HILO, Hawai'i — Ten firefighters from Whiskeytown National Recreation Area in northern California arrived on the Big Island yesterday to help put out fires that might be ignited by new lava flows.

Late Monday or early Tuesday lava broke through the ground in the rainforest northeast of Kane Nui o Hamo. Park officials are making plans to fight any lava-caused fires to protect the forest.

If the lava flow does resume in the upper East Rift area near Kane Nui o Hamo, it would almost surely ignite fires that would consume pristine forest in the Hawai'i Volcanoes National Park's 2,500-acre East Rift Rainforest Special Ecological Area.

That area is considered so valuable it was fenced to protect it from invasive pigs. It provides habitat for the endangered 'io, or Hawaiian hawk, and rare plants, including Hawaiian lobeliads, mints, jewel orchids and the endangered kihi fern.

Meanwhile, park officials reopened the closed portion of Crater Rim Drive and Kilauea summit trails yesterday after sulfur dioxide emissions from Kilauea's summit caldera dropped back down to background levels.

However, parks officials reminded visitors that air quality in the area can change quickly, and advised motorists traveling along Crater Rim Drive near the South West Rift to close their windows and set their air conditioning to recirculate air within their vehicles.

Officials also advised motorists to stay in their vehicles except at designated pull-outs.

Chain of Craters Road, Hilina Pali Road and Pu'u 'O'o remained closed, as did the park's eastern boundary near Kalapana.

Much of the park is still open, including the Kilauea Visitor Center, Jaggar Museum, Thurston Lava Tube, Volcano House Hotel, Kilauea Military Camp and Volcano Art Center Gallery.

The most recent Kilauea rumblings began Sunday with a commotion of earthquakes and magma movement, and appeared to be ending the week with an eruption interruption.

U.S. Geological Survey scientists say the eruption at Pu'u 'O'o has officially "paused," with the daily flow of more than 250,000 cubic yards magma somehow cut off or diverted from what had been the focus of the eruption.

Without that magma coursing through it and on to the sea, the Pu'u 'O'o crater rapidly collapsed into itself.

Volcanic gasses and smoke billowed out of three new cracks in the upper East Rift zone, which appeared to be swelling with magma, but the only new lava flow was a small breakout late Monday or early Tuesday along one of the cracks in the rainforest northeast of Kane Nui o Hamo.

That flow didn't even last through Tuesday morning, and scientists are unwilling to venture a guess as to what Kilauea will do next, or when.

Earthquake activity and the tremor associated with magma movement decreased to a murmur late this week.

"It's fairly quiet. The tremor levels up at the summit are just slightly above background (levels) still, but they're going down," while tremors on the East Rift that were the focus of activity this week dropped to below normal levels, said David Wilson, seismic network manager for the Hawaiian Volcano Observatory.

Experts at the observatory have seen dozens of days-long pauses since the current eruption started in 1983. In some cases, such as in 1997, the eruption picked up where it left off, sending lava streaming back toward the ocean from Pu'u 'O'o.

In other cases, periods of quiet at Kilauea were followed by dramatic changes. One example was in 1992, when the Kupa'ianaha vent went silent for 10 days, and the eruption abruptly shifted to Pu'u 'O'o.

Reach Kevin Dayton at kdayton@honoluluadvertiser.com.