Why Not Visit. . . Lassen Volcanic National Park
Lassen is one of my favorite national parks for two reasons. (1) You can see a lot of the same volcanic features as at other parks (2) without the crowds of other parks. Everyone in the US knows about Yellowstone National Park and its Old Faithful Geyser and Grand Prismatic Spring. Yes, Yellowstone has the world's largest collection of geysers in the world, but it has the crowds to match. When I visited Yellowstone in 2010, I spent more time looking for parking than I did looking at the volcanic features. Watching Old Faithful erupt was a little less magical due to the thousand other people surrounding me on the boardwalk. Lassen has many of these thermal features on a smaller scale, and in all likelihood you can experience them by yourself. Lassen also has something Yellowstone does not. At Lassen I saw excellent examples of the types of volcanoes: cinder cone, shield volcano, and stratovolcano.
I visited Lassen in 2013, when I went on a camping trip with three friends who were also in graduate school for geology. If you can deal with all of the nerding out, I highly recommend visiting a national park with a natural scientist. They will probably notice things other would walk right past. We drove up to Lassen from Santa Cruz, California, which is located about and hour south of San Francisco. The drive from Santa Cruz to Lassen, which is located in Northeastern California at the end of the Sierra Mountain Range, took 4-5 hours. So for those who must fly in to California to visit Lassen, San Francisco International Airport is not a bad option. The high Sierras where Lassen is located get an extreme amount of snow, over 40 ft each winter. Many areas of the park close seasonally until enough snow has melted to allow safe access, this can mean some areas of the park do not open until mid July.
We entered the park from the south and made a pit stop at the south visitor's center. The visitor center is a must see. A three dimensional map equipped with lights in the entrance will show you where the different types of volcanos are located in the park, and a short film will told us about the geologic history of the park as well as show ariel views of different volcanos within the park. Watching that video made the trip for me, because when all of us geologists saw the perfect example of a cinder cone volcano that exists within Lassen on the big screen, we all independently but cohesively decided we wanted to see that cinder cone.