The September eruption of the Kilauea Volcano on the Big Island of Hawaii has been declared over by the Hawaii Volcano Observatory (HVO) unit of USGS. With the eruption over, the amount of volcanic gas spewing into the air has also been significantly reducing, helping clear the air of many communities on the island which had harmful levels of volcanic-induced air pollution.
On September 10, Kilauea exploded to life after an intense swarm of earthquakes near the summit. The lava put on quite the show for visitors who were able to safely observe the eruption inside the volcano caldera from above it at Hawaii Volcanoes National Park. The lava never left the summit caldera and USGS says the eruption, which ended on September 16, is unlikely to re-start anytime soon. HVO also says that there’s been no unusual activity observed elsewhere along Kilauea’s East Rift Zone or Southwest Rift Zone.
“Eruption of lava from the fissure vents on the downdropped block of Kilauea’s summit caldera stopped on September 16, and there was no observable activity anywhere at the summit yesterday or this morning. Overnight webcam views showed no incandescence across the eruption area and an overflight confirmed the lack of activity. We do not expect the eruption to resume based on the behavior of past, short-lived summit fissure eruptions (1982, 1975, 1974, 1971),” HVO wrote in an update shared this morning.
HVO adds, “Sulfur dioxide (SO2) emissions have also decreased to near background levels based upon the very weak plume visible this morning. Sulfur dioxide levels were measured at a rate of 200 tonnes per day yesterday, September 17. This value is down dramatically from the 190,000 tonnes per day measured just after the onset of the eruption on Sunday, September 10th, and is typical of non-eruptive periods.”
These volcanic emissions create hazy air pollution known as “vog”. Vog consists primarily of water vapor, carbon dioxide, and sulfur dioxide. As the sulfur dioxide gas mixes with UV light from the sun, oxygen, moisture, and other matter in the atmosphere, it converts to fine particles that scatter sunlight, causing a visible haze.
The significant volcanic gas emissions were very noticeable in Hawaii in the days after the eruption, especially on the west coast of the island where winds helped carry bring the volcanic emissions to, but relaxed to leave them there. Purple Air sensors on the island showed high air pollution levels, but with the eruption now over, the levels have returned to a cleaner normal.
Sulfur dioxide affects human health when it is breathed in. It irritates the nose, throat, and airways to cause coughing, wheezing, shortness of breath, or a tight feeling around the chest. The effects of sulfur dioxide are felt very quickly and most people would feel the worst symptoms in 10 or 15 minutes after breathing it in. Those most at risk of developing problems if they are exposed to sulfur dioxide are people with asthma or similar conditions. Extreme concentrations of sulfur dioxide can be deadly if inhaled. When combined with other substances additional hazards can be created; as an example, rain falling through a sulfur dioxide plume could produce an acid rainfall. Sulfur dioxide is invisible to the human eye, but when it reacts with other gases, aerosol particles can form to cause haze, and according to NASA in extreme widespread events, climate cooling.
During the May 2018 eruption of Hawaii’s Kilauea Volcano’s Lower East Rift Zone, sulfur dioxide was covering the surface in a residential neighborhood from erupting fissures. During that eruption, a plume of sulfur dioxide was detected by the Ozone Mapper Profiler Suite (OMPS) on the Suomi-NPP satellite. During the height of that eruption during the spring and summer of 2018, authorities evacuated people from the danger sulfur dioxide posed. “Hawaii Fire Department reports extremely dangerous conditions due to high levels of Sulfur Dioxide gas in the evacuation area. Elderly, young, and people with compromised respiratory systems are especially vulnerable,” warned the Hawaii County Civil Defense in 2018. They added, “The high levels detected are an immediate threat to life for all who become exposed. First responders may not be able to come to the aid of residents who refuse to evacuate. ”
But with the location of the eruption contained to the caldera for this event and wind patterns steering pollutants around the south side of the island to the west side, there wasn’t that same harmful concentration that was seen in 2018.
Volcanoes also release other harmful substances into the air. The Keanakākoʻi Viewing Area inside Hawaii Volcanoes National Park was closed due to high concentrations of sulfur dioxide (SO2) and other volcanic particulates. On September 11, the National Park Service said that the plume of gas rising from the fresh eruption also contained other gases and shards of volcanic glass that “pose a significant risk to anyone.”
With the eruption over, that part of the park has since re-opened to visitors to peer down into the cooling, black lava inside the caldera of Kilauea.
With the volcanic activity wrapped up for now, HVO also dropped the Volcano Alert Level down to “ADVISORY” and the Aviation Color Code down to “YELLOW.” This change happened Sunday morning.
AVO is responsible for issuing Aviation Codes and Volcanic Activity Alert Levels. Aviation Codes are green, yellow, orange, or red. When ground-based instrumentation is insufficient to establish that a volcano is at a typical background level of activity, it is simply “unassigned.” While green means typical activity associated with a non-eruptive state, yellow means a volcano is exhibiting signs of elevated unrest above known background levels. When a volcano exhibits heightened or escalating unrest with the increased potential of eruption, it jumps to orange. Finally, when an eruption is imminent with significant emission of volcanic ash expected in the atmosphere or an eruption is underway with significant emission of volcanic ash into the atmosphere, the code becomes red. Volcanic Activity Alert levels are normal, advisory, watch, or warning. As with aviation codes, if data is insufficient, it is simply labeled as “unassigned.” When the volcano is at typical background activity in a non-eruptive state, it is considered normal. If the volcano exhibits signs of elevated unrest above background level, an advisory is issued. If a volcano exhibits heightened or escalating unrest, a watch is issued while a warning is issued when a hazardous eruption is imminent.