Late afternoon mist moving west across the caldera produced a rainbow above Halema‘uma‘u during today’s visit to measure the water level. The water continues to slowly rise. USGS photo by M. Patrick.

(BIVN) – Kīlauea is not erupting, and the Volcano Alert Level remains at NORMAL / GREEN.

In its monthly activity update posted on Wednesday, May 6, the USGS Hawaiian Volcano Observatory reported monitoring data for the previous month “show variable but typical rates of seismicity and ground deformation, low rates of sulfur dioxide emissions, and only minor geologic changes since the end of eruptive activity in September 2018.”

Here are the complete observations shared by the HVO scientists:

Rates of seismicity over the month were about 25 per cent lower than during the past month. Sulfur dioxide emission rates are low at the summit and are below detection limits at Puʻu ʻŌʻō and the lower East Rift Zone. The crater lake at the bottom of Halema’uma’u continues to slowly expand and deepen. As of May 3rd, the lake depth was approximately 35 meters or 115 feet.

The lake was more brown in color than the last visit, with a sharp color boundary cutting across the lake. Color variations like this are common. USGS photo by M. Patrick.

Over the past month, the summit tiltmeter recorded 4 deflation-inflation events–down from 10 recorded last month. In April 2020, deformation rates at Kilauea’s summit and middle East Rift Zone continue to show inflation, consistent with magma supply to the volcano’s shallow storage system. Gas measurements show continuing low levels of sulfur dioxide emission from the Halema’uma’u area, consistent with no significant shallowing of magma. Some amount of sulfur dioxide is being dissolved into the summit lake and work continues to try and quantify this process. The lake was last sampled by UAS in January and additional sampling with UAS is planned.

On April 16, 2020, an HVO technician inspected a crack that has been widening near a power hub on Pu‘u ‘Ō‘ō. Rockfalls from the north rim of Pu‘u ‘Ō‘ō (where the hub is located) have caused the rim to recede, and it is now very close to the power/communications hub.

Farther east, GPS stations and tiltmeters continue to show motions consistent with slowed refilling of the deep East Rift Zone magmatic reservoir in the broad region between Puʻu ʻŌʻō and Highway 130. The decrease in deformation rates at tilt station POO, observed in February, continued through April. GPS station JOKA, and tilt station JKA, in the lower East Rift Zone, experienced another episode of deformation through April with a different direction from the longer term trend. Monitoring data do not suggest any imminent change in volcanic hazard for this area. The south flank of Kīlauea continued to creep seaward at elevated rates following the May 4, 2018 M6.9 earthquake near Kalapana. HVO continues to carefully monitor all data streams along the Kīlauea East Rift Zone and south flank for important changes.

Although not currently erupting, areas of persistently elevated ground temperatures and minor release of gases are still found in the vicinity of the 2018 lower East Rift Zone fissures. These include steam (water), very small amounts of hydrogen sulfide, and carbon dioxide. These conditions are expected to be long-term. Similar conditions following the 1955 eruption continued for years to decades.

Hazards: Hazards remain in the lower East Rift Zone eruption area and at the Kīlauea summit. Residents and visitors near the 2018 fissures, lava flows, and summit collapse area should heed Hawaii County Civil Defense and National Park warnings. Lava flows and features created by the 2018 eruption are primarily on private property and persons are asked to be respectful and not enter or park on private property.

The Hawaiian Volcano Observatory (HVO) continues to closely monitor geologic changes, seismicity, deformation, and gas emissions for any sign of increased activity at Kīlauea. HVO maintains visual surveillance of the volcano with web cameras and field visits. Additional messages and alert level changes will be issued as warranted by changing activity.