Home

Rising gradually to more than 4 km (13,100 ft) above sea level, Mauna Loa is the largest active volcano on our planet.


Summary

Its long submarine flanks descend to the sea floor an additional 5 km (16,400 ft), and the sea floor in turn is depressed by Mauna Loa's great mass another 8 km (26,200 ft). This makes the volcano's summit about 17 km (55,700 ft) above its base! The enormous volcano covers half of the Island of Hawai‘i and by itself amounts to about 85 percent of the area of all the other Hawaiian Islands combined.

The Hawaiian name "Mauna Loa" means "Long Mountain." This name is apt, for the subaerial part of Mauna Loa extends for about 120 km (74 mi) from the southern tip of the island to the summit caldera and then east-northeast to the coastline near Hilo.

Mauna Loa is among Earth's most active volcanoes, having erupted 33 times since its first well-documented historical eruption in 1843. It has produced large, voluminous flows of basalt that have reached the ocean eight times since 1868. It last erupted in 1984, when a lava flow came within 7.2 km (4.5 mi) of Hilo, the largest population center on the island. Mauna Loa is certain to erupt again, and with such a propensity to produce large flows, we carefully monitor the volcano for signs of unrest.

Read our Frequently Asked Questions about Mauna Loa.

News

Date published: November 8, 2021

Newly Revised "Geologic map of the State of Hawaii" publication available

The USGS recently published a revised “Geologic Map of the State of Hawaii.” This map—originally published in 2007—has been updated to include more recent geologic deposits, including lava flows from Kīlauea’s Pu‘u‘ō‘ō vent on the middle East Rift Zone from 2007–2018 and lava flows erupted during Kīlauea’s 2018 lower East Rift Zone eruption.

Date published: August 19, 2021

Photo and Video Chronology – Mauna Loa – August 19, 2021

HVO scientists collect high-precision Global Positioning System (GPS) data to assess hazards and understand evolving processes at Mauna Loa.

Date published: July 15, 2021

Volcano Watch — Learning from the 1984 eruption of Mauna Loa

The most recent page in Mauna Loa’s eruptive history was written in 1984. The eruption began in March of 1984, about a decade after the 1975 summit eruption (the topic of last week’s “Volcano Watch” article). Here’s a quick look at how the eruption proceeded and its impacts on residents ...

Find a U.S. Volcano