Mauna Loa

HAWAIIAN VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Thursday, July 22, 2021, 9:27 AM HST (Thursday, July 22, 2021, 19:27 UTC)

MAUNA LOA VOLCANO (VNUM #332020)
19°28'30" N 155°36'29" W, Summit Elevation 13681 ft (4170 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Activity Summary: Mauna Loa Volcano remains in a state of low-level unrest. Rates of seismicity at the summit remain slightly above long-term background levels. Monitoring of ground deformation, gas discharge and visual monitoring show no significant changes.

Observations:

During the past week, HVO seismometers captured 38 small-magnitude (below M2.5) earthquakes beneath the summit and upper flanks of Mauna Loa. The majority of these earthquakes occurred at shallow depths less than 8 kilometers (5 miles) below sea level.

Ground deformation, measured using Global Positioning System (GPS) measurements, confirm that the surface of the volcano has not moved appreciably over the past week.

Gas concentrations and fumarole temperatures at both the summit crater and Sulphur Cone on the Southwest Rift Zone show no unusual activity.

Finally, web-cameras showed no changes at Mauna Loa summit and on its lower flanks over the past week.

For more information on current monitoring of Mauna Loa Volcano, see: https://www.usgs.gov/volcanoes/mauna-loa/monitoring.

---

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 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.

More Information:
Mauna Loa activity summary also available by phone: (808) 967-8866
Mauna Loa webcam images: https://www.usgs.gov/volcanoes/mauna-loa/webcams
Mauna Loa photos/video: https://www.usgs.gov/volcanoes/mauna-loa/photo-video-chronology
Mauna Loa maps: https://www.usgs.gov/volcanoes/mauna-loa/maps
Mauna Loa FAQs: https://www.usgs.gov/volcanoes/mauna-loa/faqs

----------
Subscribe to these messages: https://volcanoes.usgs.gov/vns2/

Summary of volcanic hazards from eruptions: https://www.usgs.gov/observatories/hawaiian-volcano-observatory/hazards

Recent earthquakes in Hawaiʻi (map and list): https://www.usgs.gov/observatories/hawaiian-volcano-observatory/earthquakes

Explanation of Volcano Alert Levels and Aviation Color Codes: https://www.usgs.gov/natural-hazards/volcano-hazards/about-alert-levels

CONTACT INFORMATION:

askHVO@usgs.gov

The Hawaiian Volcano Observatory is one of five volcano observatories within the U.S. Geological Survey and is responsible for monitoring volcanoes and earthquakes in Hawaiʻi.