USGS Drops Kīlauea Volcano Alert Levels From ‘Warning’ to ‘Watch’

The U.S. Geological Survey has changed the alert levels for the Kīlauea Volcano from WARNING to WATCH.

The fissure 8 cinder cone is currently about 30 m (100 ft) tall with a very broad base. Sulfur dioxide (SO2) emissions are low, reflecting the diminished activity of the lava ponds in the cone. Click to enlarge. PC: USGS

In light of the reduced eruptive activity at Kīlauea Volcano over the last several days, HVO is lowering the Alert Level for ground based hazards. This change indicates that the hazards posed by crater collapse events (at the Kīlauea summit) and lava flows (Lower East Rift Zone; LERZ) are diminished. However, the change does not mean with absolute certainty that the LERZ eruption or summit collapses are over. It remains possible that eruption and collapse activity could resume.

Although no signs of imminent hazardous activity are present at this time, residents of the region near recently active fissures should stay informed, heed Civil Defense warnings, and be prepared, if necessary, to self-evacuate.

The aviation color code remains at ORANGE.

Kīlauea Volcano has remained quiet for well over a week now, with no collapse events at the summit since Aug. 2, 2018. Except for a small, crusted-over pond of lava deep inside the Fissure 8 cone and a few scattered ocean entries, lava ceased flowing in the LERZ channel on Aug. 6. Sulfur dioxide (SO2) emissions rates at the summit and LERZ are also drastically reduced (the combined rate is lower than at any time since late 2007).

It remains too soon to tell if this diminished activity represents a temporary lull or the end of the LERZ lava flows and/or summit collapses. In 1955, similar pauses of five and 16 days occurred during an 88-day-long LERZ eruption. During the Mauna Ulu eruption (1969-1974), a 3.5 month pause occurred in late 1971.

HVO will continue to record detailed visual observations and scrutinize incoming seismic, deformation, and gas data, looking for evidence of significant movement of magma or pressurization as would be expected if the system was building toward renewed activity.

Ongoing Hazards

Whether this is a pause or truly the end of the current eruption, certain hazardous conditions remain in the LERZ and at the summit as described below:

The new lava flow field in the LERZ includes large areas of still-hot, rugged, and unstable lava surfaces that are subject to collapse.

SO2 gas emissions have greatly decreased from LERZ vents, but high levels of SO2 may persist in downwind areas.

Around Fissure 8, thick accumulations of tephra hide underground hazards such as holes and cracks; winds can pick up glassy fragments including Pele’s hair and carry them downwind.

At the LERZ ocean entry, laze and lava delta collapses remain a concern. Hydrovolcanic explosions may still occur during collapses of lava deltas in areas where the coastline has extended.

At the summit, rockfalls and ground cracking can still occur with no warning. Steep crater walls destabilized by months of earthquakes could be prone to collapse for weeks or months to come, even without further ground shaking.

Resuspended ash in the summit region and Pele’s hair in the LERZ remain a local hazard during strong winds.

As the summit continues to adjust to recent changes, additional, and potentially damaging, earthquakes are possible. Hawai’i is known for frequent earthquakes, so all residents should always be prepared for damaging earthquakes.

If the Kīlauea eruption in the LERZ does resume in the coming days, the USGS expect, but cannot guarantee, that increases in seismicity, deformation, and/or gas emissions will provide advance warning. Activity could resume quickly and residents in the LERZ should be prepared to self-evacuate. Resupply of magma to the LERZ could lead to new areas being inundated by lava.

At Kīlauea’s summit, further draining of the magma reservoir could produce more collapse events. Alternatively, resupply of magma to the summit reservoir could lead to hydrovolcanic explosions, or, to the reappearance of lava in the caldera.

This 3-dimensional computer model shows the structure of the Fissure 8 cone on Kīlauea Volcano’s lower East Rift Zone. The model was created from thermal images acquired during a helicopter overflight on Aug. 15, 2018.

The cone is currently about 30 m (100 ft) tall with a broad base. The bright white area within the cone is a small pond of lava, now largely crusted over, which is currently at a level near that of the pre-eruption ground surface. The open side of the cone is the spillway where lava, during the height of the eruption, flowed from the vent into the channel that transported molten lava about 13 km (8 mi) to the sea.