Lassen Peak is but one of many volcanoes-active, dormant, or extinct-that extend around the Pacific Ocean in a great Ring of Fire. This zone of volcanoes and earthquakes marks the edges of plates that compose the Earth's crust. Volcanic and seismic disturbances occur as these great slabs override or grind past each other.
In May of 1914 Lassen Peak erupted, beginning a seven-year cycle of sporacid volcanic outbursts. The climax of this extended episode took place in 1915, when the peak blew an enormous mushroom cloud some 11 kilometers (7 miles) skyward into the stratosphere. The reawakening of this volcano, which began as a vent on a larger extinct volcano known as Tehama, profoundly altered the surrounding landscape. The area was made a national park in 1916 because of its significance as an active volcanic landscape, with other portions of new park having seen eruptions in 1851. The park is a compact laboratory of volcanic phenomena and most associated thermal features except true geysers. It is part of a vast geographic unit-a great lava plateau with isolated volcanic peaks- that also encompasses Lava Beds National Monument, California, and Crater Lake National Park, Oregon. Before the 1980 eruption of Mount Saint Helens in Washington, Lassen Peak was the most recent volcanic outburst in the contiguous 48 states. The peak is the southernmost volcano in the Cascade Range, which estends from here into Canada. 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 spectacular glaciated canyons and is dotted and threaded by lakes and rushing clear streams. Snowbanks persist year round and beautiful meadows are spread with wildflowers in the spring. The eastern part of the park is a vast lava plateau more than 1.5 kilometers (1 mile) above sea level. Here are found small cinder cones-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 gterminal Geyser. This forested, steep valley also has gorgeous large meadows.
Lassen geothermal areas-Sulphur Works, Bumpass Hell (largest), Little Hot Springs Valley, Boiling Springs Lake, Devils Kitchen and Terminal Geyser- offer fumaroles, boiling mud pots, and waters above 100 degrees celsius (212 degrees fahrenheit). Some of these thermal features are getting hotter. Scientists think that Lassen Park and Mount Shasta are the most likely candidates in the Cascades to join Mount Saint Helens as active volcanoes.