August 07, 2023

No matter the passage of time, man’s imprint on the environment is difficult to erase, whether it occurred decades, centuries or millennia ago. If you were to get a bird’s eye view of the Susquehanna River, you might see something known as a fish weir. The long V-shaped walls were built of stacked rocks by Native Americans and early European settlers to trap fish.

Jennifer Elick, associate professor of earth and environmental sciences at Susquehanna University, and two of her students are studying how these weirs contributed to the formation of islands within the river.

“During the pandemic, I began mapping fish weirs using Google Earth Pro and noticed large gravel bedforms that appeared to have formed after major flood events,” Elick said. “I also noticed triangular shaped gravel bars and islands. As I looked back at historical images from 1938–39, I noticed that in some cases fish weirs were present, but they changed over time into gravel bars or vegetated islands.”

Coal waste found within foundation of islands

Elick and her students, Olivia Weaver ’25, an earth and environmental sciences major from Sunbury, Pennsylvania, and Sylvia Kniss ’26, an earth and environmental sciences major from Kempton, Pennsylvania, have focused their attention on one island in particular: an unnamed island near Beach Haven, Pennsylvania, in Luzerne County. They analyzed sediment samples and determined that a large percentage of the soil composition is anthracite coal and waste produced from coal-burning — magnetic glass, hematite, shale chips, coke and metals. They have also found evidence that suggests 1972’s Hurricane Agnes flood is responsible for a large deposition of sediment at the Beach Haven island.

“This also would apply to other islands and tells us that high-energy events like floods can be a contributor to the formation of these islands,” Kniss said.

Normally, the islands they were studying would be referred to as alluvial bar islands, having seemingly been formed by flooding. But what the researchers found suggested otherwise.

“Their formation is due to a manmade structure blocking or catching sediment in the river, and that sediment consists of a high percentage of manmade waste,” Weaver said. “This would make legacy islands unintentionally anthropogenic, which is why we are categorizing them under a new name.”

The name “legacy islands” comes from the anthropogenic, or manmade, nature of the islets and the legacy human actions have left behind.

Most trees date to 1970s

One of the final things Elick and her students did during their summer research was to core trees to establish the dendrochronology – approximate age – of the forest. All the trees sampled were less than 46 years old, Elick said.

“We interpreted this to indicate that the 1972 flood cleared the island out – removed all the sediment and left gravel. The 1975 flood may have also impacted recovery,” she explained. “The oldest tree started growing sometime in 1977, and as it and other vegetation grew, the island stabilized, and more sediment and trees could be established.”

Kniss and Weaver said their summer research experience will support them in their future career endeavors, in Kniss’ case to give her a foundation from which to determine her postgraduate journey.

“This experience has showed me what research is like and allowed me to learn new technologies and processes,” Kniss said.

Weaver hopes to work for an environmental consulting firm.

“This experience has given me a peek into what the research process is like and the kinds of questions and responsibilities that accompany taking on a new project that hasn’t been heavily studied,” Weaver said. “I am grateful to Dr. Elick for being an excellent mentor throughout this process. She has involved both Sylvia and me in every step of research.”

Learn more about Susquehanna’s Department of Earth & Environmental Sciences.