Mauna Loa Volcano Eruption Update

HAWAIIAN VOLCANO OBSERVATORY WEEKLY UPDATE
Friday, September 23, 2022, 10:29 AM HST

 
An aerial view of the prominent 1940 cinder-and-spatter cone on the floor of Mauna Loa's summit caldera.
An aerial view of the prominent 1940 cinder-and-spatter cone on the floor of Mauna Loa's summit caldera. The cone, about 100 m (330 ft) high, was built during a 134-day-long eruption that began on April 7, 1940. Most of the caldera floor around the cone is covered by last lava flows erupted in 1984.

Photo courtesy of USGS

MAUNA LOA

A small seismic swarm is ongoing beneath the summit of Mauna Loa volcano. Since 2 a.m. HST on 09/23/2022, the U.S. Geological Survey’s Hawaiian Volcano Observatory has recorded over 38 earthquakes beneath the summit caldera region with most earthquakes in a cluster about 3.1 mi (5 km) wide and -1.2 to 0.6 mi (-2 to 1 km) below the surface. These earthquakes may result from changes in the magma storage system and/or may be part of normal re-adjustments of the volcano due to changing stresses within it. HVO continues to monitor Hawaiian volcanoes for any changes.

According to HVO Scientist-in-Charge Ken Hon, "Seismic activity beneath Mauna Loa has been gradually increasing over the past two months. Small earthquake swarms are considered a normal part of this increase in activity. Currently there are no indications that magma is moving toward the surface and other monitoring systems are displaying normal behavior. Levels of seismicity and deformation remain below those recorded during the winter of 2021. HVO will continue to closely monitor this activity and report any significant changes."

EARTHQUAKE SWARM DESCRIPTION

  • Magnitude Range: up to 2.7, https://earthquake.usgs.gov/earthquakes/eventpage/hv73149507
  • Date and Time: Starting at 2 a.m. HST on September 23, 2022, and ongoing
  • Location: beneath summit caldera region of Mauna Loa
  • Depth: -1.2 to 0.6 mi (-2 to 1 km) below sea level
  • Number of detected events: Over 38

For more information on current monitoring of Mauna Loa volcano visit the USGS website.



Background:
Mauna Loa is the largest active volcano on our planet, rising gradually to 4,170 meters (13,681 feet) above sea level. Its long submarine flanks descend an additional 5 kilometers (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 another 8 kilometers (5 miles). This places Mauna Loa's summit about 17,000 meters (56,000 feet) above its base. The enormous volcano covers half of the Island of Hawaiʻi and by itself amounts to about 85 percent of all the other Hawaiian Islands combined.

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 its first well-documented eruption in 1843, the volcano has erupted 33 times with intervals between eruptions ranging from months to decades. Mauna Loa last erupted 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.

Last updated: September 23, 2022

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