USGS - science for a changing world

Geology of National Parks, 3D and Photographic Tours

Pinnacles National Monument
This view of rhyolite cliffs is near the falls along the Condor Gulch Trail. Rhyolite is a volcanic rock that is similar to granite in composition (mostly quartz and feldspar). Unlike granite, it solidified from rapidly-cooling lava ejected from a volcano. The volcanic rocks in Pinnacles National Park range in composition from rhyolite, dacite, to andesite (silica-rich [felsic] to intermediate mafic rocks [containing some dark iron and magnesium rich minerals]). Rock textures include breccia (rock composed of explosively ejected volcanic rock fagments welded together from the heat of an eruption), flow-banded lava rock (preserving the texture of flowing molten rock before cooling), pumice lapili tuff (welded volcanic ash and sand-sized volcanic debris), and perlite (an opaque form of volcanic glass formed from rapidly cooled lava) (NPS, [2010]).
Next Image Return to Main Page

Accessibility FOIA Privacy Policies and Notices

USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: https://3dparks.wr.usgs.gov/pinn/html/e4.html
Page Contact Information: Education Webmaster
Page Last Modified: 03-May-2017@08:55