|6. Volcanic ash
This is an scanning electron
micrograph of a glass shard that came from the cataclysmic eruption
of Mt. Mazama (now Crater Lake, Oregon) ~7,700 years ago. Numerous
vesicles are present in the glass and contribute to low particle
density. The vesicles are also indicative of a highly explosive
eruption of viscous magma. Today, this glass blankets much of the
forested regions of the Pacific Northwest, where it weathers relatively
rapidly to form short-range-order minerals such as allophane, imogolite,
and ferrihydrite. For more information about the eruption of Mt.
Mazama and Crater Lake, click here.