| The Pine Creek volcanic assemblage consists of the deposits of hot pyroclastic flows and lahars that are interbedded with alluvium. The assemblage was formed during two or more postglacial episodes of explosive andesitic and dacitic volcanism at an old Mount St. Helens volcano which coincided with, but predated, the modern cone. ... Radiocarbon dates indicate that the oldest Pine Creek eruptive episode occurred before about 12,000 years ago and the youngest between 3,000 and about 2,500 years ago. -- Crandell and Mullineaux, 1973 |
