Well I wasn't able to get a lot of pictures here due to snow closures. But for those interested in Mt. Lassen here is some Wikipedia information.
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 sulfur 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, an igneous rock, 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 tall volcano sits on the north-east flank of the remains of Mount Tehama, a stratovolcano that was a thousand feet higher than Lassen and 11 to 15 miles 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 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.