Mauna Loa backs off eruption-alert tease
By Christie Wilson
Advertiser Neighbor Island Editor
Make no mistake — Mauna Loa is going to erupt.
Advertiser library photo • 1984
But it probably won't happen as soon as many people feared after scientists last year detected that the caldera atop the 13,680-foot mountain was inflating after eight years of shrinking, indicating a swelling of the magma reservoir two miles beneath the summit.
It's been nearly 19 years since the last Mauna Loa eruption. That's the volcano's second longest period of quiet in recorded history.
The pattern of swelling was similar to that observed before the past two eruptions, but at an even greater rate. That trend continued until a few weeks ago, when the rate of inflation significantly slowed, lessening the likelihood of an eruption.
"Everyone knows Mauna Loa will erupt again. It's been a long time since the last eruption," said geophysicist Peter Cervelli of the Hawaiian Volcano Observatory. "But it looks like the recent unrest may be winding down. ... Our best guess is that it's going to roll over and return to normal.
"But the volcano has a way of laughing at our best guesses."
When swelling of the Mauna Loa caldera, known as Moku'aweoweo, began in late April or May and continued unabated through the end of the year, volcano scientists and civil defense officials held a series of community meetings to inform the public about the latest scientific readings and to discuss possible evacuation plans in case lava spilled down the steep mountainside.
It has been nearly 19 years since the last Mauna Loa eruption in March 1984, which lasted 22 days. That's the second longest period of quiet in recorded history.
The longest period without an eruption lasted 25 years, between 1950 and 1975.
• For daily updates on the Kilauea and Mauna Loa volcanoes and other information, check the Hawaiian Volcano Observatory Web site.
Cervelli said the threat of a Mauna Loa eruption was "overblown" in some Mainland news media accounts, perhaps causing unnecessary alarm.
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Many people don't understand that Mauna Loa is not an explosive volcano, he said, and that in the 33 eruptions since 1843 when written records start, there has not been a single death.
In addition, seven of the 15 eruptions over the past century were confined to the summit caldera, making them "largely a scientific curiosity," he said.
With Mauna Loa apparently quieting down, Cervelli said "we're going to get down to business and try to explain what happened and improve our understanding" of the volcano.
Because of limited measuring techniques, scientists were at a disadvantage when trying to put new data into a historical context. Only recently have Hawaiian Volcano Observatory researchers been able to use instruments that can provide near-real-time measurements with unprecedented precision.
Since 1999, a series of geographic positioning system receivers have been installed on the summit and upper flanks of Mauna Loa to detect changes in shape of the volcano. The system gathers data using a network of 24 satellites orbiting the Earth. Scientists also use electronic tiltmeters that detect minute changes in a volcano's shape.
Cervelli predicted that volcano monitoring will undergo a technology-driven revolution over the next 50 years "as big as the one that occurred 50 to 70 years ago with seismology instrumentation."
Yet despite the best science available today, "you can never tell," Cervelli said. "Volcanoes are capable of throwing curve balls at you."
Contact Christie Wilson at cwilson@honoluluadvertiser.com or (808) 244-4880.
