Lassen Volcanic National Park - General Park Information

To visit Lassen Volcanic National Park is to witness a brief moment in the ancient battle between the earth shaping forces of creation and destruction in Northern California. Nestled within Lassen's peaceful forests and untouched wilderness, hissing fumaroles and boiling mud pots still shape and change the land, evidence of Lassen's long fiery and active past.

On May 22, 1915, an explosive eruption at Lassen Peak, the southernmost active volcano in the Cascade Range, devastated nearby areas and rained volcanic ash as far away as 200 miles to the east. This explosion was the most powerful in a 1914-17 series of eruptions that were the most recent to occur in the Cascades prior to the 1980 eruption of Mt. St. Helens. Lassen Peak is the largest of a group of more than 30 volcanic domes erupted over the past 300,000 years in Lassen Volcanic National Park.

Because geologically recent volcanic activity in an area is the best guide to forecasting future eruptions, scientists study the lava flows, ash, and other deposits from past eruptions. Volcanoes in the Lassen area tend to erupt infrequently, and may be inactive for periods lasting centuries or even millennia. The most recent eruptions in the Lassen area were the relatively small events that The Chaos Crags, a group of six lava domes, was formed about 1,100 years ago in the latest large eruptions to occur in the area of occurred at Lassen Peak between 1914 and 1917. The most recent large eruption produced Chaos Crags about 1,100 years ago. Such large eruptions in the Lassen area have an average recurrence interval of about 10,000 years. However, the geologic history of the Lassen area indicates that volcanism there is episodic, having periods of relatively frequent eruptions separated by long quiet intervals. For example, the last large event before the Chaos Crags eruption was the one that built Lassen Peak 27,000 years ago.

Hydrothermal (hot water) features at Lassen Volcanic fascinate visitors to this region of northeastern California. Boiling mud pots, steaming ground, roaring fumaroles, and sulfurous gases are linked to active volcanism and are all reminders of the ongoing potential for eruptions in the Lassen area. Nowhere else in the Cascade Range of volcanoes can such an array of hydrothermal features be seen.

Weather plays a dramatic role at Lassen Volcanic National Park. Winter, especially, shapes the landscape; snow generally begins to accumulate each year in October, doesn't melt in most places until July, and can remain in isolated areas year round. Summer weather is more predictable, with warm, dry days, blue skies, and cool nights. Visitors to Lassen Volcanic National Park should be prepared for any kind of weather, any time of the year.