Distribution of Upper Cenozoic Volcanoes and Volcanic Rocks in the Western United States: 10-15 Million Years Ago

Location of active volcanic centers from 10 to 15 million years ago. Black pattern shows volcanic rocks of all compositions. Grid defined by the potentially active volcanic lineaments and loci in the western conterminous United States. The volcanic centers are numbered in the map of active volcanic centers from 0 to 5 million years ago.