Rhyolite lava flow textures from Long Valley and Yellowstone calderas

Rhyolite lava flow textures from Long Valley and Yellowstone calderas.  A) Photograph of well-developed spherulites in a lava flow from Long Valley Caldera in Eastern California. This high-silica rhyolite flow is very similar to the Central Plateau Member rhyolites of the Yellowstone Plateau Volcanic Field and exhibits many of the same textures. Here, spherulites form from volcanic glass losing gases and causing the very fast crystallization of quartz and feldspar needles that radiate concentrically from a central nucleation point. The largest spherulites in the photo are the size of a hand. B) A flow banded high-silica rhyolite from Yellowstone National Park. Hand lens for scale. Photographs by Lauren Harrison, Colorado State University, taken in May 2024.