Pumice Desert is a barren landscape about 6 miles north of Crater Lake Caldera. The site has a significant deposit of pumice - it is over 100 feet thick. The material fills a pre-existing glacial valley and was delivered via a large pyroclastic flow (ash & pumice flow) during Mazama's 7.7 ka eruption. Pyroclasts include light-colored rhyodacite pumice and darker-colored basaltic andesite scoria.