I’ve fallen a bit behind in posting, but I’ll get caught up.
Today’s deskcrop was formed in the violent climactic (ultra?)plinian caldera-forming eruption of Mt. Mazama some 7700 years ago. It is a large pumice ball, with a diameter of almost a foot. I collected it from the forest floor just east of the boundary of Crater Lake National Park. As lightweight as it is, it’s still amazing to me to imagine the power of an eruption that could toss a fragment of rock this size such a distance from the vent. The entire region is covered by a blanket of ash and pumice fragments from this catastrophic eruption – it’s easy to recognize its buff color in roadcuts and borrow pits.