EPS 214: Physical Volcanology

Lab 5

In labs 1, 2 and 4 you tried to make sense of banded volcanic rocks. What did you learn?

Bands exist at all scales. The goal of this lab is to use different techniques to characterize the banded structure of obsidian and to develop a framework in which these bands can be interpreted. Our field trip will then focus on collecting the information we need to interpret bands in a quantitative way.

The questions I am hoping we can address are 1) what type of flow and how much strain did the magma accumulate? 2) how much mingling occured in a magma chamber? 3) what insight can we obtain about chamber dynamics and structure? 4) How does obsidian form? These are all challenging questions. Keep these in mind as we think about how to measure properties of the bands and how to interpret the bands.

As part of this lab we will look at thin sections from the coarse vesicular pumice (CVP) from the Little Glass Mountain, CA obsidian flow. Using everything you have learned try to answer the question: When did these bubbles form?

Medicince Lake, CA (shield volcano, and location of Little Glass Mountain); photo by J. Donnelly-Nolan, USGS

Last modified 10 February 2002
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