Lassen Volcanic National Park - Geography and Climate

Geography and Climate

The park is located near the northern end of the Sacramento Valley. The western part of the park features great lava pinnacles (huge mountains created by lava flows), jagged craters, and steaming sulphur vents. It is cut by glaciated canyons and is dotted and threaded by lakes and rushing clear streams.

The eastern part of the park is a vast lava plateau more than one mile (1.6 km) above sea level. Here, small cinder cones are found. (Fairfield Peak, Hat Mountain, and Crater Butte). Forested with pine and fir, this area is studded with small lakes, but it boasts few streams. Warner Valley, marking the southern edge of the Lassen Plateau, features hot spring areas (Boiling Springs Lake, Devils Kitchen, and Terminal Geyser). This forested, steep valley also has large meadows that have wildflowers in spring.

Lassen Peak is made of dacite, and is one of the world's largest plug dome volcanoes. It is also the southernmost non-extinct volcano of the Cascade Range (specifically, the Shasta Cascade part of the range). 10,457-foot (3,187 m) tall volcano sits on the north-east flank of the remains of Mount Tehama, a stratovolcano that was a thousand feet (305 m) higher than Lassen and 11 to 15 miles (18 to 24 km) wide at its base. After emptying its throat and partially doing the same to its magma chamber in a series of eruptions, Tehama either collapsed into itself and formed a two-mile (3.2 km) wide caldera in the late Pleistocene or was simply eroded away with the help of acidic vapors that loosened and broke the rock, which was later carried away by glaciers.

On the other side of the present caldera is Brokeoff Mountain (9,235 feet or 2,815 m), which is an erosional remnant of Mount Tehama and the second highest peak in the park. Mount Conrad, Mount Diller, and Pilot Pinnacle are also remnant peaks around the caldera.

Sulphur Works is a geothermal area in between Lassen Peak and Brokeoff Mountain that is thought to mark an area near the center of Tehama's now-gone cone. Other geothermal areas in the caldera are Little Hot Springs Valley, Diamond Point (an old lava conduit), and Bumpass Hell (see Geothermal areas in Lassen Volcanic National Park).

The magma that fuels the volcanoes in the park is derived from subduction off the coast of Northern California.

Cinder Cone and the Fantastic Lava Beds, located about 10 miles (16 km) northeast of Lassen Peak, is a cinder cone volcano and associated lava flow field that last erupted about 1650. It created a series of basaltic andesite to andesite lava flows known as the Fantastic Lava Beds.

There are four shield volcanoes in the park; Mount Harkness (southwest corner of the park), Red Mountain (at south-central boundary), Prospect Peak (in northeast corner), and Raker Peak (north of Lassen Peak). All of these volcanoes are 7,000-8,400 feet (2,133-2,560 m) above sea level and each is topped by a cinder cone volcano.

During ice ages, glaciers have modified and helped to erode the older volcanoes in the park. The center of snow accumulation and therefore ice radiation was Lassen Peak, Red Mountain, and Raker Peak. These volcanoes thus show more glacial scarring than other volcanoes in the park.

Despite not having any glaciers currently, Lassen Peak does have 14 permanent snowfields.

Since the entire park is located at medium to high elevations, the park generally has cool-cold winters and warm summers below 7,500 feet (2,300 m). Above this elevation, the climate is harsh and cold, with cool summer temperatures. Precipitation within the park is high to very high due to a lack of a rain shadow from the Coast Ranges. The park gets more precipitation than anywhere else in the Cascades south of the Three Sisters. Snowfall at the new visitor center near the southwest entrance at 6,700 feet (2,040 m) is around 430 inches (1,100 cm) despite facing east. Up around Lake Helen, at 8,200 feet (2,500 m) the snowfall is around 600–700 inches (1,500–1,800 cm), making it probably the snowiest place in California. In addition, Lake Helen gets more average snow accumulation than any other recording station located near a volcano in the Cascade range, with a maximum of 178 inches (450 cm). Snowbanks persist year-round.