Proximal ejecta of the Bolaven extraterrestrial impact, southern Laos

What is it about?

This paper adds to previous evidence that a large crater caused by an extraterrestial impact 789,000 years ago lies beneath a volcanic field in southern Laos. Black, glassy rocks produced by the impact (tektites) and thrown from the crater form the renowned Australasian strewn field. These tektites litter surfaces throughout much of Southeast Asia and beyond and constitute the most extensive known spray of debris produced by an extraterrestrial impact on Earth. In 2020 in PNAS, Kerry Sieh and colleagues first documented evidence that the impact crater is located within the Bolaven volcanic field on the Bolaven Plateau in southern Laos. In this article they add another important piece of evidence that supports that location. They have shown that an unusual and distinctive gravelly, bouldery deposit lies on and surrounding the plateau. The deposit thickens and coarsens toward and is thickest and coarsest on the Bolaven Plateau. The authors argue that the location of the large impact crater under volcanic rocks of the Bolaven Plateau is now all but indisputable.

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Photo by averie woodard on Unsplash

Photo by averie woodard on Unsplash

Why is it important?

For decades, scientists have searched for the source of the most extensive spray of extraterrestrial-impact debris on Earth, the Australasian strewn field. We document a unique pebbly to bouldery breccia that points unambiguously to its source—an impact crater buried beneath lavas of the Bolaven Plateau in southern Laos. The crater’s location is constrained by the breccia’s thickening and coarsening onto the plateau. The stratigraphic details of this extensive and well-preserved deposit reveal important details about the processes involved in creation of the crater and its ejecta.