Accretionary Lapilli

Lapilli found on the flank of the Darwin Volcano in the Galapagos Islands. Image Credit: David K. Lynch (from Earth Science Picture of the Day)

Pellets that form by accretion of fine ash around condensing water droplets or solid particles; particularly common in steam-rich volcanic eruptive columns, but also occurring in the turbulent explosion plume rising above an expanding excavation cavity in an impact cratering event. Accretionary lapilli exhibiting concentric internal structure have been found in deposits at the Ries impact structure and in ejecta deposits from the Chicxulub crater in Mexico.

The meteorite NWA 7034 and its pairings include what some scientists are calling accretionary lapilli and others call “blueberries.”


Some or all content above used with permission from J. H. Wittke.