Kīlauea's recent eruption during the Merrie Monarch Festival, a renowned hula competition, has provided a captivating spectacle and valuable insights into the volcano's behavior. This event, known as Episode 44, showcased the interplay between volcanic activity and cultural celebrations, highlighting the dynamic nature of Hawaii's volcanic landscape.
The eruption began with a series of precursory lava flows from the south vent in Halemaʻumaʻu, a prelude to the main event. What made Episode 44 particularly intriguing was the contrast between the precursory activity and the actual fountaining. While more than 50 precursory lava flows emerged from the south vent, only the north vent erupted lava fountains, reaching a maximum height of about 800 feet. This selective fountaining raises questions about the underlying mechanisms driving volcanic eruptions.
The amount of lava erupted during Episode 44 was significantly lower compared to Episode 43, which could have implications for the volcano's overall activity. The eruption plume, reaching 15,000 feet above sea level, was carried to the north-northeast by southerly winds, with tephra falling on various locations, including Hawaiʻi Volcanoes National Park and Highway 11. The widespread ash and Pele's hair reported as far as Nīnole, about 35 miles away, underscored the impact of the eruption on the surrounding areas.
The response to the eruption was swift and precautionary. The Volcano Alert Level/Aviation Color Code was raised to Warning/Red due to the hazardous conditions on the ground and in the air. Parts of Hawaiʻi Volcanoes National Park and Highway 11 were temporarily closed to ensure public safety. This incident highlights the importance of timely warnings and the dynamic nature of volcanic hazards.
One of the intriguing aspects of Episode 44 was the measurement of volcanic gas emissions. The predominant downwind direction during trade winds made it challenging to measure emissions, as Crater Rim Drive was buried under tephra. However, the southerly kona winds during the episode allowed for the measurement of sulfur dioxide emission rates averaging more than 200,000 tonnes per day, a value comparable to the 2018 lower East Rift Zone eruption. This suggests that past episodes with higher lava output might have had even higher emission rates, adding a layer of complexity to our understanding of volcanic gas dynamics.
As Episode 44 progressed, earthquakes began occurring just south of Halemaʻumaʻu, with 15 shallow earthquakes of magnitude-2 or smaller recorded between 4 p.m. and midnight. The Hawaiian Volcano Observatory staff in the area felt some of these events, indicating their proximity to the surface. This region had been showing sparse small earthquakes during the past few weeks to months, and satellite-based observations revealed upward movement of the south rim of the crater, possibly by as much as 5 inches. The origin of this deformation is not yet clear, and the observatory will continue to monitor this area for further signs.
Episode 44 holds significance in comparing the ongoing episodic eruption at the summit of Kīlauea to previous eruptions. While the Puʻuʻōʻō eruption had 47 episodes before transitioning to effusive lava flows, the ongoing eruption has only 44 episodes from the Puʻuʻōʻō vent alone. This distinction highlights the evolving nature of volcanic activity and the importance of monitoring smaller vents that may not initially exhibit high fountains.
The longevity of the ongoing eruption, with two active vents and impacts on downwind areas, including changing topography, is remarkable. The earthquakes and deformation associated with Episode 44 serve as a reminder that changes are always a possibility on an active volcano. As Kīlauea continues to exhibit episodic eruptions, the Hawaiian Volcano Observatory's close monitoring and timely updates are crucial for understanding and managing volcanic hazards.
Looking ahead, the summit region inflation since the end of Episode 44 suggests the possibility of another fountaining episode, with models indicating a potential start between April 20 and 25. The anticipation of Episode 45, which could be preceded by precursory spatter and/or lava flows from the north and south vents, adds an element of excitement and caution to the ongoing volcanic activity in Hawaii.
