Guidance for Volcanic Tephra Fall
Kīlauea volcano has been erupting episodically within the summit caldera since December 23, 2024. Lava fountains have reached up to 1570 feet above the vents, generating eruptive plumes that have risen up to 30,000 feet above ground level in the atmosphere, and carrying volcanic tephra.
Tephra is the word for volcanic materials that travel through the air. From the fountaining episodes, it includes glassy lava fragments, frothy lava called reticulite, and Pele’s hair, which are fine strands of volcanic glass (see images below).
A combination of fountaining dynamics and wind conditions determines where tephra fall may occur for any given eruption episode.
During trade wind conditions, communities to the southwest, in the District of Kaʻū, have been impacted by tephra fall. See the figure to the right that outlines the location of tehphra fall for eruption episodes 1-38, which occurred from 2024 to 2025. The areas impacted by ash fall were more than 30 miles southwest or downwind of Kīlauea.
Epsiode 41, which began on January 24, 2026, was unique in that there were no trade winds and lava fountains reaching 1,475 feet were from both the north and south vents, a rare occurrence. When trade winds are absent, significant tephra fall can occur to the northeast in popular areas of Hawaiʻi Volcanoes National Park and communities surrounding Kīlauea summit, as well as communities farther away in the Districts of Puna and South Hilo.
The figure to the right outlines the area impacted by episode 41 on January 24, 2026. Tephra fall is presented in three size classes; the finest, “ash” (less than 2 mm or 0.08 in.), was distributed widely from Kalapana to north of Hilo.
The left-hand photo shows volcanic ash particles that were collected from a residence in Orchidland, about 33 km (20.5 miles) from the eruption vents. The ash includes blocky particles of volcanic glass, broken pieces of reticulite, and Pele’s hair. These volcanic ash particles are compared to a penny for size (the T in the word ‘TRUST’ is about 1 mm or 0.04 in. tall). The right-hand photo is zoomed in on a broken reticulite particle, showing flat flakes that were bubble walls and pointy triple junctions that look similar to a jacks set played with by kids. Images provided by USGS HVO.
Photo shows tephra on a water tank cover (right) of a home located in Ohia Estates after Kīlauea lava fountaining episode 41 on January 24, 2026.
Tephra fall has raised health concerns from residents and local officials, especially about water catchment systems impacted by tephra. The USGS Hawaiian Volcano Observatory (HVO) is always monitoring data and expects this eruptive pattern, and style will continue for the foreseeable future. Eruption information is available on the HVO website where you can get current updates and notifications. Hawaiian Volcano Observatory | U.S. Geological Survey or https://www.usgs.gov/observatories/hvo
