Today marks the 25th anniversary of the ongoing eruption of Kilauea volcano that so far has destroyed 190 structures in Puna, including Kalapana Village, buried almost nine miles of highway and shown no sign of slowing or stopping.

Scientists with the U.S. Geological Survey's Hawaiian Volcano Observatory say the eruption is the longest in Kilauea's rift zone in at least the past 800 years, and may be the largest Kilauea eruption in the past 1,000 years.

The longest-known eruptive activity anywhere on Kilauea was at the lava lake in the summit caldera, which was active when missionary William Ellis visited the site in 1823, and remained mostly active until it was obliterated by an explosive eruption in 1924.

Kilauea volcano continues to pump nearly 500,000 cubic meters of magma to the surface each day, and so far the eruption has enlarged the Big Island by about 570 acres.

James Kauahikaua, scientist-in-charge at the observatory, said researchers don't know why this eruption has lasted so long after a century when Kilauea was generally characterized by shorter eruptions. "That's definitely one of the things we're working on. We'd like to know the answer, too," he said.

The current eruption began shortly after midnight on Jan. 3, 1983 with the opening of ground fissures in the midsection of Kilauea's East Rift Zone, followed by spectacular lava fountains that erupted as high as 1,500 feet at Pu'u 'O'o.

After about three years, the eruption shifted to a vent known as Kupaianaha, where it released lava for more than five years. That phase was the most destructive so far of the current eruption, wiping out homes and businesses in Kalapana.

The eruption has remained within the boundaries of Hawai'i Volcanoes National Park for most of the years that followed, but Kilauea reminded Puna residents in 2007 just how unpredictable the lava flows can be by opening new fissures west of Kupaianaha on July 21.

One of those cracks leaked lava that headed more than three miles toward the Puna population hub of Pahoa, causing some nervousness among residents. The flow was closely watched by scientists and county Civil Defense officials, but it stalled in the Wao Kele O Puna rain forest when it was still about seven miles from Pahoa Village.

In November, the fissure stopped supplying magma to the flow that had been headed toward Pahoa, and since then has mostly been oozing lava to the southwest in the general direction of the ocean.

The eruption coincided with rapid advances in the technology used to study volcanoes, technological advances that Kauahikaua said have opened new areas of inquiry.

The technology "gives us amazing new views of what's happening, which leads us to new questions," he said.

Among those improvements are advances in geologic, gas and deformation monitoring with a network of Global Positioning System equipment and webcams that allow 24-hour visual monitoring of the volcano.

Reach Kevin Dayton at kdayton@honoluluadvertiser.com.

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