Frank Trusdell

Frank A. Trusdell

Geologist at U.S. Geological Survey

12201 Sunrise Valley Drive, Reston, Virginia, United States
HQ Phone:
(703) 648-4000

General Information


masters  - 


Scientist Participant  - Hawaiian Volcano Observatory&rsquo

Recent News  

Compiled by Frank Trusdell of the Hawaiian Volcano Observatory, this map is the electronic equivalent of a printed map that first appeared in 1996.

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"The alert level change at Mauna Loa reminds us that it is an active volcano that will erupt again someday, so we should be prepared," said Frank Trusdell, an HVO geologist who has extensively studied and mapped Mauna Loa.

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"When the Puu Oo eruption stops on the east rift zone of Kilauea," said Frank A. Trusdell, of the U.S. Geological Survey, who has studied Mauna Loa for the past two decades.
Historically, eruptive periods at Kilauea and Mauna Loa volcanoes appear to be inversely correlated. In the past, when Mauna Loa was exceptionally active, Kilauea was in sustained lava lake activity, he said. "If the flanks become stable and buttress Mauna Loa's flank, then Mauna Loa erupts, but if there is an eruption along the rift zones of Kilauea and that mobilizes, in turn, the south flank, the (Kilauea) side of the volcano can't buttress Mauna Loa, so, Mauna Loa's flank keeps moving," Trusdell explained. "It keeps creating more and more space, so, the magma supply has to fill up all that excess space and it reduces the pressure." Currently, Mauna Loa's flank is moving toward Kilauea, reducing pressure on Mauna Loa thus lessening the likelihood of an eruption there, he said. Nevertheless, while Mauna Loa may not appear as though it's ready to erupt today, Trusdell stressed the importance of being prepared because time can be limited depending on where you live. According to data presented by Trusdell, scientists estimate, depending on the location of the actual eruption on Mauna Loa, it would take the lava about 29 hours to reach the shoreline below the Hawaiian Ocean View Estates subdivision of Ka'u, as little as three hours to reach the South Kona shoreline, eight days to reach Kiholo Bay and some 280 days to reach Hilo Bay. The USGS suggests all people who live on or near Mauna Loa learn about and keep up to date on the volcano's hazards and develop a family emergency plan in the event of an eruption. "Mauna Loa puts out lots of lava and has a steep slope, and, if you don't heed the warning you're going to end up in trouble," Trusdell said. Mauna Loa is the world's largest active volcano, said Trusdell, noting it extends 13,697 feet above sea level and about 3,100 feet below sea level. Its name meaning "long mountain" in Hawaiian. Mauna Loa covers more than 50 percent of Hawaii Island, extending into Hilo, most of the southern portion of the island and toward Kiholo Bay in North Kona. It's also 500 times greater in volume than Mt. Rainier, the picturesque volcano in Washington state. "Mauna Loa is so huge that it actually causes the Pacific plate it is residing on to sag under the weight of the volcano," said Trusdell, noting that like Kilauea, Mauna Loa remains in the shield stage, featuring a caldera at the summit some 3.7-by-1.9 miles - much larger than Kilauea's 1.2-by-1.9 miles. The volcano also has the capability to pump out a lot more lava than Kilauea, Trusdell said. Kilauea erupts 0.2 to 0.5 million cubic meters each day while Mauna Loa puts out 12 million cubic meters per day. "What Kilauea puts out in one day, in Mauna Loa's last eruption in 1984, Mauna Loa erupted in 20 minutes," Trusdell said. In all, Mauna Loa has erupted 33 times since 1843, which is when written records of volcanic eruptions began post European contact, Trusdell said. "For Mauna Loa, the trump card for volcanic hazards are the radial vents," Trusdell said. "If you live on a flank and a radial vent pops up in your backyard, then, well, your response times are very abbreviated." While only 170 years of written history exists for Mauna Loa, Trusdell said geologists have studied data and used radiocarbon dating to determine how many times Mauna Loa has erupted during the past 30,000 years. About 35 percent of all the lava on Mauna Loa has been dated, said Trusdell. He said 500 lava flows have been mapped and 300 flows radiocarbon dated. Over the past 3,000 years, Trusdell said, Mauna Loa erupted once every six years and evidence of four explosive events have been found. Since written records began, the volcano has erupted about once every five years, he said. "What the volcano did in the past is your best guide to what it will do in the future," Trusdell said, noting that the data is compiled into maps used by emergency officials, as well as residents and planners, to determine the threat level. The USGS monitors Mauna Loa using numerous seismic, GPS and tilt stations positioned on its flanks. When unrest is detected, usually a swarm of earthquakes greater than magnitude 1.8, scientists notify emergency officials and increase monitoring efforts. "When we start issuing these notices, you should get your things in order," Trusdell told attendees.

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