Witness the raw power of nature as a new volcanic cone, or puʻu, takes shape on Kīlauea! This week, we delve into how scientists at the U.S. Geological Survey Hawaiian Volcano Observatory (HVO) are meticulously tracking the growth of this new feature. It's a fascinating look at the dynamic forces that constantly reshape our planet. This article is written by HVO geologist Natalia Deligne.
First, let's understand the basics: Tephra – that's the scientific term for the rock fragments ejected during an eruption, including the famous Pele's hair. As tephra rained down on a closed section of Crater Rim Drive, HVO geologists began their monitoring efforts. Initially, they used a simple method: photographing a road sign as it was progressively buried. It was a clear and easy method to track the growth of the puʻu, but it was quickly overwhelmed. By the end of episode 21 of the eruption, only an inch or two of the sign was still visible!
Next, the team tried a more structured approach, setting up garden stakes at regular intervals to measure tephra accumulation, much like a rain gauge. However, the puʻu's rapid growth during lava fountaining episodes quickly rendered this method ineffective. Episode 23 buried five of the 12 stakes, and episode 24 buried three more.
But here's where it gets interesting... Faced with these challenges, HVO scientists turned to higher-tech solutions. They started using hand-held, high-precision GPS instruments to walk transects, carefully measuring the elevation changes. GPS measurements are taken at several locations, including the closest stable location near the peak of the puʻu (the exact location of the peak changes between episodes, and slumping/cracking near the peak can make the very top unsafe). The instrument needs to 'see' enough satellites (typically between 10 and 20) to ensure a vertical accuracy of 30 centimeters (about 1 foot). This process takes several seconds to several minutes. Then, a location is recorded every second for 4 minutes (240 seconds). The entire process takes 2-3 hours to complete. Back in the lab, the data is corrected using a permanent GPS monitoring station nearby, resulting in final averaged locations with a vertical accuracy of around 10 centimeters (about 4 inches). This data allows scientists to track the puʻu's growth over time. They also use high-precision elevation data collected using lidar (light detection and ranging) in 2019.
HVO also employs an airborne lidar system mounted on a helicopter, providing high-resolution, three-dimensional scans of the entire puʻu. Although this is done roughly once a month, processing the data is complex and ongoing. Attempts to use photogrammetry, a method used to track elevation changes across the crater floor, have been unsuccessful due to the new puʻu's uniform surface lacking distinct features.
The data paints a clear picture of the puʻu's rapid growth during lava fountaining episodes. For instance, at the location of the now-buried road sign, the tephra deposit reached a thickness of 3.4 meters (about 11 feet) by May 31, 2025, after episode 23. During episode 24, over approximately 7.5 hours, an additional 7.8 meters (about 25.6 feet) of tephra accumulated. And in just 5 hours, episode 36 added another 7.5 meters (about 24.6 feet)!
This growth is most pronounced during high-fountaining episodes, where lava fountains can exceed 300 meters (about 1,000 feet) in height. When lava fountains are lower, it's more difficult for tephra to escape Halemaʻumaʻu and contribute to the puʻu's formation. It's a reminder of how quickly the landscape can change, with the new puʻu rising where visitors once drove around Halemaʻumaʻu. HVO geologists will continue to monitor this evolving feature, providing valuable insights into the dynamic nature of Hawaiian volcanoes.
Volcano Activity Updates
Kīlauea has been experiencing episodic eruptions within its summit caldera since December 23, 2024. The USGS Volcano Alert level is WATCH.
Episode 37 featured lava fountaining for 9 hours on November 25. The summit is reinflating, with intermittent overnight glow visible at both vents. Another fountaining episode is expected between December 6 and 9. No unusual activity has been observed along Kīlauea’s East Rift Zone or Southwest Rift Zone.
Mauna Loa is currently not erupting, and its USGS Volcano Alert Level is NORMAL.
One earthquake was felt in the Hawaiian Islands last week: a M3.5 earthquake, 1 km (0 mi) west of Pāhala, at a depth of 32 km (20 mi) on November 29 at 6:39 p.m. HST.
HVO continues to closely monitor both Kīlauea and Mauna Loa.
For more information, including past Volcano Watch articles, Kīlauea and Mauna Loa updates, photos, maps, and earthquake information, visit HVO’s website. You can also email questions to askHVO@usgs.gov.
What do you think? Does this rapid transformation of the landscape surprise you? Are there other methods you'd suggest for tracking volcanic activity? Share your thoughts in the comments below!
