U.S. Geological Survey - Hawaiian Volcano Observatory

Mauna Loa - Current Activity - History

Volcanic Hazards

"It is profoundly significant that the Hawaiians of Ka`u did not fear or cringe before, or hate, the power and destructive violence of Mauna Loa. They took unto them this huge mountain as their mother, and measured their personal dignity and powers in terms of its majesty and drama."

Pukui and Handy, 1952

Historical Eruptions Spotlight
Potential Lava-Flow Inundation Areas

Since 1984, more than $2.3 billion have been invested in new construction on the slopes of Mauna Loa, and the amount increases daily. But it is well to remember that Mauna Loa will certainly erupt again, most likely within a few years to a few decades. Areas covered by the volcano's historical lava flows are clear reminders of the general pathways that the next lava may travel--that is, down nearly any side of the volcano depending on the where the next eruption occurs.

• Summary of lava-flow hazards from Mauna Loa
• Overview of volcanic hazards on Hawai`i

The Next Eruption: Where Will the Lava Flow?

Based on Mauna Loa's historical eruptions and detailed geologic maps of the volcano's surface, we have identified relative lava-flow hazard zones on the volcano and throughout the island of Hawai`i. Six zones were recognized on Mauna Loa. Until the next eruption begins, however, we cannot determine with certainty which areas will be inundated by lava during the next eruption.

Fissure eruption and lava flows on the upper northeast rift zone of Mauna Loa about 10 hours after the start of the 1984 eruption. The eruption began from vents in the summit caldera (top) and then migrated about 10 km down the rift zone to the fissure shown here.

The high rate of eruption typical of Mauna Loa, combined with the volcano's steep slopes, means that flows can move far and fast. Hence our monitoring efforts to identify areas threatened by lava in the first few hours of the next eruption assume great importance.

Lava-Flow Directions Depend on Four Key Factors

• location of the erupting vent(s)
• rate of lava production
• duration of the eruption (see history table)
• local topography, especially steepness of ground

As shown by the1984 eruption that sent lava flows toward Hilo, scientists must monitor these factors constantly during an eruption to provide specific warnings about areas likely to be inundated and to identify areas immediately threatened by moving lava.

Summary of historical eruptions

References:

Trusdell, F., A., 1995, Lava flow hazards and risk assessment on Mauna Loa Volcano, Hawai`i, in Rhodes, J.M., and Lockwood, J. P. (eds.), Mauna Loa revealed: structure, composition, history, and hazards: Washington D.C., American Geophysical Union Monograph 92, p. 327-336.

Pukui, K., and Handy J., 1952, The Polynesian family system in Ka`u, Hawai`i, Bishop Museum Press, Honolulu, 300 p.