“Lassen Volcanic National Park is one of the lesser-known and less visited of the national parks in California. Many have heard of Lassen Peak, but the park is located in the northern reaches of the state relatively far from most population centers. It's a fascinating place, and if one is interested in volcanism, there are examples of practically every type of volcanic feature within the borders of the park. How many places in the world have shields, lava plateaus, stratovolcanoes, plug domes, cinder cones, and calderas, as well as active geothermal fields (fumaroles, boiling mudpots, and hot springs; everything except geysers, so Yellowstone can rest easy). The park is also noted for the recency of many of these features, with numerous cones and flows that are less than a few thousand years old (Lassen itself erupted from 1914-1917).”
"Lassen Peak is an odd one. Most people have a stereotypical view of what a volcano "should" look like, and to most people, Lassen doesn't fit the stereotype. Yes, it is an isolated peak from most angles, but where is the cone shape, and where is the crater on top? "
"Mt. Tehama, or the Brokeoff Volcano, began erupting around 600,000 years ago just south of the present-day site of Lassen Peak. It was a stratovolcano similar to Mt. Shasta or Mt. Hood, composed mainly of gray andesite with interbedded ash and lava flows. The mountain alternated between explosive eruptions and effusive eruptions and eventually grew to a height in excess of 11,000 feet, hundreds of feet higher than modern Lassen Peak (10,457 feet)."