Maunaloa Quakes Elevated Yet Reduced, Kīlauea Still Filling, Am. Samoa

WHAT IS HAPPENING ON MAUNA LOA? Heightened unrest began in mid-September 2022 as recorded by an increase in earthquakes below Mauna Loa summit (from 10-20 per day to 40-50 per day), an increased rate of inflation recorded by GPS stations, and inflation recorded on the MOK tiltmeter. The unrest is likely caused by renewed input of magma into Mauna Loaʻs summit reservoir system. As the reservoir expands it is triggering small earthquakes directly beneath Mokuāʻweoweo caldera and in a region just to the northwest of the caldera. Deeper magma input (greater than 2 miles, 3 km) is detected by the continued increase in upward movement and extension (increase in distance) measured between GPS stations located on the ground surface. Shallower magma input (less than 2 miles, 3 km) was likely responsible for inflation recorded on the summit tiltmeter during the last two weeks of September. The current locations of earthquakes and deformation do not necessarily mean that the next eruption will occur there. Mauna Loa remains at an elevated alert level and aviation color code of ADVISORY/YELLOW. The current increase in activity does not suggest that a progression to an eruption is certain, and there are no indications that an eruption is imminent. DOES THE ADVISORY ALERT LEVEL MEAN THAT MAUNA LOA IS ABOUT TO ERUPT? The ADVISORY Alert level does not mean that an eruption of Mauna Loa is imminent or that progression to an eruption from the current level of unrest is certain. Scientists declared an ADVISORY level for Mauna Loa in July of 2019 because earthquake activity and changes in ground deformation (for example, ground tilt and spreading across the volcano's flanks) are occurring at rates above background levels. At the ADVISORY level, continued increases in earthquake and deformation activity are by no means certain—the level could return to NORMAL without an eruption. Additional information can be found in our fact sheet: U.S. Geological Survey's Alert-Notification System for Volcanic Activity WHY DO HVO SCIENTISTS THINK THAT A MAUNA LOA ERUPTION IS NOT IMMINENT AT THIS TIME? The locations of recent shallow earthquakes are similar to those prior to the 1975 and 1984 Mauna Loa eruptions, but other precursory signals are missing. Signals that have preceded eruptions include upward migration of earthquakes, sustained strong harmonic tremor, accelerated deformation, and overall increase in earthquakes. WILL ERUPTION PRECURSORY SIGNALS BE OBVIOUS IN THE PUBLICLY AVAILABLE MONITORING DATA? Mauna Loa volcano Monitoring in near-real time is available in addition to data in various time frames, which include up-to-date deformation (GPS and tilt) and seismic data plots. The publicly available data has not been processed or reviewed and is made available as a public service. Generally, this data is not sufficient to base public safety decisions on. Many of these signals can only be separated with certainty from other activity on the island by HVO analysts using specialized software and data from multiple stations across the network. The seismic network also picks up signals from wind and weather, blasting in quarries, helicopters and other aircraft, and training exercises at Pōhakuloa Training Area as a few examples of things that might look like increased magmatic/volcanic activity. What do the USGS Volcano Alert Levels and Aviation Color Codes mean? The USGS uses a standardized alert-notification system for characterizing the level of unrest and eruptive activity at U.S. volcanoes for people on the ground and in the air (aviation). The Volcano Alert Levels used by USGS volcano observatories are intended to inform people on the ground about a volcano's status. NORMAL indicates that a volcano is in a background, or non-eruptive state ADVISORY indicates that a volcano is exhibiting signs of unrest above known background levels but does not indicate an eruption is either likely or certain. WATCH indicates a volcano is showing heightened or escalating unrest with increased potential of eruption; it can also mean that an eruption is underway but poses only limited hazards. WARNING indicates a hazardous eruption is imminent, underway, or suspected to be occurring (when visual observations cannot verify an eruption in progress). Aviation Color Codes are used in conjunction with the Volcano Alert Levels to provide information about volcanic-ash hazards in the atmosphere for the aviation sector (for example, airlines, dispatchers, air-traffic controllers, and pilots). Additional information can also be found in our fact sheet: U.S. Geological Survey's Alert-Notification System for Volcanic Activity Under what circumstances will the Volcano Alert Level for Mauna Loa change? USGS scientists will change the Volcano Alert Level for Mauna Loa as warranted based primarily on seismicity (earthquake activity) and ground deformation. Limited monitoring data (primarily from only two eruptions in 1975 and 1984) provides context from which to evaluate Mauna Loa’s status and monitor for any changes occurring. A decrease in earthquake and ground deformation rates may merit Mauna Loa’s Volcano Alert Level being lowered to NORMAL whereas the appearance of eruption precursors (see answer to question above) may merit Mauna Loa’s Volcano Alert Level being raised to WATCH or WARNING. HOW WILL HVO SCIENTISTS RESPOND TO A CHANGE IN THE VOLCANO ALERT LEVEL FOR MAUNA LOA? USGS Hawaiian Volcano Observatory scientists closely track Mauna Loa's seismicity, deformation activity, and gas emissions at the summit caldera through the HVO monitoring network, and they are prepared to deploy additional monitoring instruments on the volcano as needed. These might include additional seismometers, GPS receivers, webcams, and gas-measuring stations. HVO will also continue to provide information about Mauna Loa's status to Hawai‘i County Civil Defense, Hawai‘i Volcanoes National Park, and the public. WHAT CAN I DO TO PREPARE FOR A MAUNA LOA ERUPTION? Preparing for an eruption can help you prepare for other emergencies, such as severe storms and earthquakes, so it's a good thing to do! Learn about the hazards that you might face during an eruption and how to evacuate from your home. Prepare an emergency kit and make a family plan. Know how to get information about the volcano should it become significantly restless or erupt. Agencies that provide information on preparing for natural disasters and other emergencies include Hawai‘i Emergency Management Agency and the American Red Cross. FEMA offers a Ready.gov webpage that provides information specific to preparing for volcanic eruptions. HOW CAN I STAY INFORMED ABOUT THE STATUS OF MAUNA LOA? Subscribe to the Volcano Notification Service and change your settings to receive status updates for Mauna Loa. All current reports are available on HVO website, and past reports can be searched on the Volcano Hazards Program website. HOW WILL I FIND OUT ABOUT A MAUNA LOA ERUPTION? USGS Hawaiian Volcano Observatory scientists closely monitor Mauna Loa around the clock. If an eruption is likely, or is in progress, HVO will immediately notify Hawai‘i County Civil Defense, Hawai‘i Volcanoes National Park, and other emergency managers responsible for public safety. HVO will also issue public notifications through news media, and will post updates and status reports on the HVO website. You can sign up to receive Volcano Activity Notices (updates, status reports, information statements, and alerts) via email for Mauna Loa and other Hawaiian volcanoes by signing up for the free USGS Volcano Notification Service. HVO currently records a Mauna Loa update message that can be accessed by calling (808) 967-8866. This message is a summary of the Mauna Loa Status Report posted on the HVO website. The status report is updated as frequently as the status reports are released, which varies with alert level. HOW MUCH TIME WILL I HAVE TO RESPOND TO A MAUNA LOA ERUPTION? Mauna Loa typically erupts lava at a very high rate, similar to the 2018 eruption of Kīlauea. High eruption rates combined with the steep slopes of Mauna Loa results in fast-moving and long-travelled lava flows, which can require a quick response. How long you have to respond to a Mauna Loa eruption depends on your proximity to the eruptive vent, how steep the slope is between you and the vent, and the rate at which lava is being erupted. If you are in close proximity to, or on a steep (more than 15 degrees) hillside downslope of, an erupting vent on Mauna Loa, you could have precious little time to respond or evacuate—perhaps only hours. The Districts of Ka‘ū and South Kona on the Island of Hawai‘i are at significant risk during a Mauna Loa Southwest Rift Zone (SWRZ) eruption due to the steep slopes and proximity of developed areas relative to the rift zone. During most historic SWRZ eruptions (1868, 1887, 1919, 1950), lava flows reached the ocean in less than a day. In fact, during the 1950 Mauna Loa eruption, one lava flow traveled from the vent at an elevation of about 3,050 m (10,000 ft) to the sea in about 3 hours. On the other hand, the District of Hilo is relatively far from the most active part of Mauna Loa's Northeast Rift Zone (NERZ) and the slopes above the town are fairly gentle. NERZ eruptions can certainly threaten Hilo (for example, the 1855-56 and 1881 lava flows covered land that is now within Hilo city limits), but the lead time for response and potential evacuation during a NERZ eruption is likely to be substantially longer (days to weeks) than for SWRZ eruptions (hours). HOW DOES A TYPICAL MAUNA LOA ERUPTION PROGRESS? All of the previous 33 recorded eruptions on Mauna Loa started within Moku‘āweoweo caldera at the summit of the volcano and we expect future eruptions to follow this pattern. About half of the eruptions remain confined to summit area and did not pose a threat to surrounding communities. However, nearly half of Mauna Loa eruptions have migrated from the summit down either the Southwest Rift Zone toward Hawaiian Ocean View Estates or the Northeast Rift Zone towards Hilo. Rare eruptions can also occur from “radial” vents on the west and north sides below Mauna Loaʻs summit. IS THERE ANYWAY TO KNOW IN ADVANCE IF THE ERUPTION WILL LEAVE THE SUMMIT? Unfortunately not at this time. Records from past eruptions do not provide any clues on how to reliably forecast whether or not a Mauna Loa summit eruption will remain in the summit or move down one of the rift zones. DO PATTERNS OF EARTHQUAKES OR GROUND DEFORMATION PROVIDE CLUES AS TO WHICH RIFT ZONE AN ERUPTION MIGHT OCCUR ON? The pattern of earthquakes and ground deformation prior to an eruption can not reliably be used to determine whether an eruption will move into a rift zone or which rift zone might become active. For example, at the start of the 1984 eruption, activity and earthquakes initially migrated from the summit towards the uppermost part of the Southwest Rift Zone, even producing a short lava flow. But then activity quickly reversed and fissures opened up down the Northeast Rift Zone for the rest of the eruption. CAN MAUNA LOA ERUPTIONS OCCUR ANYWHERE BESIDES THE SUMMIT AND RIFT ZONES? Yes, Mauna Loa can also erupt from radial vents at lower elevations on the north and west flanks. Many older vents of this type predate the arrival of Hawaiians and two have erupted within the past 200 years. The largest occurred in 1859 from a vent not far below the summit on the north flank. Lava flows from this vent took a little over a week to reach the ocean 32 miles away and covering the village of Wainanaliʻi about a mile south of ʻAnaehoʻomalu Bay. The other radial vent eruption occurred on the west flank in 1877 below sea level in Kealakekua Bay and shows the vast reach of these vents. I LIVE IN KAILUA-KONA, CAN MAUNA LOA LAVAS REACH MY HOUSE? No, you live on the slopes of Hualālai volcano which diverts Mauna Loa flows around the area of Kailua-Kona. HOW OFTEN DOES MAUNA LOA ERUPT? Since 1843, Mauna Loa has erupted 33 times, averaging one eruption every 5 years. However, most eruptions occurred prior to 1950, averaging 3.5 years between eruptions. Since 1950, there have only been two eruptions; a summit eruption 25 years later in 1975 and by a rift eruption 9 years later in 1984. As of 2022, it has been 38 years since the last eruption, the longest quiet period on record. WHAT ARE SOME EXAMPLES OF MAUNA LOA ERUPTIONS? All historically recorded Mauna Loa eruptions started in the summit area, and approximately half have stayed in the summit. Seventeen continued from vents in the volcano’s rift zones, producing lava flows that covered broad areas on the lower slopes of the volcano. Seven flows from the Southwest Rift Zone reached the ocean along the west coast of Hawai‘i within a matter of hours. In 1855–56 and 1880–81, lava from Mauna Loa’s Northeast Rift Zone did not reach the ocean but covered land now within the city limits of Hilo. Geologic mapping of Mauna Loa shows that, in the past 150 years, 14 percent (276 square miles) of the volcano’s surface was covered by new lava flows. As much as 35 percent to 40 percent (695 to 795 square miles)—an area equal to or greater than O‘ahu or Maui—was covered in the past 1,000 years. What kinds of volcanic hazards will a Mauna Loa eruption pose? Volcanic hazards associated with a Mauna Loa eruption include: -voluminous, fast-moving lava flows -potentially large and destructive earthquakes and ground motion due to vertical and horizontal movements of the volcano's flanks as it inflates -volcanic gas emissions and dense vog (volcanic smog) that can be a nuisance or potential health hazard to people downwind of the vent -possible explosive eruptions and associated ashfall that can impact air traffic The USGS Fact Sheet, Mauna Loa—History, Hazards, and Risk of Living with the World's Largest Volcano, provides more detailed information about these hazards. A Mauna Loa eruption could disrupt communication, traffic, and people's lives—disruptions that could be further complicated by the influx of large numbers of residents and visitors wanting to see lava flows. These spectators could add to the congestion of roadways and other infrastructure already impacted by the eruption. It's important to note that these impacts will likely be far-reaching. In other words, the impacts will not necessarily be restricted to the immediate area of the eruption or only to the Island of Hawai‘i. For example, during the 1984 Mauna Loa eruption, vog (volcanic smog) blanketed much of the State of Hawaii. --- images and captions by USGS (in order they appear): Image and caption from USGS: Earthquakes beneath Mauna Loa's summit prior to 1975 and 1984 eruptions. Green circles 0-5 km (0-3 mi) deep, red circles 5-10 km (3-10 mi) deep. (Public domain.) Image and caption from USGS: Alert levels and aviation color code icons for volcanoes within the USGS area of responsibility.(Public domain.) Image and caption from USGS: Aerial photograph shows the Ka‘apuna lava flow erupted from Mauna Loa in 1950 as it advanced through the forest at about 3,000 feet elevation on the morning of June 2. This rapidly moving ‘A‘ā lava flow traveled from the Southwest Rift Zone vent to the ocean in about 17 hours. Earlier flows from this same eruption reached the ocean in as little as three hours. (Public domain.) Image and caption from USGS: Lava flows from the 1984 eruption of Mauna Loa loom above the town of Hilo. Photograph taken near the Hilo airport on April 4. (Credit: Little, David. Credit photographer.)