When Penn State students and citizen scientists came together to collect water samples throughout the Shaver’s Creek watershed in September 2019, they were taking part in research that began in the 1960s at a twenty-acre outdoor laboratory called Shale Hills.
Located in Penn State’s Stone Valley Forest, Shale Hills boasts steep, forested ridges and a shallow stream that runs along the valley floor. The site sits on Rose Hill shale, a common rock formation, and
hosts a one hundred-foot flux tower, water and soil sensors, wells, and boreholes, the deepest of which extends 146 feet into soil and bedrock.
Shale Hills is one of three main research sites that comprise the Susquehanna Shale Hills Critical Zone Observatory (CZO). The CZO is part of a National Science Foundation program that supports nine observatories from California to Puerto Rico.
Scientists use the term “critical zone” to describe the porous boundary layer extending from the bedrock to the treetops where terrestrial biota live. It’s where humans grow crops, raise livestock, and find drinking water and resources like lumber, granite, and iron ore. The Susquehanna Shale Hills CZO brings together researchers from across Penn State who study how rock, water, soil, air, and living
organisms interact, and how the interactions affect humans and in turn how humans impact these interactions.
“The idea behind a critical zone observatory is that if we can go to one place and measure all the geological, chemical, and biological processes occurring in the Earth’s surface, maybe we can combine all those measurements to really understand those processes,” said Susan Brantley, distinguished professor of geosciences and lead investigator of the Susquehanna Shale Hills CZO. “It has been very successful. You can understand much more about erosion by incorporating wind and tree species into your thinking as a geologist. We even bring in human activities to our models.” The Susquehanna Shale Hills CZO began in 2007 at the Shale Hills site. The researchers’ goal then was to understand how fresh water affects surface processes. The CZO expanded in 2014 to include the entire sixty-four-square mile Shaver’s Creek watershed, including the 331-acre Garner Run site in Rothrock State Forest. Herb Cole, professor emeritus of plant pathology and environmental microbiology at Penn State, gave the researchers permission to install equipment on his 160-acre working farm, also located in the watershed, in 2017.
The expansion gave the researchers the opportunity to study the processes that occur on four geologies—Rose Hill shale, sandstone, limestone, and calcareous shale—as well as how agriculture
affects these processes.
“The biggest geomorphological impact on the planet right now is what humans are doing to the surface of the Earth,” said Brantley, who is also director of the Earth and Environmental Systems Institute (EESI). “We wanted to see if we could understand what humans are doing to the Earth, what their impact is, and how it has changed natural processes.”
The researchers have deployed several hundred sensors throughout the three main catchments and the larger Shaver’s Creek watershed, said Brandon Forsythe, watershed coordinator and EESI researcher. The sensors measure everything from water temperature and conductivity to soil gas levels to cosmic ray neutrons.
Recent work has focused on using geophysical logging tools and seismic waves to map the chemical changes underneath the Shale Hills catchment. Another study found that soil microbes switch to anaerobic respiration during rainy seasons, releasing more carbon dioxide from the soil than expected. Current research at Cole Farm includes a study looking at nitrate runoff from farm fields and the potential role of pyrite in the denitrification of this runoff before it enters Shaver’s Creek and subsequently the larger Susquehanna River watershed.
Shale Hills has provided Penn State researchers with valuable watershed data for almost six decades. NSF funding, however, ends this year. Jason Kaye, professor of soil biogeochemistry, is leading an
effort to secure University funding to continue the research team’s work at Shale Hills. The team is also in talks with the Shaver’s Creek Environmental Center to turn the CZO into an outdoor classroom.
“We reached out to Shaver’s Creek Environmental Center, and one of the ideas was for me to teach a monitoring or a watershed class,” said Forsythe. “The class would focus on the different types of
sensors that we use in the field, choosing locations for monitoring, sampling and measurement protocols, and data analysis, management, and storage. We could also host sensor building workshops. I am excited by this idea and have more ideas for getting families involved in using sensors in outdoor settings such as Shale Hills.”
The classes and workshops could be tailored to Penn State or high school students, citizen scientists, or the general public, Forsythe said. The first class could begin sometime in 2021.
“Research at Shale Hills has changed our view of how water, carbon, and nitrogen move through the environment, propelling Penn State to lead in critical zone science worldwide,” Brantley said.
“The questions that drive the research change over time, but the observatory always acts as an incubator for education and research, allowing new, exciting projects to spring to life. I am looking
forward to watching how this tiny plot of forested land changes and evolves as a hotbed of activity for Penn Staters and the community into the future.”