Volcanic eruptions mark the beginnings of new landscapes. Ash and lava cover existing vegetation and map out a fresh terrain. Though researchers understand how volcanic landscapes evolve over centuries, there is little understanding of how volcanic eruptions have influenced the geomorphology, or the relationship between the Earth’s surface and geological structures, according to Christopher F. Waythomas, from the United States Geological Survey.
In a new review of historic volcanic eruptions, Waythomas laid the groundwork for interpreting the effects of volcanic eruptions on shaping the Alaskan landscape. He examined four volcanoes, Redoubt, Katmai, Pavlof and Kasatochi, and found that the volcanoes played a major – if not dominant – role in shaping the ecosystems and landscapes of southern and southwestern Alaska.
Alaska, especially the state’s Aleutian arc, experiences volcanic eruptions every one or two years. Most of the time, these eruptions affect the region’s extensive glaciers.
Following an eruption, melting glacier water can pick up debris and result in dangerous mudslides, or lahars. Lahars can be so powerful that they change the shape of the landscape they travel through, Waythomas found. They can also change sediment flux in the sea and create lahar blocked lakes.
“Given the significant magnitude of many Alaska eruptions and the high frequency of occurrence of eruptive activity, it is worthwhile to examine how eruptive activity and the products of this activity have affected the geomorphic evolution of landscapes throughout the Aleutian arc,” wrote Waythomas.”This task is practical and academic because of the obvious implications for hazards to people, infrastructure, and the environment and for understanding how volcanic systems evolve in an area that is as geologically dynamic as Alaska.”
Because Alaska’s volcanoes erupt fairly frequently, they tend to be covered by a mantle of loose debris, which is easily dislodged by water flows following an eruption.
However, the varying nature of eruptions makes understanding the consequences of eruptions and lahars difficult. The state experiences both mild eruptions that spread ash across the surrounding areas and extreme events with heavy lava flow.
“The size, characteristics, and unpredictable occurrence of such flows present significant challenges for incorporating large lahars into conventional flood-hazard analyses,” wrote Waythomas.
By further studying the secondary effects of volcanic eruptions in Alaska, researchers will have a better understanding of how the events influence the hydrology, biology and form of the landscape, Waythomas added.