Three distinct magma erupted from the Novarupta vent. The banding in this piece of pumice show two of them. NPS photo by M. Fitz.
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/99350217@N03">Katmai National Park and Preserve</a>
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/katmainps/13542840623/">Dacite and andesite banded pumice, I think</a>