USGS-HVO Mauna Loa Weekly Update

Activity Summary: Mauna Loa Volcano 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. Observations: An earthquake swarm occurred southwest of Mauna Loa’s summit on April 16th-17th. During the past week, HVO seismometers recorded approximately 175 small-magnitude earthquakes below Mauna Loa, most concentrated below the summit and upper-elevation flanks of the volcano. Nearly all of the earthquakes were less that M3 and occurred mostly at depths of less than 8 km (about 5 mi) below ground level. Global Positioning System (GPS) measurements continue to show a slightly extensional summit deformation pattern over the past week. Gas concentrations (0 ppm SO2) and fumarole temperatures (below 100 degrees Celsius or 212 degrees Fahrenheit) 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. For more information on current monitoring of Mauna Loa Volcano, see: https://volcanoes.usgs.gov/volcanoes/mauna_loa/monitoring_summary.html ----- Background: Mauna Loa is the largest active volcano on our planet, rising gradually to 4,170 m (13,681 ft) above sea level. Its long submarine flanks descend an additional 5 km (3 mi) below sea level to the ocean floor. The ocean floor directly beneath Mauna Loa is, in turn, depressed by the volcano's great mass another 8 km (5 mi). This places Mauna Loa's summit about 17,000 m (56,000 ft) above its base. The enormous volcano covers half of the Island of Hawaiʻi. 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 Zone. Since 1843, the volcano has erupted 33 times with intervals between eruptions ranging from months to decades. Mauna Loa last erupted 37 years ago, in 1984. Mauna Loa eruptions 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: in 1859, 1868, 1887, 1926, 1919, and three times in 1950. ---- This image is from a research camera positioned on the south rim of Mokuʻāweoweo, Mauna Loa's summit caldera, in Hawaiʻi Volcanoes National Park. The camera looks north-northwest, focusing on the southern part of the caldera. The 1940 cone is just right of center; the 1949 cone is on the caldera rim at left. The high point of Mauna Loa's summit is in the background.