MICHAEL MANGA

EPS 214: Physical Volcanology

Lab 4

In this lab you will examine a pumice sample that contains a mixture of white and dark-gray pumice. This sample is from the a deposit near Glass Mountain (Medicine Lake volcano), CA.

Glass Mountain, CA (erupted 900 yrs ago); photo by J. Donnelly-Nolan, USGS

Questions

What is the difference between the dark and light pumice (bubbles, crystals, crytallinity, texture, etc.)?
Why do the bubbles in the light and dark regions look different?
How do you think this type of pumice formed? Is there a relationship to banded obsidian?

Last modified 10 February 2002
Return to Michael's home page