Mauna Loa

This light gray block of rock (backpack for scale) is part of the approximately 830-year-old explosion deposit on the northwest rim of Moku‘āweoweo, the summit caldera of Mauna Loa. USGS photo by F.A. Trusdell.

Mauna Loa, Earth's largest active volcano, has erupted 33 times since 1843, producing the lava flows shown in black. All of these historic eruptions started at the summit of the volcano. From there, the eruptions either stayed in the summit area or migrated down the volcano's Northeast or Southwest Rift Zones. Some Mauna Loa eruptions occurred at radial vents, indicated by

Mauna Loa tends to erupt large, fast-moving lava flows. About 36 hours after the 1984 eruption began on March 25, lava flowed downstream (toward bottom-right of photo) through this ‘A‘ā channel down rift from the main vent. For scale, note the USGS scientists at work on the left side of the 70-m- (77-yard-) wide lava channel.

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Aerial view of a bomb detonating on Mauna Loa near the 8500-foot elevation source of the 1935 lava flow on the morning of December 27, 1935. This was one of twenty 600-pound bombs dropped on the lava flow that morning by the Army Bombing Squadron from Luke Field, O‘ahu. Photo by Army Air Corps, 11th Photo Section.

Close up of Sheet 2 of "Lava inundation zone maps for Mauna Loa, Island of Hawai‘i," recently published by the U.S. Geological Survey. Colors depict lava Inundation zones for the Kaumana, Waiākea, and Volcano-Mountain View regions on Mauna Loa. Yellow indicates the volcano's Northeast Rift Zone, one area along which lava could erupt. The extent of the 1984 eruption and

Aerial view of Mauna Loa erupting on the morning of March 25, 1984, the first day of the volcano's most recent eruption. The lava flow was advancing southeast, toward Kīlauea, from fissure vents at an elevation of about 11,200 feet on Mauna Loa's Northeast Rift Zone. Moku‘āweoweo, Mauna Loa's summit caldera, is visible at top left. USGS photo by J.P. Lockwood.

A USGS Hawaiian Volcano Observatory geologist monitored the advance of an ‘A‘ā lava flow on April 6 during the 1984 Mauna Loa eruption. This flow was about 4 m (13 ft) high and advancing at a rate of 50 m (55 yards) per hour. Lava reached within 6 km (4 mi) of Hilo city limits before the 22-day-long eruption ended on April 15. USGS photo by P.W. Lipman.

USGS Hawaiian Volcano Observatory field engineers begin the process of lowering a tiltmeter into a deep borehole on the west flank of Mauna Loa. The installation is guided by a custom-built apparatus that includes a 3-D printed jig. This tiltmeter will help monitor the currently elevated activity of Mauna Loa Volcano. USGS photo.

A beautiful sunset over Mauna Loa (in distance at left) provided a backdrop to the lava lake within Halema‘uma‘u. HVO and Jaggar Museum are on the horizon near the center of the panorama.