Small breadcrust bomb from Obsidian Dome, CA

Small breadcrust bomb from the 660-year-old eruption of Obsidian Dome, California. It is called a breadcrust bomb because the inside is 'puffed-up' by vesicles (bubbles) and the outside has expanded and cracked, like a loaf of crusty bread. Based on this texture, we can infer that the little bomb erupted at above about 650 C, hot enough for the center to expand. Prepared by Gabi Labishak.