Hiking Lassen Peak in the summer and fall is very rewarding. The incredible views of Northern California that include Lassen Volcanic National Park, Mount Shasta and the Trinity Alps is well worth the ascent. This hike is also perfect during a full moon, as the trail has been recently renovated and is easy to see.
Lassen Peak is the world's largest plug dome volcano and the southernmost active volcano in the Cascade Mountain Range. This volcano was formed from redirected lava flow after a larger nearby volcano (known as Mount Tehama) went extinct around 400,000 years ago. From 1914 through 1917 Lassen Peak underwent its own series of eruptions. The largest eruption occurred on May 22, 1915, and sent ash over 200 miles to the east. This same eruption created the “Devastated Area” seen running down from the peak to the northeast. Since 1917 the only other volcano in the Cascade Range to erupt has been Mount St. Helens.
Lassen Peak is primarily composed of dacite rock that started flowing from the northeast edge of Mount Tehama around 31,000 years ago. As this lava cooled it created the talus slopes of Lassen Peak. At only 100 years old, the black dacite atop the peak is the youngest rock in California. This rock was formed during the May 22, 1915, eruption.
A special animal is found on the slopes of Lassen Peak: the American pika (Ochotona princeps) is a small mammal that helps scientists study climate change. Habitat for the American pika has been shrinking as the climate warms, and they have been driven further and further up the mountain in search of cooler temperatures. Scientists and members of the National Park Service are monitoring the American pika and its habitat range in a three-year research project titled “Pikas in Peril.”