Page "Geology of the Lassen volcanic area" Paragraph 2

The geology of the Lassen volcanic area presents a record of sedimentation and volcanic activity in the area in and around Lassen Volcanic National Park in Northern California, U. S. The park is located in the southernmost part of the Cascade Mountain Range in the Pacific Northwest region of the United States.

Pacific Oceanic tectonic plates have plunged below the North American Plate in this part of North America for hundreds of millions of years.

Heat from these subducting plates have fed scores of volcanoes in California, Oregon, Washington and British Columbia over at least the past 30 million years ( see Geology of the Pacific Northwest ) and is also responsible for activities in the Lassen volcanic area.