Global Volcanism Program | Image GVP-07945
The giant pumice beds at Primavera volcano represent an unusual sedimentation event following formation of La Primavera caldera. Individual pumice blocks from 0.3 to more than 6 m across are enclosed within fine-grained volcanic ash-rich lake sediments. The giant pumice blocks originated by eruption of rhyolitic lava into a caldera lake. The pumice fractured into large blocks that floated to the surface, rafted across the lake, and settled to the bottom after becoming waterlogged. Subsequent deposition of fine-grained lake sediments buried the pumice blocks.
Photo by Jim Luhr, 1979 (Smithsonian Institution).
This image is made available under the Public Domain Dedication CC0 license, but proper attribution is appreciated.