317 m (14,163 ft) stratovolcano in northern California, Mount Shasta is the second-tallest volcano in the Cascades and has produced 22 confirmed eruptions, the most recent around 1250 CE. Its combination of large volume (~350 km³), active glacial system, and proximity to the city of Mount Shasta (~3,500 people) and Interstate 5 makes it a significant volcanic hazard.

**Cleveland** — Mount Cleveland, at 1,730 m (5,676 ft) on Chuginadak Island in the central Aleutians, is one of the most active volcanoes in North America. It produced 22 eruptions in the historical record and is frequently at elevated alert levels. Its remote location means eruptions primarily threaten aviation, but it is capable of explosive events up to VEI 3.

**Crater Lake (Mount Mazama)** — [[volcano:crater-lake|Crater Lake]] in southern Oregon is a 2,487 m (8,159 ft) caldera that formed during the cataclysmic VEI 7 eruption of Mount Mazama approximately 7,700 years ago — the only known VEI 7 event in the contiguous United States. The resulting caldera, 8 by 10 km across and 592 m deep, now holds the deepest lake in North America. Though the last eruption was around 2850 BCE, the volcanic system is not considered extinct.

**Augustine** — A 1,252 m (4,108 ft) lava dome complex in Cook Inlet, Alaska, Augustine has produced 22 confirmed eruptions including VEI 4 events. Its proximity to Anchorage (~280 km) and the critical Cook Inlet shipping lanes makes it one of the most hazardous Alaskan volcanoes. Its most recent eruption was in 2006.

**Redoubt** — With 97 confirmed eruptions — the second-highest count for any U.S. volcano — Redoubt is a 3,108 m (10,197 ft) stratovolcano on the western shore of Cook Inlet, Alaska. Its 1989–90 eruption famously caused a KLM Boeing 747 to lose all four engines after flying through an ash cloud at 7,600 m altitude; the plane descended 4,000 m before the engines were restarted. Redoubt's most recent eruption was in 2009.

The volcanic history of the United States spans tens of thousands of years and includes some of the most powerful eruptions in the Holocene record. The country's 165 volcanoes have collectively produced over 1,281 documented eruptions, including 61 events of VEI 4 or greater.

The most cataclysmic eruption in what is now the United States occurred approximately 7,700 years ago when Mount Mazama in southern Oregon collapsed in a VEI 7 eruption — the largest magnitude eruption in the Holocene record for North America north of Mexico. The explosion ejected roughly 50 km³ of material, sent ash across eight present-day states and three Canadian provinces, and created the caldera now filled by Crater Lake. Tephra from the Mazama eruption serves as a key chronological marker across the Pacific Northwest.

Alaska has dominated the U.S. eruption record in both frequency and intensity. The VEI 6 eruptions at Fisher Caldera (~7420 BCE), Aniakchak (~6300 BCE and ~1645 BCE), Black Peak (~1900 BCE), Veniaminof (~1750 BCE), and Okmok (~100 BCE) were among the largest explosive events in the Holocene. The VEI 6 eruption of Mount Churchill in the Wrangell Range around 847 CE produced the White River Ash, one of the most widely distributed tephra layers in North America, depositing recognizable ash over 540,000 km².

The eruption of [[volcano:novarupta|Novarupta]] in June 1912 stands as the largest volcanic event of the 20th century anywhere on Earth. The three-day VEI 6 eruption produced 13–15 km³ of tephra — thirty times more than the 1980 eruption of St. Helens — and created the Valley of Ten Thousand Smokes, a 40 km² pyroclastic flow deposit up to 200 m thick.

Remarkably, no one was killed, thanks to the extreme remoteness of the Katmai region.

The May 18, 1980 eruption of [[volcano:st-helens|Mount St. Helens]] remains the defining volcanic disaster of American history. A magnitude 5.1 earthquake triggered the collapse of the volcano's north face — the largest landslide ever recorded — which unroofed the pressurized magma system and produced a devastating lateral blast traveling at 480 km/h.

The eruption killed 57 people, destroyed 250 homes, flattened 600 km² of forest, and caused an estimated $1.1 billion in damage (1980 dollars). The eruption column reached 24 km altitude and deposited measurable ash across 11 states. The event fundamentally transformed volcanic monitoring and hazard assessment in the United States.

In Hawaii, [[volcano:kilauea|Kilauea]] has erupted almost continuously since 1983. The prolonged Puʻu ʻŌʻō eruption (1983–2018) was one of the longest-lived rift eruptions in historical records, producing roughly 4.4 km³ of lava over 35 years. The dramatic 2018 lower East Rift Zone event destroyed over 700 homes in the Puna District and added approximately 3.5 km² of new land to the island. [[volcano:mauna-loa|Mauna Loa's]] November 2022 eruption, after 38 years of dormancy, reminded observers that Earth's largest active volcano remains very much alive.

The volcanic hazards facing the United States are as diverse as its tectonic settings. In the Cascades, explosive stratovolcanoes like [[volcano:rainier|Rainier]], St. Helens, and Glacier Peak pose threats from pyroclastic flows, lahars, tephra fall, and lateral blasts.

Mount Rainier is considered the most dangerous volcano in the Cascades — and potentially the entire country — because its extensive glacial ice cap would generate massive lahars in the event of a major eruption. USGS modeling indicates lahars could reach the densely populated Puyallup and White River valleys, home to approximately 100,000 people, within 30 to 60 minutes.

Ash-fall hazards from Cascade eruptions could affect millions. The 1980 St. Helens eruption deposited significant ash across eastern Washington and beyond, disrupting transportation, agriculture, and aviation.

A comparable eruption today would ground air traffic throughout the Pacific Northwest and potentially blanket cities like Portland and Seattle with centimeters of abrasive volcanic ash.

In Alaska, the primary hazard is to aviation. The North Pacific air corridor carries approximately 50,000 passengers per day on routes between North America and Asia, and many of these flight paths pass directly over or near Aleutian volcanoes. Volcanic ash clouds can damage jet engines, abrade windshields, and clog pitot tubes — as dramatically demonstrated during the 1989 Redoubt eruption when a KLM 747 temporarily lost all four engines.

The Alaska Volcano Observatory issues aviation color codes and coordinates closely with the Volcanic Ash Advisory Centers.

In Hawaii, lava flows are the primary hazard. Kilauea's 2018 eruption destroyed 716 structures and displaced thousands of residents in the Puna District. [[volcano:mauna-loa|Mauna Loa]] lava flows could potentially reach the city of Hilo (population ~45,000) in as little as three hours from some vents. Volcanic gas emissions, particularly sulfur dioxide (SO₂), create persistent volcanic smog (vog) that affects air quality across the Hawaiian Islands.

The USGS Volcano Hazards Program operates a national volcanic threat assessment that ranks 161 U.S. volcanoes by combined hazard and exposure. The top five threats, in order, are: Kilauea, [[volcano:st-helens|Mount St. Helens]], [[volcano:rainier|Mount Rainier]], Redoubt, and Mount Shasta.

U.S. volcanoes are concentrated in five major geographic regions, each with distinct tectonic origins and eruption characteristics.

The **Aleutian Arc** stretches approximately 2,500 km from Buldir Island in the west to the Alaska Peninsula in the east. This is the most volcanically dense region in the United States, containing 46 stratovolcanoes on the Aleutian Ridge and 27 additional volcanoes along the Alaska Peninsula. The entire arc results from the northwestward subduction of the Pacific Plate beneath the North American Plate at the Aleutian Trench.

Most Aleutian volcanoes are uninhabited, but their eruptions pose severe aviation hazards.

The **Cascade Range** extends approximately 1,100 km from Lassen Peak in northern California to Mount Baker near the Canadian border. Its 19 major volcanic centers are spaced at roughly 50–70 km intervals along the High Cascades, fueled by the subduction of the Juan de Fuca and Gorda microplates. The Cascades include several of the most hazardous volcanoes in the nation due to their proximity to Pacific Northwest population centers.

The **Hawaiian Islands** contain 6 Holocene volcanic centers atop the Pacific Plate, above the Hawaiian hotspot. Volcanic activity is concentrated on the Big Island, where Kilauea and Mauna Loa remain active, and on the submarine Kamaʻehuakanaloa. Haleakalā on Maui last erupted around 1750 CE.

The **Basin and Range/Yellowstone** province spans the western interior, where extensional tectonics and the Yellowstone hotspot have generated scattered volcanic fields across Idaho, Oregon, Nevada, Utah, Arizona, Colorado, and New Mexico. Though eruption frequency is low, the Yellowstone caldera system — while not in the Smithsonian Holocene database (last eruption ~70,000 years ago) — represents a supervolcanic hazard of global significance.

The **Mariana Arc** in the western Pacific adds 25 volcanic centers to the U.S. inventory, most of them submarine. These volcanoes form along the Mariana Trench where the Pacific Plate subducts beneath the Philippine Sea Plate.

Volcanism has profoundly shaped American culture, economy, and national identity. In Hawaii, volcanoes are central to Native Hawaiian culture and spirituality — Kīlauea is regarded as the home of Pele, the goddess of fire, and volcanic landscapes are sacred sites (wahi pana) throughout the islands. Hawaii Volcanoes National Park, established in 1916, draws over 1.3 million visitors annually and is a UNESCO World Heritage Site.

The geothermal energy generated by volcanic heat provides roughly 25% of the Big Island's electricity.

In the Pacific Northwest, the 1980 eruption of Mount St. Helens transformed public awareness of volcanic hazards and led to the establishment of the Mount St. Helens National Volcanic Monument, which draws over 500,000 visitors per year.

The eruption catalyzed a revolution in volcanic monitoring — the USGS Volcano Hazards Program expanded dramatically in its aftermath, and the Cascades Volcano Observatory was established at Vancouver, Washington, in 1982.

Mount Rainier and Crater Lake are among the most visited volcanic landscapes in the National Park system. Crater Lake National Park receives approximately 700,000 visitors annually, while Mount Rainier National Park draws over 2 million. Alaska's Katmai National Park, site of the 1912 Novarupta eruption and the Valley of Ten Thousand Smokes, combines volcanic tourism with world-famous bear viewing.

Volcanic soils support agriculture across Hawaii (coffee, macadamia nuts), the Pacific Northwest (viticulture in Oregon and Washington), and the Willamette Valley. In the American Southwest, volcanic landscapes including Sunset Crater, Capulin Volcano, and Craters of the Moon are protected as National Monuments, preserving both geological heritage and the cultural histories of Indigenous peoples who witnessed and recorded eruptions.

The United States offers some of the most accessible volcanic tourism in the world. Hawaii Volcanoes National Park on the Big Island provides the easiest opportunity to witness active volcanism — when Kilauea is erupting, visitors can often observe lava activity from designated viewpoints within the park. The park's Crater Rim Drive, Thurston Lava Tube, and Devastation Trail are open year-round.

Check the [[ext:https://www.usgs.gov/volcanoes/kilauea|USGS Kilauea page]] for current eruption status before visiting.

Mount St. Helens National Volcanic Monument in Washington offers the Johnston Ridge Observatory, which sits just 8 km from the crater and provides sweeping views of the 1980 blast zone and the growing lava dome. The monument is typically open from May through October.

Climbers can summit St. Helens with a permit (available through recreation.gov).

Crater Lake National Park in Oregon showcases the stunning caldera formed by the VEI 7 Mount Mazama eruption. Rim Drive (53 km) circles the lake, and boat tours reach Wizard Island within the caldera. The park is accessible from late June through October due to heavy snowfall.

In Alaska, Katmai National Park offers flightseeing tours over the Valley of Ten Thousand Smokes and access to the volcanic landscape surrounding Novarupta. Denali flightseeing tours provide views of Mount Wrangell. The Aleutian Islands are extremely remote and generally not accessible to casual tourists.

Other notable volcanic destinations include Lassen Volcanic National Park (California), Sunset Crater Volcano National Monument (Arizona), Craters of the Moon National Monument (Idaho), and Haleakalā National Park (Maui). The Yellowstone caldera and its associated geothermal features — including Old Faithful, Grand Prismatic Spring, and the Norris Geyser Basin — attract over 4 million visitors annually.