Mount St. Helens: 30 years later -- what a comeback!
The story of how plants and animals on Mount St. Helens have rebounded after its cataclysmic eruption 30 years ago shows how ecosystems respond to major disturbances.
The cataclysmic eruption of Mount St. Helens 30 years ago today devastated the surrounding landscape, with the hot gas and debris killing countless animals and damaging or destroying large swaths of forest. But life did not entirely end then and there. Among the reasons the ecology rebounded are some surprising factors, including the early morning timing of the eruption, the fact that spring had been late to arrive that year, and the amazing ability of insects to parachute in once a recovery was underway.Skip to next paragraph
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Some species managed to survive amid the the volcano's eruption on May 18, 1980. Others scraped by at the edges of the devastation and literally crawled back. Together they sowed the seeds of a comeback that progressed in fits and starts and continues today.
Ecologists have been watching the process from the very beginning, noting what species were wiped out from the area and which still had a few representatives; which returned to the area and when; and what parts of the damaged landscape were the first to see regrowth.
The recovery of the Mount St. Helens area was "a wonderful living laboratory" to investigate how ecosystems and species respond to and recover from major disturbances, said Charlie Crisafulli, a research ecologist with the Pacific Northwest Research Station in Amboy, Wash.
This natural experiment gave scientists like Crisafulli plenty of surprises and has revealed some important factors that influence how an ecosystem recovers from such widespread devastation, which they have used to study other areas impacted by volcanic eruptions.
One key factor that influenced the recovery of different areas around the volcano was the variety of ways they were impacted by the explosion:
- Nearest the volcano, the explosion completely toppled trees, an area called the blowdown zone that covered about 143 square miles (370 square kilometers). The blowdown zone was also covered in layers of ash of varying depths. Along the fringes of this zone, trees remained standing, but were scorched and killed by the hot volcanic gases and rock fragments that rushed laterally from the explosion. The scorch zone covered about 42 square miles (109 square km).
- The pyroclastic flow raged out of the volcano’s mouth at speeds of up to 125 mph (200 kph) and reached temperatures of up to 1,200 degrees Fahrenheit (650 degrees Celsius). It created a pumice rock plane of about 6 square miles (15.5 square km) just to the north of the volcano. In this barren area where the pumice reached up to 131 feet (40 meters) thick, no remnants of the former forest remained.
- Mudflows, also known as lahars, scoured and buried much of the landscape, killing most of the plant and wildlife in their path, though some survived along the edges of these flows.
- Ash rained down on the landscape for hundreds of miles away from the volcano, carried by the prevailing winds, coating trees and other plants and accumulating in deposits along the ground.
These varying effects created by the explosions established different landscapes in the area that suited some species better than others and set in motion different types of recovery at varying rates.