USA 2005 (September 28th) California, Lassen Volcanic National Park

This is a list of lists of active and extinct volcanoes sorted by country. There are separate lists of Antarctic, submarine, and extraterrestrial volcanoes.

A list of volcanoes in United States of America and its territories.

A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from below the surface.

Volcanoes are generally found where tectonic plates are diverging or converging. A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by divergent tectonic plates pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by convergent tectonic plates coming together. By contrast, volcanoes are usually not created where two tectonic plates slide past one another. Volcanoes can also form where there is stretching and thinning of the Earth's crust in the interiors of plates, e.g., in the East African Rift, the Wells Gray-Clearwater volcanic field and the Rio Grande Rift in North America. This type of volcanism falls under the umbrella of "Plate hypothesis" volcanism. Volcanism away from plate boundaries has also been explained as mantle plumes. These so-called "hotspots", for example Hawaii, are postulated to arise from upwelling diapirs with magma from the core-mantle boundary, 3,000 km deep in the Earth.

Lassen Peak, also known as Mount Lassen, is the southernmost active volcano in the Cascade Range. It is part of the Cascade Volcanic Arc which is an arc that stretches from southwestern British Columbia to northern California. Located in the Shasta Cascade region of Northern California, Lassen rises 2,000 ft (600 m) above the surrounding terrain and has a volume of 0.5 cu mi (2 km³), making it one of the largest lava domes on Earth. It was created on the destroyed northeastern flank of now gone Mount Tehama, a stratovolcano that was at least 1,000 ft (300 m) higher than Lassen Peak.

On May 22, 1915, a powerful explosive eruption at Lassen Peak devastated nearby areas, and volcanic ash rained down as far as 200 mi (300 km) to the east. This explosion was the most powerful in a series of eruptions from 1914 through 1917. Lassen Peak and Mount St. Helens – which had a massive eruption in 1980 – are the only two volcanoes in the continental United States to erupt during the 20th century. Lassen Volcanic National Park was created in Shasta County, Calif., to preserve the devastated areas as they were, for future observation and study, and to preserve the nearby volcanic features.

Lassen Volcanic National Park is a United States National Park in northeastern California. The dominant feature of the park is Lassen Peak; the largest plug dome volcano in the world and the southern-most volcano in the Cascade Range. Lassen Volcanic National Park started as two separate national monuments designated by President Theodore Roosevelt in 1907: Cinder Cone National Monument and Lassen Peak National Monument.

The source of heat for volcanism in the Lassen area is subduction off the Northern California coast of the Gorda Plate diving below the North American Plate. The area surrounding Lassen Peak is still active with boiling mud pots, stinking fumaroles, and churning hot springs. Lassen Volcanic National Park is one of the few areas in the world where all four types of volcano can be found (plug dome, shield, cinder cone, and strato).

The park is accessible via State Routes SR 89 and SR 44. SR 89 passes north-south through the park, beginning at SR 36 to the south and ending at SR 44 to the north. SR 89 passes immediately adjacent the base of Lassen Peak.