40 Years Ago, Mount St. Helens Blew its Top Off

One day, my Grade Nine science class got way more interesting.

Suddenly, volcanoes weren’t just something in textbooks. Though I was in neighbouring British Columbia when Mt. St. Helens erupted, there was still a layer of ash on our cars and everything else. For a teenager with a burgeoning interest in science, it was awesome.

The Mt. St. Helens eruption was the most violent eruption in US history. It transformed the landscape, filling 62 sq km (24 sq mi) with a debris avalanche. The lateral blast of material damaged 650 sq km (250 sq mi) of land. Nearby river channels were filled with 150 million cubic meters (200 million cubic yards) of volcanic mudflow.

Sadly, 57 people were killed.

Over the 40 intervening years, increasingly high-powered satellites have kept tabs on the area. All those observations have shown scientists a lot about how a landscape recovers from an event of this magnitude.

The leading image is from the Operational Land Imager (OLI) on LandSat 8. It’s from April 17, 2020, and shows how the landscape was transformed by the eruption, and how it still looks after 40 years. Though plant life is slowly reclaiming the area, some areas are stubborn. The leading image is the most recent cloud-free image of Mt. St. Helens from LandSat 8, which can image part of the Earth about every two weeks. There’s still lots of snow, but it’ll be pretty much gone by August.

This side-by-side image compares 1984 with 2013. While much greenery has returned, some areas are stubborn. North of the crater is a pumice plain that is only slowly being reclaimed by plants. The first type to show up was a lupine, a hardy plant native to the area. Legumes like lupines are often first to colonize a difficult environment, because their roots host bacteria that can take nitrogen out of the air and fix it into the soil.

Thanks to satellites, there’s a series of images that shows how the mountain has changed since the eruption. Not only is it a chronicle of plant life reasserting itself, it shows new logging clearcuts reappear, while older ones green in over the decades.

After a volcanic eruption like Mt. St. Helens, reclamation by plant life can be very slow. But it’s fascinating to watch it happen in satellite photos, which are not only plain interesting to see, but of scientific value as well.

Steve Self is a professor at the University of California, Berkeley. He’s a field geologist and a volcanologist. In a press release he said, “I think these long-time series will be useful for decades to come, possibly out to a century after the eruption, as change is very slow.”

Unfortunately, not everyone cherishes the scientific value of the site. Scientists were concerned in 2019 when a Forest Service road was planned through the pumice plain. At the time, there were 33 active research studies taking place on the plain. Scientists say the plain is one of the most unique places on Earth; a 9.6 sq km (6 sq mi) area with almost no trace of human activity. It’s like an untouched laboratory where we can watch nature reassert itself over a landscape.

This GIF animation is from the geostationary satellite GOES-3, or Geostationary Operational Environmental Satellite-3. Geostationary satellite are used to monitor weather over one area, but in this case it proved useful for monitoring an eruption.

The GOES-3 images from that day were also analyzed in research papers published by Self and colleague Rick Holasek. “The Mount St. Helens eruption was possibly the was the first time I saw satellite images from an eruption,” Self said. “I was very interested in these images because they gave a huge overview, and Rick and I had NASA support to explore this “new” technology. That—and the exciting observations we could make—led to our series of papers on the Mount St. Helens eruption clouds.”

The Mt. St. Helens eruption was truly impressive. It sent ash and pumice as far away as Idaho, and the initial cloud from the blast rose quickly: in only four minutes it rose 30 km (18.6 mi).

We’re accustomed to detailed satellite observations of things on Earth now. But when Mt. St. Helens erupted, the technology was not near as advance as now, and satellites weren’t as ubiquitous. There was no such thing as Google Earth.

Now we rely on satellites, and when there’s an eruption, satellite data quickly tells us how the ash might spread, and what air traffic might be affected.

Maybe one day, we’ll even be able to predict eruptions reliably.

More:

• Press Release: Mount St. Helens
• Wikipedia: 1980 eruption of Mount St. Helens
• Universe Today: What Are The Benefits Of Volcanoes?