Most fumaroles are complexly zoned in mineralogy and color. The throat of the fumaroles (seen as the vertical whitish lines in the photo) was a place of high acidity and temperatures. High temperatures and acid leached minerals away from these throats. 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/13542825445/">Close up of exposed fumarole pipes on the hingeline northwest of Mt. Cerberus_6_08042013</a>