Global Volcanism Program | Image GVP-07945
The spectacular giant pumice beds of Primavera volcano represent an unusual sedimentation event following formation of La Primavera caldera. Individual blocks of inflated pumice from 0.3 to >6 m across are enclosed within fine-grained 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 gently settled to the bottom. Subsequent deposition of fine-grained lake sediments buried the pumice blocks.
Photo by Jim Luhr, 1979 (Smithsonian Institution).