Lassen Peak, Lassen Volcanic National Park, California

Distance: 5 mi (8 km) round trip
Difficulty: Moderate
Elevation: 8,400 - 10,453 ft (2560 – 3187 m)
Season: late-June to October

Prior to the famous eruption of Mount St. Helens in 1980, the last eruption of a volcano in continental United States occurred on Lassen Peak in Northern California between 1914-1917. Lassen Peak is the southernmost volcano in the Cascade range, although along with its neighbor Mount Shasta, is actually the result of subduction by the tiny Gorda plate, as opposed its larger sister, the Juan de Fuca plate which is responsible for the rest of the Cascade range in Washington and Oregon. Together, they are both remnants of the much larger ancient Farallon plate.

Lassen Peak is also different in nature from most of the other Cascade volcanoes. Rather than being a composite cone of Andesite lava, layers of ash, and cinders, Lassen is a plug dome volcano. This means it is almost entirely composed of extremely thick Andesite lava. However, from its summit, you can actually see examples of all of the other volcano types including a stratovolcano, shield volcano, and cinder cones in the distance.

To get to Lassen Peak, simply visit Lassen Volcanic National Park using the CA-89 highway. The highway takes a route right around the volcano and the trailhead is visible right from the highway on the southside of the mountain.

The trail is pretty self explanatory. From the trailhead, it climbs steeply with relentless switchbacks as you climb the slopes of the volcano. The forest of mountain hemlock grows thinner and shorter as you climb, with whitebark pines becoming more common right near treeline. As the trail climbs above the trees, expansive views of Northern California begin to open up. In the distance, the Sierra Nevada are seen beginning to the south, the Coast range are across the Sacramento valley to the west and the Trinity Alps to the northwest.

As you approach the summit area, the trail levels out and takes you along the rim of the crater that was formed in the 1914-1917 eruption. The one thing you will notice is that rocks along this crater rim are darker and fresher looking than the pale gray of the older rocks. The trail will take you to a weather station next to the true summit.

The summit provides a view down the northern slopes where a pyroclastic flow davastated the area below. In addition, a spectacular view of the 14,000 foot Mount Shasta stratovolcano becomes obvious to the north. The smooth shield volcano of Prospect peak and its associated cinder cones are visible to the northwest. The remnants of an ancient eroded stratovolcano of Mount Tehama are visible south including Pilot Pinnacle, Mount Dillar, and Brokeoff Mountain. The return is a quick 2.5 mile trip down the way you came.