Mauna Loa — The Biggest Active Volcano on Earth (Hawaii History + 2026 Status)

**Mauna Loa is the largest active volcano on Earth.** Not the tallest — Mauna Kea next door beats it by about 100 feet — but by sheer volume of rock, Mauna Loa is unmatched. It's 60 miles long, 30 miles wide, covers half the Big Island, and rises 13,679 ft above sea level. If you measured from its base on the seafloor, Mauna Loa would be **56,000 feet tall** — taller than Mount Everest by 30%. ## The eruption history at a glance Mauna Loa has erupted **33 times since 1843**. The pattern is unusual — long stretches of dormancy followed by short, big eruptions: | Year | Duration | Significance | |---|---|---| | 1881 | Long | Lava flow reached the outskirts of Hilo | | 1899 | Short | Summit only | | 1907-1914 | Multiple flows | Westward toward Hualālai | | 1916, 1919, 1926, 1933, 1935, 1940, 1942 | Multiple short eruptions | Heavy 20th century pace | | **1950** | 23 days | Largest in modern record. 13.2 mi flow reached the ocean. | | 1975 | 1 day | Summit only | | **1984** | 21 days | Lava came within 4 miles of Hilo. National news. | | ⚠️ **2022** | **13 days** | First eruption in 38 years. Flows came within 1.7 miles of Saddle Road. | The **2022 eruption** was a big deal — first time Mauna Loa erupted since 1984, when most current Big Island residents weren't yet born. ## What the 2022 eruption was like **Started:** November 27, 2022 (around 11:30pm local) **Ended:** December 13, 2022 **Total duration:** 13 days **Lava extent:** Northeast flank flows, came within 1.7 miles of Saddle Road (the main road between Hilo and Kona). What it looked like: - Glowing orange lava fountains visible at the summit from 30+ miles away - Lava flows traveled at ~100 ft per hour - Estimated 200 million cubic yards of lava erupted - Saddle Road came within hours of being cut off — would have severed direct Hilo↔Kona drive - **No homes were lost.** No injuries. The eruption ended naturally — the lava supply at the summit ran low, fissures sealed. ## Where Mauna Loa stands today (2026) Mauna Loa is currently classified as **Yellow Advisory** by the Hawaiian Volcano Observatory. That means: - Elevated unrest (more seismic activity than baseline) - Not currently erupting - Could erupt with relatively short warning (hours to weeks) **For comparison**, Mauna Loa's neighbor Kīlauea is also currently active (intermittent summit eruptions). Two simultaneous eruptions on the same island is rare but possible. ## Visiting Mauna Loa Several ways: ### 1. Hawaiʻi Volcanoes National Park summit area The Mauna Loa Road branches off Highway 11 inside the National Park. **The road climbs to ~6,700 ft** and ends at a lookout. Walk-up access. No fee beyond park entry ($30). ### 2. Mauna Loa Summit Trail Hardcore hike. **19 miles round trip, 7,000 ft elevation gain.** 2-3 days, requires permits, very technical. Don't attempt without research + altitude acclimatization. ### 3. Mauna Loa Observatory (research station) On the north side. Famous for its atmospheric CO₂ measurements (the Keeling Curve started here). **Not open to the public** but the road up provides spectacular views. ### 4. Saddle Road drives Highway 200 between Hilo and Kona crosses the saddle between Mauna Loa and Mauna Kea. The southern view from the saddle is Mauna Loa's huge sloping shield. Most underrated drive on the Big Island. ## Mauna Loa vs Mauna Kea (the eternal Hawaii rivalry) - **Mauna Loa** = active, larger volume, more recent eruptions, less developed for tourists - **Mauna Kea** = dormant, slightly taller, famous astronomy observatories, drivable summit They're sibling mountains. If you have one day on the Big Island, the Mauna Kea summit drive + stargazing is the more accessible experience. **If you have two days, do both.** ## What locals do during an eruption The 2022 eruption brought out 6 nights in a row of locals driving to the Saddle Road area to watch the glow from the eruption fountains. Coolers, lawn chairs, lots of "remember 1984?" stories. If you're in Hawaii during an eruption, **don't drive directly toward the eruption** unless cleared by emergency management. Watch from designated safe viewing spots (Volcanoes National Park, official lookouts). ## More Big Island reading - [Big Island Things to Do 2026 →](/blog/big-island-things-to-do-2026) - [Vog in Hawaii — Forecast Guide →](/blog/what-is-vog-hawaii-forecast) - [Best Snorkeling Spots in Hawaii →](/blog/best-snorkeling-spots-hawaii-2026) - [Browse all Big Island events →](/island/big-island)