🌋VolcanoAtlas

Mauna Loa

The Largest Active Volcano on Earth

Elevation

4,170 m

Last Eruption

2022

Type

Shield volcano

Country

United States

Location

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Volcanic Hazards & Risk Assessment

Primary Hazards

  • Lava flows and fountaining
  • Volcanic gas emissions
  • Local explosive activity

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 Activity4 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

Related Volcanoes

All United States Volcanoes
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Hawaiʻi (Big Island)
Regional volcanoes
a dark sky with red clouds in it

Daniel Norris

via Unsplash

silhouette of mountain under blue sky

Raph Howald

via Unsplash

a volcano erupting at sunset

Sherry Jiang

via Unsplash

a person looking at a large fire

Sherry Jiang

via Unsplash

A man is running on top of a mountain

Mick Haupt

via Unsplash

A lone tree in a grassy field under a blue sky

Dave Meckler

via Unsplash

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Interesting Facts

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Mauna Loa's total volume of approximately 74,000 km³ makes it roughly 100 times larger than Mount St. Helens and the single most massive mountain on Earth.

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Measured from its base on the ocean floor (~5,000 m below sea level), Mauna Loa rises approximately 9,170 m — making it taller than Mount Everest measured base-to-peak.

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The weight of Mauna Loa has depressed the underlying oceanic crust by approximately 8 km, meaning the volcano's true structural height from depressed base to summit exceeds 17 km.

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Almost 90% of Mauna Loa's surface is covered by lava flows less than 4,000 years old — the volcano literally rebuilds its own surface faster than most geological processes can erode it.

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During the 1950 eruption, lava from the Southwest Rift Zone reached the ocean — a distance of 24 km — in just 3 hours, averaging roughly 8 km/h.

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In 1935, the U.S. Army Air Corps dropped 20 demolition bombs on Mauna Loa's lava tubes in the first-ever attempt to divert a volcanic eruption by aerial bombardment — proposed by HVO founder Thomas Jaggar.

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The Mauna Loa Observatory, at 3,397 m on the northern flank, has produced the Keeling Curve — the continuous atmospheric CO₂ record since 1958 that is considered the most important dataset in climate science.

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Mauna Loa's 2022 eruption attracted global media attention as the world's largest active volcano reawakened after 38 years of dormancy — the longest quiet interval in its recorded history.

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The volcano has erupted 33 times since 1843, averaging roughly one eruption every 5–6 years, making it one of the most frequently active volcanoes in the world.

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Mokuʻāweoweo, the summit caldera, is approximately 6 × 2.5 km — large enough to contain the entire city center of a mid-sized city.

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Mauna Loa and neighboring Kīlauea together account for more than half of all historically documented eruptions in the United States.

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Two massive debris avalanches from Mauna Loa's flanks traveled nearly 100 km across the ocean floor — the Alika 2 slide (~105,000 years ago) likely generated a massive tsunami across the Pacific.

Frequently Asked Questions

Is Mauna Loa the biggest volcano in the world?
Mauna Loa is the largest active volcano on Earth by volume (~74,000 km³) and surface area (~5,271 km²). However, Tamu Massif, an extinct underwater volcano in the Pacific Ocean, is larger by area (approximately 310,000 km²), though its volcanic origin is debated. Among the solar system's volcanoes, Olympus Mons on Mars dwarfs all Earth volcanoes. On Earth, Mauna Loa holds the undisputed title of largest currently active volcano. Its mass is so enormous that it has depressed the underlying oceanic crust by approximately 8 km — giving it a true structural height exceeding 17 km from depressed base to summit.
When did Mauna Loa last erupt?
Mauna Loa's most recent eruption occurred from November 27 to December 13, 2022, lasting approximately 16 days. The eruption began in the Mokuʻāweoweo summit caldera and quickly migrated to the Northeast Rift Zone, producing lava flows that advanced toward Saddle Road — the main highway connecting Hilo and Kona. Lava came within approximately 2.8 km of the road before the eruption ended. This was the volcano's first eruption since 1984, ending a 38-year repose that was the longest in its recorded history. No casualties or structural damage occurred.
Is Mauna Loa dangerous?
Yes. While Mauna Loa eruptions are typically non-explosive (VEI 0), the primary hazard — fast-moving basaltic lava flows — poses a significant threat to the approximately 200,000 people living on the Island of Hawaiʻi. Lava flows from the Northeast Rift Zone can reach Hilo (population ~45,000) within days, and Southwest Rift flows reached the coast in just 3 hours during the 1950 eruption. Additional hazards include volcanic fog (vog), lava entry into the ocean producing toxic laze, seismic activity, and the remote possibility of catastrophic flank collapse generating Pacific-wide tsunamis. The USGS ranks Mauna Loa among the highest-threat volcanoes in the United States.
How tall is Mauna Loa?
Mauna Loa's summit stands at 4,170 m (13,681 ft) above sea level. However, this dramatically understates the volcano's true size. Measured from its base on the ocean floor (approximately 5,000 m below sea level), the mountain rises approximately 9,170 m (30,085 ft) — exceeding Mount Everest's 8,849 m above sea level. Furthermore, the weight of the volcano has depressed the underlying oceanic crust by roughly 8 km, meaning the full structural height from the depressed base to the summit exceeds 17,000 m. Despite being slightly shorter above sea level than neighboring Mauna Kea (4,207 m), Mauna Loa is vastly larger in total volume.
What type of volcano is Mauna Loa?
Mauna Loa is a shield volcano — the largest type of volcano on Earth, built from thousands of overlapping layers of fluid basaltic lava flows. Shield volcanoes have gently sloping flanks (typically 4–8°), in contrast to the steep-sided profile of stratovolcanoes like Mount Fuji or Vesuvius. Mauna Loa's basaltic magma is low in silica and dissolved gases, which allows it to flow freely rather than building up explosive pressure. The name 'shield volcano' comes from the resemblance to a warrior's shield laid flat on the ground. Mauna Loa is the textbook example of this volcano type.
How does Mauna Loa compare to Kīlauea?
Mauna Loa and Kīlauea are neighboring shield volcanoes fed by the same Hawaiian hotspot, but they differ significantly. Mauna Loa is approximately four times larger by volume (~74,000 km³ vs ~19,000 km³), three times taller above sea level (4,170 m vs 1,247 m), and has more recorded eruptions (111 vs 77). However, Kīlauea has been more continuously active in recent decades — its 1983–2018 East Rift Zone eruption lasted 35 years, and it has erupted several times since. Mauna Loa tends to erupt less frequently but produces larger individual lava flows. Both are monitored by the Hawaiian Volcano Observatory, and both pose significant hazards to Big Island communities.
Can you visit Mauna Loa?
Yes, Mauna Loa is within Hawaiʻi Volcanoes National Park (entry fee: $30 per vehicle). The primary hiking route, the Mauna Loa Trail, is a 31-km (19-mi) trek from the Mauna Loa Lookout (2,030 m) to the summit caldera, typically completed over 3–4 days with stays at two backcountry cabins (free permit required). The hike is strenuous, crossing barren lava flows at high altitude with no water sources and exposure to extreme weather. A shorter approach via the Mauna Loa Observatory Road reaches 3,397 m by vehicle. For less demanding visits, the Kīpukapuaulu (Bird Park) trail offers an accessible walk through native forest on Mauna Loa's flank.
What is the Keeling Curve and what does it have to do with Mauna Loa?
The Keeling Curve is the continuous record of atmospheric carbon dioxide concentration measured at the Mauna Loa Observatory since 1958, created by scientist Charles David Keeling. The observatory sits at 3,397 m on Mauna Loa's northern flank — chosen because its high altitude, remote mid-Pacific location, and distance from major pollution sources make it ideal for measuring background atmospheric composition. The curve has documented the rise of CO₂ from 315 parts per million in 1958 to over 425 ppm in 2024, providing the most important direct evidence of human-caused increases in greenhouse gases. It is arguably the most significant scientific dataset produced by any volcanic site.