We're in the Pacific Northwest this summer. We started in Northern California and are working our way north from there. This area is marked by volcanoes and evidence of past volcanic activity, some ancient, and some not so long ago. This activity has shaped the topography of the region in many ways, and we've found recurring themes in many different places that we've visited.

Our starting point for this journey is Mount Lassen, shown above. Mount Lassen tops out at around 10,500 feet, which means that early in the season, the road through the park isn't open yet. Lassen has bubbling mud pots, much like Yellowstone, which tells us that volcanic activity is still going on not too far below the surface. Mount Lassen last erupted in 1915. Lassen National Park is one of the few places on earth where you can see all four kinds of volcanoes: cinder cone, shield, composite, and lava dome.

One of the neat results of lava flow is "lava tubes." Lava tubes are formed by a very large flow of lava. As the lava begins to cool, the outer edges begin to harden, leaving the center still flowing, as in a tunnel. Picture a lava flow like a huge drinking straw, where the walls of the straw are the cooled and now hardened rock. Except that the straw is 20 or 50 or 100 feet in diameter. When the lava stops erupting, the hot lava in the middle of the lava tube flows out of the tunnel and leaves behind a cavelike structure, much like a subway tunnel. There's one of these near Lassen, and you can explore it on your own, as we did. Just remember that you are completely on your own, and need to bring your own flashlights (and backups), as it's pretty much pitch dark inside.

Here's the entrance to a lava-tube cave.

Here's Jane heading into the unknown. Note that the floor is pretty rough, and there's water to be avoided. Jane is wearing a headlamp, but most of the light for the picture is still from the entrance opening. Once deep into the tunnel, there's not enough light for any pictures.

Here's what it looks like when you come out the other end. It's literally the light at the end of the tunnel.

Heading north from Lassen, we meet Mount Shasta. At 14,180 feet in elevation, Shasta dominates the skyline for miles around.

Mount Shasta last erupted in 1786, and as it typically erupts every 600-800 years, we felt safe enough to camp near its base for a week. Unless you are a mountain climber, there's not a lot to do on Mt. Shasta itself. They say that May is actually a pretty good time to climb it, as the weather is often good. The mountain is always snow covered, so you're in for a long snow and ice climb any time of the year that you ascend it. We drove up to where the trail for the ascent begins, and there was still a lot of snow in the parking lot, and the trail was entirely under snow. There were also lots of cars, indicating that there were a lot of people on the mountain. It can be a dangerous climb, as the accident reports indicate. We didn't go much past the parking lot.

Going north from Shasta, we find Lava Beds National Monument. Remember the subway-like lava-tube cave that we explored near Lassen? Lava Beds has over 700 caves like that, and many are available for exploring on your own. Again, note the phrase "on your own," meaning bring your own lights and find your way out again, on your own.We explored a half dozen or more caves. 

Here I am ready to enter the Golden Dome cave. The bicycle helmet is to protect your head from bumps against the ceiling, and yes, it did prove useful. [Jane's note: I'm pretty sure I would have been both concussed and bleeding if I hadn't been wearing Marie's goofy, purple, childhood helmet. And, hey--which of you kids made off with my grownup bike helmet? Because I look even dorkier than usual in a Barney-purple one.] After entering each cave, we had to wait a few minutes for our transitions-glasses lenses to go clear before we could really see anything. Even then, our flashlights shone for only a limited distance, and we needed to keep our wits about us regarding the path back out, especially in caves with multiple pathways.

Golden Dome cave is named for the yellow/gold plant that grows on its domed ceiling.