May 29th, 2012 by

By Michelle Werts

Thirty-two years ago this month, Washington’s Mount St. Helens erupted and collapsed, creating a massive avalanche and a stone- and ash-filled wind that would decimate the surrounding countryside. Nearly 150 square miles of forest were destroyed almost instantly — and then the eruption continued for nine hours. What was once a lush, green landscape was now a barren, gray landscape, but over time the green has slowly returned to Mount St. Helens, as evidenced in this recently released Landsat timelapse from NASA’s Goddard Space Flight Center.

Note: The red in the first few years is how Landsat used to register vegetation.

As shown in this photo taken after the eruption (use the sign as a comparison point between the two photos), Mount St. Helens’ eruption destroyed the old-growth forest.

Mount St. Helens’ eruption destroyed the old-growth forest (use the sign as a comparison point between the two photos). Credit: U.S. Forest Service

In 1979, before the eruption, the ridges north of the volcano were shrouded in old-growth Pacific silver fir and mountain hemlock forests.

In 1979, before the eruption, the area was covered in old-growth Pacific silver fir and mountain hemlock forests. Credit: M. Hemstrom/U.S. Forest Service

Through this video, you can see how vegetation has slowly returned to the Mount St. Helens area while the surrounding areas have been constantly evolving, as well. And for 30 years, scientists have been studying the area around the famous volcano to gather new insight into how areas recover from such catastrophic events. Here are some highlights of what they’ve learned:

  • Legacies can regrow a forest: At the time of the eruption, scientists believed that Mount St. Helens’ ecology would renew the barren landscape with help from species once unknown to the area. Some did, but much of the regrowth can also be attributed to “biological legacies” — the fallen trees, buried seeds and amphibians that survived the blast and have been resilient restarters of the green spaces around the volcano.
  • Thousands of acres of dead trees don’t necessarily equal fire and insect outbreaks: Many advocated for rapid salvage logging of the trees destroyed by the eruption, but in the 110,000-acre Mount St. Helens National Volcanic Monument created in 1982, no such logging was completed — and no massive fire or insect outbreaks occurred. It turns out that volcano ash reduces flammability and repels insects.
  • Native is better: Non-native seeds were spread around Mount St. Helens to help minimize erosion, but it wasn’t very successful. However, natural revegetation was successful in the area, showing that native seeds should always be considered first for erosion control efforts.

While 30 years might seem like a long time and many plants, trees and animals have repopulated this once-ravaged landscape, in ecological terms, recovery has only just begun. It’ll take centuries for the old-growth forest of firs (like Pacific silver and Douglas-fir) and hemlocks to regenerate fully. It’s amazing how one geologic event — a 5.1 Richter-scale earthquake that shook the volcanic mountain, causing the collapse and eruption — can destroy centuries of ecological work. And, it serves as a lesson that once destroyed, nature is not always easy to replace, but the Mount St. Helens area is making a mighty attempt.

Mount St. Helens in 2007

Mount St. Helens in 2007. Credit: Adrien Vieira de Mello (adrivdm)/Flickr