In the 35 years since Kilauea Volcano began its current eruption, scientists have studied its subterranean plumbing system in depth.

They knew from the recent flurry of earthquakes on the East Rift Zone and lava activity at the volcano’s summit and Puu Oo vent that magma was on the move and more volcanic fireworks could be in store.

But they didn’t know just how far the magma would travel underground before it burst into the air. The several fissures that skewered Leilani Estates late in the week, sending residents packing, are roughly 10 miles from Puu Oo.

“The remarkable part of this eruption is we had two active eruptions going on already,” said Michael O. Garcia, a geology professor at the University of Hawaii at Manoa, referring to the summit and Puu Oo. “The surprise was that the volcano decided that it wanted to form a new area of activity.”

Kilauea has been erupting since January 1983, when fissures on the East Rift Zone began spewing lava and eventually created the cinder-and-spatter cone known now as Puu Oo. Since 1983, voluminous lava from Kilauea has buried more than 50 square miles of land while also creating more than 400 acres of new land on the coast.

When Puu Oo started inflating in mid-March, a sign of pressure building beneath the vent, volcanologists anticipated action in the vicinity.

“Every time we’ve seen that in the past, eventually a new vent has formed, usually nearby, within a few kilometers of Puu Oo,” said Mike Poland, a geophysicist with the U.S. Geological Survey. “To see the magma travel so far from Puu Oo within the rift zone was a surprise.”

The fissures in Leilani Estates are all relatively short, measuring 100 to 200 yards, with low-level spattering of lava that reached tens of feet in the air, Poland said. In 1960, a 900-yard fissure near Kapoho spewed lava fountains as high as 300 feet.

In fissure-type eruptions, pressure builds within the volcano and forms cracks along the surface. Magma works its way up to the surface and erupts along the cracks, Garcia said. So far, no significant lava flows have formed from the new fissures.

Deep network

The magma plumbing system of Kilauea, a shield volcano on the eastern slope of Mauna Loa, reaches more than 35 miles into the earth, according to the U.S. Geological Survey. Among the most active volcanoes in the world, Kilauea has a deep, internal network of magma chambers and lava tubes.

Those subterranean tubes can carry lava flows far from their source. Eruptions from the flank vents of Puu Oo have sent lava miles to the ocean.

A fissure eruption in March 2011 at Puu Oo started small and died out within hours and then came roaring back and lasted for days, Poland said.

“What’s happening now with these little fissures is not so uncommon,” Poland said. “The question we deal with now is how will this evolve?”

“One possibility is we’re getting rid of the gassy top of the magma that moved down into Leilani, and the remaining magma will stagnate and freeze in place and the eruption will stop,” he said. “But it is also possible that more magma will feed into this area and the eruption will grow and strengthen. And it’s very difficult to know right now what the most likely outcome is.”

Seismic activity

The magnitude of the earthquakes at Kilauea on Friday — reaching as high as 6.9 on the Richter scale — was remarkable. The last time Kilauea had an earthquake that large was in 1975.

“Typically, the larger earthquakes are on the flanks,” Garcia said. “As you pump magma into the rift zones, the volcano slides toward the ocean.”

Janet Babb, a geologist at the Hawaiian Volcano Observatory, found the extent of seismic activity notable and said residents should heed Civil Defense advice because new fissures can open with little warning.

“What’s remarkable today is the stresses produced on the rift zone are causing some adjustments on the south flank of the volcano and we are experiencing one earthquake after another,” she said. “We are still feeling them.”

More outbreaks of lava are expected. Many people are wondering how long this new phase of the eruption will last. But that’s anyone’s guess.

“There really is no way to forecast that,” Babb said.