From a Mountain of Fire to a Mosaic of Life
By Ryan Brady, Chemical Engineering & Biochemistry, 2022
As the sun rose on May 18, 1980 in Skamania County, Washington, all appeared to be normal; however, this would all change rapidly. At 8:32 AM, an earthquake caused a massive landslide leading to the eruption of Mount St. Helens. The eruption sent lava and rock down the northern face of the volcano, destroying everything in its path. It also triggered the release of a hot gaseous cloud, instantly searing everything it touched. The finale of the eruption was the massive plume of ash that shot into the sky and coated the surrounding area. Fifty-seven people died from the eruption, and it caused $1.1 billion in damages. Beyond the economic and human impact, the environmental impact was unprecedented. Virtually everything that came in contact with the eruption was annihilated. Over time, however, the environment has been rebuilding, first with grasses and small bushes and eventually blooming back into a luscious forest. This process of recovery is known as succession.
Succession is the ecological process in which ecosystems change over time. The process can take anywhere from decades to millions of years. After most disruptions, one of two types of succession occur: primary or secondary. In primary succession no soil is present, such as in the areas of newly formed rock. Secondary succession occurs when the soil remains intact and is a significantly faster process. This is the type of succession that would occur after an event such as a forest fire.
With an event as traumatic and multifaceted as the eruption of Mt. Saint Helens, the succession is a very complex and nonlinear process.
With an event as traumatic and multifaceted as the eruption of Mt. Saint Helens, the process of succession is a very complex and nonlinear one. Because areas were impacted unequally by the eruption, different areas have recovered at different rates. The nearby lake, Spirit Lake, has recovered the fastest but may never fully return to its original state. The lake was initially a deep lake that was pristine as a result of the runoff from the mountain; however, when the eruption occurred, the flow ended up in the bottom in the lake — creating a warm, shallow, and oxygen-deprived environment. Initially, a small number of anaerobic bacteria began growing in the lake. Over time, the debris has cleared from the surface, increasing the light transmittance and allowing the redevelopment of plant and animal species. Additionally, the illegal introduction of rainbow trout in 1993 served as an interesting ecological event, as the fish have exhibited shorter life cycles but grow larger. Scientists attribute this to denser vegetation that has developed without any natural predators, which allow the trout’s prey to thrive.
One of the most unique aspects of the volcanic eruption was how some species were able to survive and repopulate quickly while others were completely wiped out. These successful species are known as “biological legacies.” Among the first organisms to reemerge were fungi. Certain species of fungi have adapted to grow after forest fires but had responded in a similar manner to the eruption. Because of the relatively small area of impact of the disruption in comparison to a forest fire or similar disturbance, many early plant colonizers were blown into the area from the surrounding forest. The first animals that emerged were mice and moles. The moles served a unique role because their burrowing mixed the soil and the volcanic ash making it much more hospitable for new plant growth. More recently, trees that were present before the eruption have begun regrowing in the area. Currently, the canopy ranges from 15 to 25 feet tall — composed of mountain hemlocks and Pacific silver firs. Despite this progress, the area is still decades away from resembling the pre-eruption ecosystem.
The most intriguing aspect of Mount Saint Helens is that the succession will most likely never be complete.
The most intriguing aspect of Mount St. Helens is its never-ending cycle of succession. Since different areas received different impacts from the 1980 eruption, they represent a mosaic of recovery statuses — some of which have fully recovered, whereas others are still years away from looking remotely like the original ecosystem. Yet at the same time, the active volcano looms large over the area with predictions for another eruption well within the lifetime of the developing trees. In the meantime, smaller disturbances like avalanches and erosion have reset the ecological clocks of patches. Overall, the succession following the eruption of Mount St. Helens has presented a unique opportunity to study a variety of disturbances as a result of one massive event.
