Avalanche of change

Mount St. Helens 20 years after the eruption

When Mount St. Helens erupted in 1980, it set off an enormous avalanche, spewed out deadly hot steam, and buried a vast area with volcanic rock and ash, violently shattering its 123-year ’slumber.’ Ecologists used this once in a life-time chance to discover how ecosystems respond to such a natural disturbance.

The symposium “Ecological Recovery After the 1980 Eruptions of Mount St. Helens” will reveal how the surrounding landscape, including forests, soils, steams, lakes, fish, amphibians, birds, and mammals have fared in the ensuing two decades.

“The eruption highlights the importance of factors such as chance events, life history characteristics, and timing and confirms the surprising resilience of nature,” says symposia organizer Virginia Dale (Oak Ridge National Laboratory).

Dale will kick off the session with her presentation “Is succession successful? Synthesis and management implications of ecological recovery at Mount St. Helens.” She will provide an overview of survival, colonization, and community development among the six disturbance zones the eruption generated: pyroclastic flows, debris avalanche, mudflows, blown-down trees, scorched vegetation, and ash deposition.

Frederick Swanson (US Forest Service, Pacific Northwest Research Station) will focus on the most intense aspects of the eruption, such as landslides and 800 degree Celsius heat of pyroclastic flows and the ways in which they altered the landscape. His talk “Geological and ecological settings of Mount St. Helens before and after May 18, 1980” will describe the link between the reshaped geophysical landscape and the plants and animals living on it.

The session will also delve under the surface in “Life in the changing belowground during succession on Mount St. Helens,” which will be presented by Michael Allen (University of California-Riverside). Allen will highlight the dynamic interactions between plants, fungi, and animals as they collectively drive the changes occurring on this disturbed landscape.

Other speakers in the session will address the status of plants in the area’s old growth forests as well as the roles of insects, mammals, and birds in reconstructing the environment post-eruption.

The dramatic transformation of Spirit Lake as well as the eruption’s consequences on fish and amphibians will be addressed by Charlie Crisafulli (US Forest Service, Pacific Northwest Research Station). Among his findings: river fishes, that originally suffered high mortality have rebounded remarkably in many cases and several amphibians species have colonized new ponds that the blast created.