1975 Eruption of Mauna Loa

Aerial nighttime view of a molten lava flow cascading into a crater
Lava cascades into Lua Hou on July 6th, 1975 (USGS/RT Holcomb)
Though the 1975 eruption lasted less than a day, it produced spectacular effusive lava flows that moved down the volcano's northeast flank.

Just before midnight on July 5th, 1975, Mauna Loa ended its quarter-century period of quiesence. At the time, it was the volcano's longest recorded period without eruptive activity... soon to be outdone by the period following the 1984 eruption.

At 11:42 p.m., a small glow was noted above the southwest end of Moku‘āweoweo. Within one minute, the glow extended across the entire summit area and a fume cloud more than 3,300 ft (1,000 m) high was illuminated with a bright orange-red glow from the lava fountains on the caldera floor. Lava flowed across the caldera, and into the upper parts of the Southwest and Northeast Rift Zones, the latter of which became the epicenter of activity. However, the eruption would be brief, concluding at 7:30 p.m. the next day.
 
Molten lava flows on a mountainside with a silhouetted mountain beyond at sunrise
The sun rises beyond Mauna Kea as lava flows down the side of Mauna Loa on the morning of July 6th, 1975 (USGS Photo/D. Peterson)
 
Aerial view of a volcanic fissure spewing lava with a large volcanic caldera in the background
The summit of Mauna Loa on July 6th, 1975, with Moku‘āweoweo caldera visible in the background (USGS Photo)
 
Aerial view of erupting lava vents with plumes of gas
Fountains up to 65 feet (20 m) high erupt from fissures on the northeast flank of Mauna Loa early Sunday morning, July 6, 1975. (USGS Photo)
 
 
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Last updated: February 10, 2021

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