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Remembering Mauna Loa volcano's last eruption: 30 years ago this week

Mauna Loa lava channel on March 28, 1984. Photo: USGS

This Tuesday marks the 30th anniversary of the last eruption of the Big Island's Mauna Loa volcano.

At 1:30 a.m. on March 25, 1984, the largest active volcano on Earth woke up suddenly and spectacularly after nine years of slumber. The eruption sent several fast-moving fingers of lava down Mauna Loa’s gentle slopes, primarily over old flows and through upslope forests. One of the fastest of these fingers of molten earth quickly took direct aim at Hilo, the Big Island’s largest city, putting its residents on high alert in the days that followed.

Mauna Loa curtain of fire, one hour after the start of the eruption, March 25, 1984. Photo: USGS

The eruption ended three weeks after it began, its longest finger of lava stopping just four miles from the nearest Hilo home. Mauna Loa has been quiet ever since.

Prior to its recent three decade eruptive dry spell, Mauna Loa had erupted 33 times since 1843—an average rate of one eruption every five years. Going further back into research on the 13,680-foot volcano’s eruptive history, scientists at the Hawaii Volcano Observatory say Mauna Loa has erupted about once every six years for the last 3,000 years.

Mauna Loa lava flow at night, as seen from Hilo. Photo: David Little/USGS

So why hasn’t Mauna Loa erupted in the last three decades? (See next page.)

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Check out these related posts:
Remembering Mauna Loa's last eruption
Mauna Lani among Earth's most Earth-friendly resorts
The woes of Mauna Kea

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