Scientists detail the details of the Kilauea magma breakthrough

Scientists detail the details of the Kilauea magma breakthrough

USGS: “Pu’ukoa’e, located in the southwest rift zone of Kīlauea, is prominently visible in this aerial image taken on February 6, 2024. The slopes of Mauna Loa and the Nīnole Hills are visible in the background.” (USGS photo by H. Winslow)

(Bevin) – Kīlauea is not erupting, and its USGS volcano alert level remains at ADVISORY, as earthquakes continue to decrease after magma intruded into the area last week.

From this week Volcano monitoring Article written by scientists from the US Geological Survey, Hawaiian Volcano Observatory and its affiliates:

Last week, USGS scientists at the Hawaiian Volcano Observatory (HVO) were closely monitoring earthquakes and ground deformation in the area southwest of Kīlauea Peak. Increased turbulence prompted HVO to raise the alert level/aviation color code for Kīlauea to WATCH/ORANGE on January 31 as another subsurface intrusive event began.

Intrusions occur when magma breaks down rocks to create new paths within the Earth. As magma moves below the surface to its new space, the ground above it deforms to accommodate the new material. The HVO system detects intrusions through the locations of earthquakes (which occur when rocks break) and changes in the Earth’s surface, known as deformation (which can be recorded using inclinometers, GPS, and satellite-based methods).

Earthquake swarms began south of Kilauea caldera over the weekend, January 27. This activity is not surprising, as intermittent earthquake swarms have been occurring in the southern caldera since October 2023, and there is a known pool of magma in this area.

However, on January 31, seismic activity increased significantly, with more than 700 earthquakes detected throughout the day. The number of actual earthquakes is likely much larger, as many of the smallest quakes went undetected in the swarm of intense activity.

Concurrent with the increased earthquake activity, inclinometers at Oikahuna Bluff (Kīlauea Peak) and Sand Hill (southwest of the caldera) began to show changes in the Earth’s surface. Beginning at 4:30 a.m. GMT in the morning, inclinometers began to show highly variable trends and rates, indicating fracture growth that could precede an eruption or intrusion. Increased seismic activity and complex tilt patterns prompted HVO to raise the alert level/aviation color code for Kīlauea to WATCH/ORANGE at 4:41 a.m. GMT.

Image from an interactive USGS map showing the location of the most recent seismic activity south of the Kīlauea caldera on February 2, 2024.

HVO seismologists have been analyzing the locations of the earthquakes in real time. Earthquakes beneath Halemaʻumaʻu may indicate the possibility of an eruption there (as occurred in the hours before the recent eruptions at Halemaʻumaʻu). HVO geologists, who specialize in volcanic gas, positioned themselves at the edge of the Kīlauea caldera, ready to collect data in the event of a new eruption.

However, the earthquake sites migrated to the southwest, along the Koaʻe fault system. By the evening, inclinometers showed a more consistent deflationary signal. Together, the two sets of observational data indicated that the magma had opened a new pathway and was moving from the storage system below Kīlauea Peak to the southwest.

These observations were later confirmed using satellite-based InSAR data, which showed that between 6pm GMT on January 31 and 6pm GMT on February 1, 2024, the Kilauea summit area contracted as the southwestern region rose (ma It reaches about 50 cm, or 20 degrees). inches) and spread. In the center of the uplifted area, there is a narrow band of subsidence marks where the dike (a vertical sheet of magma) protrudes, with a small portion of land subsident to accommodate lateral spreading.

USGS: “This map shows recent unrest at Kīlauea volcano. Yellow circles indicate the locations of earthquakes from January 31, 2024, to February 3, 2024, as recorded by HVO seismometers. Colored edges indicate areas of ground deformation over a 1-day time frame from 6pm GMT on January 31 to 6pm GMT on February 1, 2024. More ridges indicate more deformation. Complex patterns indicate overall contraction of the summit area as underground magma moves to the southwest, with the patterns showing uplift and spreading (side along with subsidence) due to the breach of the dike (a vertical sheet of magma).”

On February 2, the numbers of earthquakes began to decrease, along with the rates of ground deformation. On the morning of 3 February, the HVO lowered the alert level/aviation color code for Kīlauea to ADVISORY/WATCH.

Although several intrusions into Kilauea’s southern caldera have occurred recently—in December and October 2023, 2021, and 2015—the most recent incursion has extended to the southwest, toward Pukua and the Kamakaya Hills in Kilauea’s southwest rift zone. As a result of intrusion, shallow fissures, extending tens of meters in length and centimeters (inches) in width, have formed in the loose Keanakākoʻi tephra along the Maunaiki Trail near Twin Pit Craters in the Kaʻū Desert in Hawaii Volcanoes National Park.

USGS: “Aerial view of twin craters near Muniki Trail in the Ka’u Desert in Hawaii Volcanoes National Park.” (USGS photo by K. Mulliken)

The Southern Caldera Zone and the Kwai Fault System are informal names for specific geographic regions that we see on Kilauea’s surface, but which extend below the surface. There is a known magma body beneath the southern caldera (Kīlauea’s largest magma storage area) and the Koaʻe faults are structural features associated with Kīlauea’s southern flank. How these subsurface features relate to each other and to Kilauea’s southwestern rift zone is not well understood.

Intrusions are a common process encountered by volcanoes around the world, and are similar to a pressure release valve for a magma reservoir. Although Kīlauea has not had an eruption since September 2023, the latest breakthrough shows us that the volcano has been very busy below the surface.

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