99 — Ubehebe Crater, located in the northern half of Death Valley, is listed as a moderate threat.
The crater is 140 miles northwest of Las Vegas, Nevada. Its last eruption was about 2,100 years ago.
90 — Mammoth Mountain is a cluster of lava domes posing a moderate threat.
The most recent eruption at Mammoth Mountain occurred about 700 years ago. The mountain has experienced heightened unrest in the past few decades, including earthquakes and volcanic gas emissions.
72 — Coso volcanic field, located in the northern part of the Mojave Desert, also poses a moderate threat.
About 40 eruptions in the past 250,000 years have produced lava domes and hills of volcanic cinder in this field. The most recent eruption occurred about 40,000 year ago.
Small and moderate earthquakes in this area are common, according to the US Geological Survey, and the US Navy monitors geothermal activity in the volcanic field.
69 — The Mono Lake volcanic field, a moderate threat, includes two volcanic islands in a lake and a one volcano on the northwest shore.
Mono Lake's most recent eruption occurred about 300 years ago.
56 — The Salton Buttes, five lava domes in the Imperial Valley of southern California, are a high threat.
The Salton Buttes were omitted from the 2005 threat assessment because researchers were not sure how recent their last eruption was. They now estimate that the eruption occurred 1,800 years ago.
45 — Medicine Lake, located in northeastern California, is a high threat as well.
Medicine Lake has erupted nine times in the past 5,200 years, most recently about 950 years ago.
According to the US Geological Survey, the volcano's center is gradually subsiding. Several shallow earthquakes were reported in this area over the past 30 years.
33 — Clear Lake volcanic field, a high threat, is located in the state's northern Coast Ranges.
The Geysers steam field in the southwest part of this volcanic region provides electricity for 850,000 homes.
About 11,000 years ago, an eruption occurred around Mount Konocti, but there haven't been any more since.
24 — Mono-Inyo Craters, a system of craters and domes such as Obsidian Dome (show below), is a high threat.
This 18-mile chain has not experienced any eruptions in the past 600 years. But the Mono Lake volcanic field, which erupted only 300 years ago, is on the northern tip of Mono-Inyo.
18 — Long Valley Caldera, which is adjacent to Mammoth Mountain in eastern California, was labeled as a very high threat.
The caldera's hot springs are still active, and it helps fuel a power plant that generates power for 40,000 homes.
Long Valley Caldera has not erupted in the past 16,000 years, but it has experienced unrest in the past few years, such as deformation and seismic activity.
11 — Lassen volcanic center, another very high threat, is located in Lassen Volcanic National Park.
More than 50 non-explosive eruptions have been reported in Lassen Volcanic Center over the past 100,000 years, but the area has been mostly quiet for the past 25,000 years.
Three significant eruptions, however, have occurred: the Chaos Crags eruption 1,100 years ago, the Cinder Cone eruption in 1666, and the Lassen Peak eruption just about 100 years ago.
5 — Mount Shasta, the most dangerous volcano in California, is located in the northernmost part of the state.
Mount Shasta formed from the remains of an older volcano that collapsed at least 300,000 years ago. Since then, the volcano has experienced long periods of no activity broken up by short bursts of eruptions.
Scientists have not yet determined when Mount Shasta most recently erupted, but they believe it was 200 to 300 years ago. Earthquake activity in the region has been low in recent years.