Hawaii volcano eruption enters new phase as crater falls quiet

June 1 (Reuters) - As lava continued to pour vigorously from the ground through fissures at the foot of Kilauea Volcano, the month-old eruption on Hawaii's Big Island has entered a new, seemingly calmer phase inside the summit crater, government scientists said on Friday.

But vulcanologists monitoring and measuring Kilauea's every move during the past four weeks hastened to add the latest change in the volcano's behavior, while undoubtedly significant, leaves them uncertain about what will follow.

The summit crater, which began ejecting ash and volcanic rock in periodic, daily eruptions in mid-May, has largely fallen quiet since Wednesday, Kyle Anderson, a U.S. Geological Survey (USGS) geophysicist, told reporters in a conference call.

The apparent reason, newly revealed in footage recorded by drone aircraft flown over the summit, is that tons of rocky material shaken loose from the inside walls of the crater vent have plugged up the bottom of the void, Anderson said.

What happens next is unknown.

"It's possible that new explosions will blast through the rubble at the bottom of the vent, and these may or may not be larger than previous explosions," he said. "It's also possible that the vent could become permanently blocked, ending the explosions entirely."

Related: Shocking photos of the eruption

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Volcano erupts behind golfers in Hawaii
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Volcano erupts behind golfers in Hawaii
HAWAII VOLCANOES NATIONAL PARK, HI - MAY 15: People play golf as an ash plume rises in the distance from the Kilauea volcano on Hawaii's Big Island on May 15, 2018 in Hawaii Volcanoes National Park, Hawaii. The U.S. Geological Survey said a recent lowering of the lava lake at the volcano's Halemaumau crater 'has raised the potential for explosive eruptions' at the volcano. (Photo by Mario Tama/Getty Images)
HAWAII VOLCANOES NATIONAL PARK, HI - MAY 15: People watch at a golf course as an ash plume rises in the distance from the Kilauea volcano on Hawaii's Big Island on May 15, 2018 in Hawaii Volcanoes National Park, Hawaii. The U.S. Geological Survey said a recent lowering of the lava lake at the volcano's Halemaumau crater 'has raised the potential for explosive eruptions' at the volcano. (Photo by Mario Tama/Getty Images)
HAWAII VOLCANOES NATIONAL PARK, HI - MAY 15: A man drives a golf cart at a golf course as an ash plume rises in the distance from the Kilauea volcano on Hawaii's Big Island on May 15, 2018 in Hawaii Volcanoes National Park, Hawaii. The U.S. Geological Survey said a recent lowering of the lava lake at the volcano's Halemaumau crater 'has raised the potential for explosive eruptions' at the volcano. (Photo by Mario Tama/Getty Images)
HAWAII VOLCANOES NATIONAL PARK, HI - MAY 15: Kids play at a golf course as an ash plume rises in the distance from the Kilauea volcano on Hawaii's Big Island on May 15, 2018 in Hawaii Volcanoes National Park, Hawaii. The U.S. Geological Survey said a recent lowering of the lava lake at the volcano's Halemaumau crater 'has raised the potential for explosive eruptions' at the volcano. (Photo by Mario Tama/Getty Images)
HAWAII VOLCANOES NATIONAL PARK, HI - MAY 15: Boys play at a golf course as an ash plume rises in the distance from the Kilauea volcano on Hawaii's Big Island on May 15, 2018 in Hawaii Volcanoes National Park, Hawaii. The U.S. Geological Survey said a recent lowering of the lava lake at the volcano's Halemaumau crater has raised the potential for explosive eruptions at the volcano. (Photo by Mario Tama/Getty Images)
HAWAII VOLCANOES NATIONAL PARK, HI - MAY 15: A man drives a golf cart at a golf course as an ash plume rises in the distance from the Kilauea volcano on Hawaii's Big Island on May 15, 2018 in Hawaii Volcanoes National Park, Hawaii. The U.S. Geological Survey said a recent lowering of the lava lake at the volcano's Halemaumau crater �as raised the potential for explosive eruptions�at the volcano. (Photo by Mario Tama/Getty Images)
HAWAII VOLCANOES NATIONAL PARK, HI - MAY 15: People watch at a golf course as an ash plume rises in the distance from the Kilauea volcano on Hawaii's Big Island on May 15, 2018 in Hawaii Volcanoes National Park, Hawaii. The U.S. Geological Survey said a recent lowering of the lava lake at the volcano's Halemaumau crater 'has raised the potential for explosive eruptions' at the volcano. (Photo by Mario Tama/Getty Images)
HAWAII VOLCANOES NATIONAL PARK, HI - MAY 15: A woman hold her dog Tzippy at a golf course as an ash plume rises in the distance from the Kilauea volcano on Hawaii's Big Island on May 15, 2018 in Hawaii Volcanoes National Park, Hawaii. The U.S. Geological Survey said a recent lowering of the lava lake at the volcano's Halemaumau crater 'has raised the potential for explosive eruptions' at the volcano. (Photo by Mario Tama/Getty Images)
HAWAII VOLCANOES NATIONAL PARK, HI - MAY 15: A family gathers at a golf course as an ash plume rises in the distance from the Kilauea volcano on Hawaii's Big Island on May 15, 2018 in Hawaii Volcanoes National Park, Hawaii. The U.S. Geological Survey said a recent lowering of the lava lake at the volcano's Halemaumau crater 'has raised the potential for explosive eruptions' at the volcano. (Photo by Mario Tama/Getty Images)
VOLCANO, HI - Foreign tourists climb trees on the 18th hole of the Volcano Golf and Country Club to view the plumes of smoke coming from the Halemaumau Vent of the Kilauea Volcano in Volcano, HI on May 15, 2018. It is reportedly spewing only ash at this time and no large rocks. (Photo by Linda Davidson / For The Washington Post via Getty Images)
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In any case, the volcano's behavior ultimately hinges on the ebb and flow of huge rivers of molten rock called magma, the term for lava while it remains underground.

The steady collapse of the crater's inner walls, caused by magma draining out of the summit and oozing downslope under the volcano's surface, has also greatly enlarged the mouth of the vent, which has grown in size from about 12 acres (4.9 hectares) to 120 acres (48.5 hectares), Anderson said.

At the same time, the Kilauea summit itself has sunken, or subsided, by at least 5 feet (1.50 meters) in elevation as the magma level continues to drop, exerting tremendous pressure on seismic faults to create numerous earthquakes, mostly small tremors, in the immediate vicinity.

Although the summit crater of Kilauea has fallen silent for the moment, many of the two dozen volcanic fissures running through populated areas on its eastern flank continued to spout and ooze lava and toxic gases that prompted the evacuation of some 2,500 residents. At least 75 homes -- most of them in the hard-hit community of Leilani Estates -- have been devoured by streams of red-hot molten rock creeping across the landscape since May 3. Lava flows also have knocked out power and telephone lines in the region, disrupting communications.

Another issue has been the occurrence of a phenomenon called Pele's hair -- fine, glass-like fibers of volcanic material produced by fountains of lava and carried aloft by the wind. The filament, named for the mythical goddess of volcanoes, can cause skin, eye and respiratory irritation like fiberglass.

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19 PHOTOS
Images of Kilauea volcano eruption
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Images of Kilauea volcano eruption
Lava erupts on the outskirts of Pahoa during ongoing eruptions of the Kilauea Volcano in Hawaii, U.S., May 19, 2018. REUTERS/Terray Sylvester
Lava flows through trees on the outskirts of Pahoa during ongoing eruptions of the Kilauea Volcano in Hawaii, U.S., May 19, 2018. REUTERS/Terray Sylvester
Lava erupts on the outskirts of Pahoa during ongoing eruptions of the Kilauea Volcano in Hawaii, U.S., May 19, 2018. REUTERS/Terray Sylvester
Lava erupts on the outskirts of Pahoa during ongoing eruptions of the Kilauea Volcano in Hawaii, U.S., May 18, 2018. REUTERS/Terray Sylvester TPX IMAGES OF THE DAY
Lava flows through forest on the outskirts of Pahoa during ongoing eruptions of the Kilauea Volcano in Hawaii, U.S., May 18, 2018. REUTERS/Terray Sylvester
Gas erupts from a lava flow on the outskirts of Pahoa during ongoing eruptions of the Kilauea Volcano in Hawaii, U.S., May 18, 2018. REUTERS/Terray Sylvester
Lava flows past trees on the outskirts of Pahoa during ongoing eruptions of the Kilauea Volcano in Hawaii, U.S., May 18, 2018. REUTERS/Terray Sylvester
Lava flows through forest on the outskirts of Pahoa during ongoing eruptions of the Kilauea Volcano in Hawaii, U.S., May 18, 2018. REUTERS/Terray Sylvester
Lava erupts on the outskirts of Pahoa during ongoing eruptions of the Kilauea Volcano in Hawaii, U.S., May 18, 2018. REUTERS/Terray Sylvester
KAPOHO, HI - MAY 20: A lava fountain from a Kilauea volcano fissure erupts, while forming a new cone, on Hawaii's Big Island on May 20, 2018 in Kapoho, Hawaii. The U.S. Geological Survey said the volcano erupted explosively on May 17 launching a plume about 30,000 feet into the sky. (Photo by Mario Tama/Getty Images)
KAPOHO, HI - MAY 19: Residents view lava erupting from a Kilauea volcano fissure, at a small viewing party on a neighbor's porch, on Hawaii's Big Island on May 19, 2018 in Kapoho, Hawaii. Some local residents have held small viewing parties to view lava. The U.S. Geological Survey said the volcano erupted explosively on May 17 launching a plume about 30,000 feet into the sky. (Photo by Mario Tama/Getty Images)
KAPOHO, HI - MAY 19: A bird rests on a wire as lava from a Kilauea volcano fissure erupts on Hawaii's Big Island on May 19, 2018 in Kapoho, Hawaii. The U.S. Geological Survey said the volcano erupted explosively on May 17 launching a plume about 30,000 feet into the sky. (Photo by Mario Tama/Getty Images)
KAPOHO, HI - MAY 19: Lava from a Kilauea volcano fissure flows on Hawaii's Big Island on May 19, 2018 in Kapoho, Hawaii. The U.S. Geological Survey said the volcano erupted explosively on May 17 launching a plume about 30,000 feet into the sky. (Photo by Mario Tama/Getty Images)
KAPOHO, HI - MAY 19: A young resident keeps an eye on lava from a Kilauea volcano fissure erupting and flowing near her home on Hawaii's Big Island on May 19, 2018 in Kapoho, Hawaii. The U.S. Geological Survey said the volcano erupted explosively on May 17 launching a plume about 30,000 feet into the sky. (Photo by Mario Tama/Getty Images)
KAPOHO, HI - MAY 18: A man takes a photo of a lava fountain from a Kilauea volcano fissure on Hawaii's Big Island on May 18, 2018 in Kapoho, Hawaii. The U.S. Geological Survey said the volcano erupted explosively on May 17 launching a plume about 30,000 feet into the sky. (Photo by Mario Tama/Getty Images)
KAPOHO, HI - MAY 18: Lava erupts and flows from a Kilauea volcano fissure as trees burn on Hawaii's Big Island on May 18, 2018 in Kapoho, Hawaii. The U.S. Geological Survey said the volcano erupted explosively on May 17 launching a plume about 30,000 feet into the sky. (Photo by Mario Tama/Getty Images)
KAPOHO, HI - MAY 18: Lava erupts and flows from a Kilauea volcano fissure on Hawaii's Big Island on May 18, 2018 in Kapoho, Hawaii. The U.S. Geological Survey said the volcano erupted explosively on May 17 launching a plume about 30,000 feet into the sky. (Photo by Mario Tama/Getty Images)
KAPOHO, HI - MAY 18: Lava erupts and flows from a Kilauea volcano fissure on Hawaii's Big Island on May 18, 2018 in Kapoho, Hawaii. The U.S. Geological Survey said the volcano erupted explosively on May 17 launching a plume about 30,000 feet into the sky. (Photo by Mario Tama/Getty Images)
KAPOHO, HI - MAY 18: Lava erupts and flows from a Kilauea volcano fissure on Hawaii's Big Island on May 18, 2018 in Kapoho, Hawaii. The U.S. Geological Survey said the volcano erupted explosively on May 17 launching a plume about 30,000 feet into the sky. (Photo by Mario Tama/Getty Images)
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Residents have been warned to avoid exposure to Pele's hair, one of several airborne volcano hazards including emissions of sulfur dioxide gas, wind-blown ash and noxious clouds of laze -- a term combining the words "lava" and "haze" -- formed when lava reacts with seawater to form a mix of acid fumes, steam and glass-like specks.

The latest upheaval of Kilauea, one of the world's most active volcanoes, comes on the heels of an earlier eruption cycle that began in 1983 and continued almost nonstop for 35 years, destroying 215 dwellings and other structures. (Reporting by Steve Gorman in Los Angeles; Editing by Sandra Maler)

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