What’s shaking at Kīlauea Summit?

(BIVN) – Kīlauea is not erupting, and the number of earthquakes has decreased over the past 24 hours compared to the dramatic increase in seismicity that began a week ago.

The USGS Volcano Alert Level is at ADVISORY.

From this week’s Volcano Watch article, written by scientists and affiliates of the US Geological Survey Hawaiian Volcano Observatory:

Over the past week, earthquakes and inflation near Kīlauea’s summit have led to temporary closures in Hawai’i Volcanoes National Park. What’s happening beneath Kīlauea’s surface and what does this mean for possible future eruptions?

USGS: This map shows the recent unrest in Kīlauea. Yellow circles mark the locations of approximately 1,600 earthquakes that occurred between April 27 and May 2, 2024. Most earthquakes were smaller than magnitude 2, with locations clustering in an area known as the Upper East Rift Zone or East Rift Connector . This area responds to pressurization of magma chambers beneath Kīlauea’s summit region. The upper region of the East Rift Zone saw several eruptions in the 1960s and 1970s, which are labeled and shown in purple. Most recently, in November 1979, a brief one-day eruption occurred in and near Pauahi Crater. In July 1974, a three-day eruption began at Keanakāko’i Crater, with east-west oriented fissures subsequently opening at Kaluapele and southeastward to Luamanu Crater. A month-long eruption in November 1973 extended from Pauahi Crater eastward to Pu’uhuluhulu. And a daylong eruption in May 1973 extended from about half a mile (1 km) west of Hi’iaka to Pauahi Crater.

Earthquake activity in the upper East Rift Zone, immediately southeast of Kaluapele (Kīlauea’s summit caldera), increased around midnight on April 27. Since then, more than 1,600 events have been recorded, most of which extend from Keanakāko’i Crater southeast to Pauahi Crater. Most earthquakes were smaller than magnitude 2 and occurred at a depth of 2 to 3 km below the ground surface.

Patterns of ground movements are consistent with inflation of the two major magma storage areas beneath Kīlauea: Halema’uma’u and South Caldera. These magma bodies, which are long-term features of the conduit system at Kīlauea’s summit, began simultaneously re-inflating about a month after the short-lived September 2023 eruption. They then fueled the Southwest Rift Zone intrusion in late January – early February 2024. Thousands of earthquakes accompanied that intrusion as magma moved underground to the southwest, where ground deformation was significant enough to cause surface ground cracks along the Maunaiki to cause. Trail in Hawai’i Volcanoes National Park.

Since the Southwest Rift Zone invasion earlier this year, instruments are again showing signs that Kīlauea’s shallow magma conduit system is refilling. The Sand Hill tilt gauge, which is sensitive to the deeper Kīlauea magma reservoir in the South Caldera, has been showing a steady inflationary tilt since early February. Data shows that the South Caldera Reservoir has regained the volume of magma it lost during the recent intrusion, so that pressure levels are now comparable to pre-intrusion levels. The Uēkahuna tiltmeter (UWE) is more sensitive to the Halema’uma’u Reservoir, which has been the source for recent eruptions at the summit. UWE has shown slower inflation than SDH in recent months, implying that the South Caldera Reservoir is still the main focus for magmatic recharge.

During the long-lived Puʻu ʻōʻō eruption, earthquake activity in Kīlauea’s upper East Rift Zone occurred at times, along with a greater degree of tilting at Kīlauea Summit; this indicated that the summit magma reservoirs were coming under increasing pressure. When the summit lava lake was active at Halema’uma’u from 2008–2018, this increased pressure was visible as a rise in the lava lake level, with the level acting as a barometer of Halema’uma’u’s underlying magma chamber you.

USGS: A cross-section of the proposed magma conduit system beneath Kīlauea’s surface. “H” marks Halema’uma’u Reservoir; “SC” marks the southern caldera reservoir; “K” marks Keanakāko‘i Reservoir; “HKIT” notes a connection between Halema‘uma‘u Reservoir and Kīlauea Iki; SWRZ stands for the Southwestern Rift Zone. The exact depths and geometries of these connections are not well known, but this cross section represents one of the hypothesized configurations.

The current increase in earthquakes (especially in the Upper East Rift Zone) and inflation rates tell us that Kīlauea’s magma storage system is ready for its next event. One possible outcome could be another significant intrusion – when magma moves to a new area within the volcano but fails to erupt at the surface – like what occurred along the Southwestern Rift Zone has occurred. Another possible outcome could be another eruption, either inside or outside the caldera.

Kaluapele eruptions in recent years have been preceded by about an hour of rapidly occurring earthquakes and a greatly increased rate of ground deformation in the summit area as magma makes its way to the surface. An eruption outside the caldera, along one of the fault zones, would also be preceded by rapidly occurring earthquakes, together with a greatly increased rate of ground deformation in the region of magma movement outside the summit region. USGS Hawaiian Volcano Observatory (HVO) staff are monitoring closely and currently see no signs of such magma movement in the dense network of monitoring instruments on Kīlauea; currently activity is limited to the Upper East Rift Zone and the summit.

Although Kaluapele has been home to eruptions in recent years, pit craters and lava flows in the Upper East Rift Zone are evidence of a long history of magma moving along this path of the rift. Most recently, in November 1979, a brief one-day eruption occurred in and near Pauahi Crater; it was preceded by two months of 200 to 800 earthquakes daily, along with inflation in the top region.

Currently, there are no signs that an eruption is imminent; However, monitoring data from Kīlauea show that magma is once again accumulating and pressurizing in the long-lived magma bodies beneath Kīlauea’s summit. How that pressure will be lifted remains to be seen: HVO is closely monitoring multiple data sets for clues.