After leaving the Ape Caves, we had one more day before we had to head back east, so we hit up the Johnston Ridge Observatory for a close up view of Mount St. Helens. From there, you have a very clear view of the eruption site, the crater, and the lava dome that began forming in the crater after the eruption. The observatory is actively used for scientific monitoring of the volcano, but it also serves as a museum, movie theater, and trail head for many hikes. It’s the first National Volcanic Monument we’ve visited, and I am treating it like a national park. On our trip, we went to the Johnston Observatory and hiked the Boundary Trail through the area cleared by the 1980 eruption.
Surprisingly to me, volcanologists aren’t very good at predicting eruptions. I knew this was true for earthquakes, thanks mostly to Nate Silver, and the same complex rationale holds here. So, in 1980, when the mountain started smoking and quaking, scientists knew it would likely erupt, but they expected something small and gentle. As most people probably know, the actual eruption was anything but. An earthquake set off a huge landslide that removed a significant chunk of the top of the mountain. The landslide was immediately followed by a giant explosion of steam, gas, rock and lava. The combination devastated the surrounding area, killing 57 people and causing over a billion dollars in economic damage. I won’t try to explain the science, but as usual, Wikipedia does a pretty good job.
The Observatory was built after the eruption to study the volcano. It was named after volcanologist David Johnston, who was killed in the blast. At the Visitor’s Center, you can see two movies about the 1980 eruption, one focused on geology and one on biology. We enjoyed the 20 minute biology movie. There are also a few small exhibits about the eruption, stories from survivors, damage to the surrounding area, and even a seismograph hooked to the floor for measuring your own earthquake.
National Park Passes are good here so you don’t have to pay the $8 per person fee. The visitor center and movies are free with the entrance fee.
One especially fun fact we learned is that volcanologists predict Mount Hood, where we had just spent three days, is likely the next to blow. Good to know!
From the observatory, we took the Boundary Trail out to get a closer look at the mountain and at Spirit Lake. When the volcano erupted, all the water in the lake was displaced about 800 feet up the hillside, and raising the lake bed by 200 feet. The lake is still full of fallen, dead trees today. We hiked out a mile or two, took some pictures, and headed back down the mountain to find a campsite for the night. You can get permits for backpacking and even to climb reasonably close to the crater, but we skipped the backpacking this time around. It looked hot and dusty, maybe we’ll give it a shot next time we’re in the area during cooler weather.