VANCOUVER, Wash. — On March 20, 1980, a series of small earthquakes signaled the reawakening of the Pacific Northwest’s youngest and most active volcano. Less than two months later the resulting catastrophic eruption flattened more than 150 square miles of surrounding forest. Over the last 25 years Mount St. Helens has proven a remarkable laboratory for the study of earth processes and their influence on ecosystems surrounding the volcano.

Scientists will describe some of the lessons learned from the eruption on April 18 during the second in a series of three Monday evening seminars to be held at Washington State University Vancouver. The seminar will start at 7 p.m. in Student Services Building, Room 110. The event is free and open to the public.

The seminar will feature two scientists with the United States Forest Service. Peter Frenzen, a scientist and public affairs officer, will give a presentation entitledOut of the Ash: Survival and Recolonization in a Volcanic Landscape.” Charlie Crisafulli, a research ecologist, will speak on the topic “Mount St. Helens: A Story of Survival and Revival of Life.

Frenzen, who earned a master’s degree in forest ecology from Oregon State University and a bachelor’s degree in forest biology from the University of Washington, has been conducting research on plant succession in the volcanic blast zone since the fall of 1980.

He will discuss the profound and sometimes subtle landscape changes revealed through repeat photographs taken before, just following and during the years following the 1980 eruption and how the volcano offers an opportunity to experience nature’s unbridled power and the wonder of its continuing cycle of cataclysm and renewal.

Crisafulli, who earned an associate’s degree from the State University of New York and holds a bachelor’s degree from Utah State University, where he has also been involved in graduate coursework, has been studying the ecology of plants, animals and fungi in the Mount St. Helens volcanic landscape and in adjacent old-growth forests for nearly 25 years.

He will discuss how the 1980 eruption killed or dramatically altered the types and numbers of animals that had been present before the eruption. Over the following quarter century, aquatic and terrestrial animals have undergone a remarkable recovery as individuals of hundreds of species expanded from surviving populations or invaded the new landscape from distant source populations. By 2005, most vertebrates and thousands of invertebrates had successfully colonized the disturbed area.

WSU Vancouver is located at 14204 N.E. Salmon Creek Ave., east of the 134th Street exit from either I-5 or I-205. Parking rules are enforced Monday through Friday, 7 a.m. to 7 p.m. Parking is available in the blue lot for $1.75 or at parking meters.

For the latest information about upcoming events related to the anniversary of the eruption of Mount St. Helens, visit the 25th anniversary Web page at www.fs.fed.us/gpnf/mshnvm/25th-anniversary/index.shtml.