VHP Photo Glossary: Pahoehoe blister
Pahoehoe blisterBlisters are thin-walled basaltic-glass bubbles formed by the release of volcanic gas from the surface of a pahoehoe flow. Like a glass blower that blows air into molten glass to create a goblet or vase, gas released from lava may force the thin glassy crust of a lava flow to form a large bubble or blister. They are found on all types of pahoehoe flows.
Image: Blister on the surface of a pahoehoe flow, Kilauea Volcano, Hawai`i. Note U.S. quarter for scale.