Elevated seismicity and deformation at the summit of Mauna Loa volcano, Hawaii

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While the largest volcano on Earth — Mauna Loa is not erupting, rates of deformation and seismicity at the summit remain slightly elevated and above long-term background levels. Other Mauna Loa monitoring data streams show no significant change in deformation rates or patterns that would indicate increased volcanic hazard at this time, the Hawaiian Volcano Observatory (HVO) reported in their weekly update released on April 15, 2021.

During the past week, HVO seismometers recorded approximately 220 small-magnitude earthquakes below Mauna Loa, most concentrated below the summit and upper-elevation flanks of the volcano.

All of the earthquakes were less than M2.5 and occurred mostly at depths of less than 8 km (about 5 miles) below ground level.

Global Positioning System (GPS) measurements have recently shown variability in summit deformation patterns, moving from contractional to slightly extensional over the past week.

Gas concentrations (0 ppm SO2) and fumarole temperatures (below 100 °C or 212 °F) at both the summit and at Sulphur Cone on the Southwest Rift Zone remain stable.

Webcam views have shown no changes to the volcanic landscape on Mauna Loa over the past week.

Mauna Loa is the largest active volcano on our planet, rising gradually to 4 170 m (13 681 feet) above sea level. Its long submarine flanks descend an additional 5 km (3 miles) below sea level to the ocean floor.

The ocean floor directly beneath Mauna Loa is, in turn, depressed by the volcano's great mass of another 8 km (5 miles). This places Mauna Loa's summit about 17 km (56 000 feet) above its base. The enormous volcano covers half of the Island of Hawaiʻi.

The volcano last erupted in 1984, 35 years ago.

Eruptions typically start at the summit and, within minutes to months of eruption onset, about half of the eruptions migrate into either the Northeast or Southwest Rift Zones.

Since 1843, the volcano has erupted 33 times with intervals between eruptions ranging from months to decades.

Eruptions at Mauna Loa tend to produce voluminous, fast-moving lava flows that can impact communities on the east and west sides of the Island of Hawaiʻi. Since the mid-19th century, the city of Hilo in east Hawaiʻi has been threatened by seven Mauna Loa lava flows.

Mauna Loa lava flows have reached the south and west coasts of the island eight times: 1859, 1868, 1887, 1926, 1919, and three times in 1950.

Alert Level remains at Advisory, and Aviation Color Code at Yellow since July 2, 2019.

On July 2, 2019, HVO said earthquake and ground deformation rates at Mauna Loa Volcano have exceeded long-term background levels over the past several months, adding that eruption is not imminent and current rates are not cause for alarm. However, they do indicate changes in the shallow magma storage system at Mauna Loa.

Featured image: Mauna Loa on April 15, 2021. Credit: Copernicus EU/Sentinel-2, TW

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