Abstract

Crystals completely or partially enclosed in glass jackets are abundant in the Recent pumice flows and falls that were extruded during the forming of Crater Lake, Oregon, and also are found in the late Oligocene(?) to early Miocene volcanic siltstones of the John Day Formation. Abrasion of the glass and crystals within both the pumice flow and pumice fall portions of the Crater Lake eruption indicates that a considerable amount of solidification, fragmentation, and attrition took place before they reached the atmosphere outside the vent. Bubble-wall texture on crystals within rocks of the John Day Formation suggests a similar origin. Bubble-wall texture of abraded olivine grains from Hawaii indicates the feature may be relatively common in mafic as well as salic-type eruptions.

You do not currently have access to this article.