Kīlauea alert level lowered with end of middle East Rift Zone eruption

The Hawaiian Volcano Observatory is lowering the Volcano Alert Level for the Big Island’s Kīlauea volcano back to advisory and aviation color code from orange to yellow, reporting that the middle East Rift Zone eruption that began Sept. 15 has ended.

The eruption saw 4 phases in and near Nāpau Crater between the night of Sept. 15 and morning of Sept. 20, in a remote and closed area within Hawaiʻi Volcanoes National Park.

The last activity seen was from a small vent west of the crater, which ended at about 10 a.m. Sept. 20.

Only a couple of intermittent small spots of residual glow could be detected on the flow field Sunday night. Weak degassing from the vent continues, with the gas plume moving to the southwest this morning.

It was producing about 80 tonnes per day of sulfur dioxide as last measured Sept. 21, a substantial decrease from 30,000 tonnes per day recorded Sept. 19.

“All observable and instrumental signs of potential for renewed eruptive activity have declined since that time,” said an 8:12 a.m. volcanic activity notice today from the Hawaiian Volcano Observatory. “Seismicity in the area is extremely low and tremor, characteristic of magma within vents, is no longer being recorded by seismometers in the area.”

There were only about 13 shallow earthquakes in the middle East Rift Zone during the past 24 hours.

Ground deformation data that showed magma was moving from the summit to the middle East Rift Zone also slowed dramatically or stopped altogether and even volcanic gas emissions decreased to near background levels.

“All of these factors indicate that this eruption has ended,” the observatory’s notice said.

A webpage with eruption-related resources is available, and a summary of the eruption is available in this “Volcano Watch.”

Lava flows from the eruption covered about 2/3 of the Nāpau Crater floor — or 125 acres. The eruption covered a total of more than 156 acres of Nāpau Crater and areas to the west.

The Hawaiian Volcano Observatory remains in close contact with the national park and Hawai‘i County Civil Defense. It continues to closely monitor Kīlauea and will adjust the alert level and aviation color code accordingly.

For more information about the meaning of volcano alert levels and aviation color codes, click here.

Should volcanic activity change significantly, a new volcanic activity notice will be issued.

Hazards also remain despite the eruption’s end.

Hot and glassy, or sharp, surfaces can cause serious burns, abrasions and lacerations upon contact with unprotected or exposed skin.

Lava near vents also tends to be unstable and can easily collapse. Minor to severe ground fractures and subsidence features near the eruption site can continue to widen and offset and could have unstable overhanging edges.

This uneven and rough terrain can lead to falls and other injuries.

Gas levels, while greatly reduced from eruptive gas levels, can also continue to pose hazards to those close to vents.

For more about Kīlauea hazards, click here.

Visit the Hawaiʻi Volcanoes National Park website for visitor information. 

No changes have been detected in the lower East Rift Zone or Southwest Rift Zone of the volcano.

Six small, shallow earthquakes were detected beneath the Kīlauea summit region during the past 24 hours.

The tiltmeter at Uēkahuna remains flat, showing no deflation. The summit tiltmeter at Sandhill continues to record very weak deflation, but at a rate that is less than 10% of that recorded during the recent eruption.

This pattern suggests that very little if any magma is moving from the summit to the middle East Rift Zone.

The most recent measurement of SO2 emission rate at the summit was 60 tonnes per day on Sept. 17.

Kīlauea updates will continue to be issued daily. Regularly scheduled updates are posted on the Hawaiian Volcano Observatory website.