VOLCANOWatch: Recent Activity Reminds Us to Maintain Our Volcano Awareness

Though there hasn’t been an eruption in Hawai‘i in 2020, the year has hardly been quiet—earthquake swarms, an elevated alert-level on Mauna Loa, and a growing water lake on Kīlauea are reminders that island residents should be aware of Hawaiʻi’s active volcanoes.

In January 2021, the USGS Hawaiian Volcano Observatory (HVO) will spearhead Hawaiʻi’s 12th annual “Volcano Awareness Month,” during which residents will have an opportunity to learn more about Hawaiian volcanoes.  Unlike previous years which featured in-person presentations and field trips by HVO staff and cooperators—County of Hawai‘i Civil Defense Agency, University of Hawai‘i at Hilo, and Hawai‘i Volcanoes National Park—activities this year will be “virtual” due to the pandemic. 

Volcano Awareness Month was established in 2010 through a County of Hawai‘i proclamation to encourage “knowledge and awareness of Hawaiian volcanoes and the proper safety measures to follow beforeduring, and after a volcanic eruption.”  

Although we’re currently in the period after Kīlauea’s 2018 eruption and Mauna Loa’s 1984 eruption, recent activity at both volcanoes reminds us that we’re also in the period before the next eruption in Hawai‘i.   

Let’s look back at this past, relatively quiet year to review volcanic activity and why volcano awareness remains important. 

Despite low volcanic gas emission rates, sulfur smells were occasionally noted by Hawaiʻi residents. Residents also reported over 100 felt earthquakes in 2020. Earthquake swarms near Pāhala, Lō‘ihi Seamount, Nāmakanipaio campground, and Kīlauea’s summit prompted information statements from HVO. Monitoring data indicated that magma is slowly being supplied to Kīlauea and Mauna Loa. The water lake that appeared at the summit of Kīlauea in mid-2019 continues to grow in size and depth. 

More recently, between Nov. 30 and Dec. 2, several hundred earthquakes occurred 1–4 km (1–3 mi) beneath Kīlauea’s summit and upper East Rift Zone. On Dec. 2, a transient increase in ground deformation resulted in about 8 cm (3 inches) of uplift of the caldera floor. This was about 4 months-worth of uplift in just 4 hours. Monitoring data from Kīlauea’s summit region indicated that a small injection of magma intruded below the surface of the volcano. Although magma didn’t make it to the surface, this event demonstrated that magma continues to refill the storage system within the volcano. Next week’s “Volcano Watch” will provide more information on this activity. 

A magnitude-4.1 earthquake beneath the northwest flank of Mauna Loa on Dec. 4, along with nearby clusters of small earthquakes, remind us that Earth’s largest active volcano continues to show signs of unrest. These earthquakes were located in an area where, over the past several years, persistent minor seismicity (generally smaller than magnitude-2) has occurred. Elevated seismic activity is one reason that Mauna Loa’s volcano alert-level has been ADVISORY—“volcano is exhibiting signs of elevated unrest above known background activity”—since July 2019.  

The last time an earthquake of similar magnitude and depth occurred in this area of Mauna Loa, approximately 5 km (3 miles) northwest of Moku‘āweoweo, was November 2011, when increased rates of minor seismicity were also occurring. In 2011, other monitoring data streams remained stable and an eruption did not occur. Current data streams on Mauna Loa also remain stable and do not indicate that an eruption is imminent. 

These 2020 events remind us that Kīlauea and Mauna Loa will erupt again and that we should be informed and prepared for potential hazards associated with a restless or erupting volcano. In January 2021, video recordings of Volcano Awareness Month programs will be posted to the HVO website so that they can be viewed safely from home. 

On each Tuesday in January, a 30–45-minute video presentation by HVO scientists will be posted at usgs.gov/hvo. Topics include a Kīlauea rift zone update (Jan. 5); Kīlauea summit water lake summary (Jan. 12); description of ground deformation and earthquakes at Kīlauea over the past year (Jan. 19); and discussion of Mauna Loa’s eruptive history and current status (Jan. 26). HVO will also post shorter video presentations throughout the month. 

Whether you’re in Hawai‘i or elsewhere in January, you’ll be able to virtually and safely participate in Volcano Awareness Month. The full schedule of 2021 programs will be posted on HVO’s website later this month. 

Volcano Activity Updates 

Kīlauea Volcano is not erupting. Its USGS Volcano Alert level remains at NORMAL. Kīlauea updates are issued monthly.   

Kīlauea monitoring data for the past month show variable rates of seismicity and ground deformation, low rates of sulfur dioxide emissions, and only minor geologic changes since the end of eruptive activity in September 2018. A Kīlauea Information Statement on Dec. 3 summarized increased seismicity beneath the summit during Nov. 29–Dec. 3. Ground deformation rates accompanying the seismicity had a brief excursion from recent trends; other monitoring data streams remained stable. Increased seismicity has diminished but continues; ground deformation rates have stabilized; other monitoring data streams remain stable and show no signs of increased activity. The water lake at the bottom of Halema‘uma‘u continues to slowly expand and deepen. For the most current information on the lake, click here.

Mauna Loa is not erupting and remains at Volcano Alert Level ADVISORY. This alert level does not mean that an eruption is imminent or that progression to eruption from current level of unrest is certain. Mauna Loa updates are issued weekly. 

This past week, about 165 small-magnitude earthquakes were recorded beneath the upper-elevations of Mauna Loa; most of these occurred at depths of less than 8 kilometers (about 5 miles).  Seismicity on the northwest flank increased beginning Dec. 4, including a magnitude-4.1 earthquake and clusters of small, shallow earthquakes occurring closely in time and location. Earthquake swarms in this region have occurred previously in October 2018, April 2017, July 2016, August 2015 and earlier, and do not indicate that an eruption is imminent. Global Positioning System (GPS) measurements show long-term slowly increasing summit inflation, consistent with magma supply to the volcano’s shallow storage system. Gas concentrations and fumarole temperatures as measured at both Sulphur Cone and the summit remain stable. Webcams show no changes to the landscape. For more information on current monitoring of Mauna Loa Volcano, click here.

There were 8 events with 3 or more felt reports in the Hawaiian Islands during the past week: a M3.2 earthquake 10 km (6 mi) SSW of Volcano at 27 km (17 mi) depth on Dec. 8 at 8:55 a.m. HST, M3.2 earthquake 21 km (13 mi) E of Hōnaunau-Nāpōʻopoʻo at -1 km (-1 mi) depth on Dec. 7 at 2:00 p.m. HST, a M1.9 earthquake 5 km (3 mi) NNW of Kukuihaele at 3 km (2 mi) depth on Dec. 6 at 3:07 p.m. HST, a M2.4 earthquake 20 km (12 mi) E of Hōnaunau-Nāpōʻopoʻo at 4 km (3 mi) depth on Dec. 5 at 4:23 a.m. HST, a M3.3 earthquake 21 km (13 mi) E of Hōnaunau-Nāpōʻopoʻo at -1 km (0 mi) depth on Dec. 5 at 3:26 a.m. HST, a M2.3 earthquake 16 km (9 mi) NNE of Pāhala at 9 km (5 mi) depth on Dec. 4 at 8:25 a.m. HST, a M4.1 earthquake 22 km (13 mi) ENE of Hōnaunau-Nāpōʻopoʻo at 4 km (2 mi) depth on Dec. 4 at 7:44 a.m. HST, and a M1.5 earthquake 6 km (3 mi) S of Volcano at 2 km (1 mi) depth on Dec. 4 at 7:43 a.m. HST. 

HVO continues to closely monitor both Kīlauea and Mauna Loa for any signs of increased activity. 

Volcano Watch is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates. 

Photo: The summits of Kīlauea and Mauna Loa are visible in this photo, which looks west.  Kīlauea Caldera, with the collapse area that formed during 2018, is dwarfed by Mauna Loa in the background. Both volcanoes are considered active and will erupt again. USGS photo taken on May 29, 2020.