These tiny, crackly bubbles are a new type of volcanic ash
Called bread-crust bubbles, this ash consists of millimeter-long spheres with a crackled surface
LAVA BUBBLES Researchers have discovered a new kind of ash, dubbed bread-crust bubbles, which are tiny spheres of ash no more than a millimeter in diameter that form deep underground.
S. Quane and B. Andrews/Smithsonian Institution