Inclined lava fountains from Kīlauea summit eruption episode 31 on August 22 have blanketed the Halemaʻumaʻu crater floor with tephra, in addition to feeding lava flows extending to the east. USGS photo by M. Zoeller. 

During Kīlauea summit eruption episode 31 on August 22, inclined lava fountains extended 300 meters (1000 feet) laterally from the north vent, going eastward towards the center of Halemaʻumaʻu crater. Inclined lava fountains have been observed before on Kīlauea, in both the Kīlauea Iki (1959) and Maunaulu eruptions (1969) that featured similar episodes of lava fountaining. In both previous cases, the inclined fountains were caused by temporary obstructions within the eruptive vents, usually collapse of part of the vent or surrounding cone. Today’s incline could be caused by construction of an inner cone during the precursory activity before the start of the episode. It’s similar to if you’ve ever put your thumb over a garden hose, causing the water to spray out of the hose at an angle. USGS photo by M. Zoeller.

On August 22, USGS Hawaiian Volcano Observatory scientists hiked to the western rim of Halemaʻumaʻu crater to watch episode 31 of the ongoing Kīlauea summit eruption. Hiking across tephra fields from earlier lava fountaining episodes, renewed eruptive activity was evidenced by a stronger volcanic gas plume as well as heat shimmer above the crater. USGS photo by M. Zoeller. 

Unlike many recent Kīlauea summit eruption episodes, number 31 on August 22 has had a primary lava channel exclusively fed by molten spatter, rather than lava upwelling from the north vent. Other more solid tephra has fallen in a broad plain around the vent. At the top of this frame, the last rays of late afternoon sunlight illuminate the lava fountain above the shadow from Halemaʻumaʻu's crater rim. USGS photo by M. Zoeller. 

Lava fountains at the summit of Kīlauea during episode 31. Afternoon views of the eruption from the northwest caldera rim provided views of the inclined lava fountain from the north vent, as well as the eruption plume. During eruption episodes, sulfur dioxide (SO₂) emission rates increase. According to the National Weather Service, winds are blowing from the northeast at 15-20 miles per hour (8 meters per second), distributing volcanic gas emissions to the south and southwest of the summit caldera. USGS photo by M. Patrick. 

Episode 31 fountains began at 2:04 p.m. HST, after spattering was visible overnight along with several sluggish lava flows from the north vent.  After episode 31 started, lava fountains steadily grew in size to over 325 feet (100 m). The fountains exited the north vent at a 45-degree angle and would be over 500 feet high if they were straight up. USGS photo by M. Patrick. 

With permission from Hawaiʻi Volcanoes National Park, USGS Hawaiian Volcano Observatory staff monitor and document episode 31 of the ongoing eruption at the summit of Kīlauea volcano, which began on August 22. USGS staff use a laser rangefinder to measure the distances lava flows have travelled on Halemaʻumaʻu crater floor, and how and far the lava fountains are extending. USGS photo by M. Patrick. 

As the sun sets on August 22, a lava fountain continues to erupt within Halemaʻumaʻu crater at the summit of Kīlauea. This is the 31rst episode of lava fountaining in Halemaʻumaʻu since this eruption began on December 23, 2024. USGS photo by M. Patrick.