Rumblings and Fire Shed No Light

The silver Hughes helicopter settled its skids on the glassy entrails of cold magma and idled its engine.

Four field geologists from the Hawaiian Volcano Observatory jumped out onto the field of black pahoehoe lava. They stumbled toward the monitoring site as quickly as they could drag their battered equipment cases across the sharp-edged spatter fissures.

Deep inside Kilauea, a half-mile beneath their feet, an immense plume of magma was on the move.

With portable tiltmeters, seismographs and satellite geodetic sensors, the scientists urgently sought the measure of that fiery serpent as it snaked its way toward the surface. By systematically recording the volcano’s erratic pulse, their field instruments could provide an early warning of any impending disaster for tens of thousands of island residents.

For the U.S. Geological Survey volcanologists, it was just another morning atop the most active volcano in the world.

In the previous 24 hours, the subterranean lava stream--an estimated 6.5 million cubic yards of new magma--had shaken the mountain’s foundations with a swarm of early morning earthquakes.

Surprisingly, the violent movement choked off the longest recorded volcanic eruption in modern times.

Kilauea, a massive shield volcano that rises almost 20,000 feet above the Pacific Ocean floor, has erupted continuously since 1983, spewing enough molten rock to bury Manhattan to a depth of 121 feet. It has spurted fountains of fire more than 1,500 feet high--three times the height of the Washington Monument--and added 547 acres of land to the island.

It has exuded so many tons of sulfur dioxide fumes that vog, as residents call the volcanic haze, is a serious air pollution problem.

But as tremors shook Kilauea early on Sept. 12, the streams of incandescent rock spewing from oceanside lava tubes seven miles from the summit abruptly dribbled to a halt. The cooling cliffs of new rock along a half-mile of the volcano’s southern coast collapsed into the surf in explosions of steam. The entire mountainside tilted.

Now the team from the volcano observatory scrambled to understand why.

On an island with so many major celestial observatories that astronomy has overtaken sugar plantations as a leading local industry, the federal observatory is unique. Its instruments are trained not on the heavens but on a portal into the Earth’s molten interior.

Yet the USGS facility is so unassuming that tourists often mistake the cluster of one-story buildings overlooking the vast, smoldering Kilauea caldera for an annex of the National Park Service museum.

With a staff of 24 and an annual budget of $2.3 million, the laboratory has been keeping a wary eye on Kilauea and four other major volcanoes on Hawaii since 1912. Like Kilauea, two of them--Mauna Loa and Hualalai--have erupted in the past 200 years.

Together, they form the southeastern end of a chain of volcanoes that began to evolve 70 million years ago, giving birth to an archipelago of islands and underwater seamounts that stretches for 4,100 miles.

Lo’ihi, the youngest, is barely 18 miles south of Hawaii. It started erupting again in 1996. Already more than two miles high, the volcano has yet to breach the ocean surface.

To assess the hazards, lab researchers have wreathed the island’s volcanoes with skeins of scientific sensors like leis.

In the coming hours, the researchers hoped their instruments would reveal whether this unexpected lull in Kilauea was part of the ongoing eruption or a harbinger of a devastating change in the volcano’s behavior.

If the recent past was any reliable guide, the long-running eruption on the eastern slope of Kilauea--called the Pu’u O’o crater--would resume within days or weeks, as it has stopped and started about 75 times in the past 16 years. Perhaps, after spewing enough lava at 2,100 degrees to consume 181 homes and 40 square miles of rain forest, Kilauea simply had exhausted itself.

But should sufficient amounts of ground water and the buried magma plume mix under pressure, the mountain also could explode so violently it might endanger the nearby port city of Hilo and the plush resorts of the Kona-Kohala coast.

For much of this century, Kilauea’s spectacular eruptions have been so relatively gentle that tourists today think nothing of hiking across its vast caldera or idling away a vacation in the suites of the Volcano House hotel on its rim.

New geological mapping and dating studies, however, recently revealed that the volcano has erupted explosively many times in the past 5,000 years. This happened most recently in 1924 and before that in 1790, when searing ash and volcanic gases killed a war party of some 80 Hawaiian soldiers.

“What this means right now, we really don’t know; there are a lot of ifs and possibilities,” said chief scientist Donald A. Swanson at the volcano observatory. He plotted the day’s research activities in an office cluttered with rolls of topographic maps, lava samples, a mound of bluejeans, old socks and four pairs of worn field boots, their soles melted from the heat of treading near lava flows.

“The main thing about studying an active volcano is that there is never a dull moment. You are always guessing and your guesses are almost always wrong,” Swanson said. Of the latest turn of events inside the volcano, he said: “My jaw dropped. I could not believe it.

“What you learn at Kilauea is that topography is ephemeral,” he said. “Terra is not firma.”

When the days wore on with only minor changes in Kilauea’s behavior, the observatory scientists used their data to reconstruct what had transpired underground.

As best they could tell, the intrusion of so much new lava had created a series of underground fissures vast enough to dramatically lower the internal pressure of the eruption. The outward tilt of the mountainside was caused when the volcano swelled to make room for the new plume.

Almost immediately, the magma chambers began to reinflate as new lava slowly filled the fissures. Even so, the eruption took much longer to resume than in the past, the scientists said.

By Sept. 27, the scientists were able to detect a series of new lava tongues emerging sluggishly from the Pu’u O’o crater below Kilauea’s summit. Slowly, the new flows neared the sea.

So much new magma was visible that they decided the pause in the eruption could be considered officially over, having lasted for almost 12 days.

Kilauea, they concluded, is still awake and fuming.

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Measuring Kilauea

The Hawaiian Volcano Observatory is monitoring the longest continuous eruption in modern times to better understand volcanic activity such as the interruption of lava flow that occurred Sept. 12.

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Source: U.S. Geological Survey, Hawaiian Volcano Observatory