Boulder sampling on Squam Lake: Unveiling glacial history beneath our feet

Squam Lake’s landscapes are more than just stunning—they’re a window into the region’s past. Thanks to a research project led by Dr. Simon Pendleton, a professor in the Environmental Science and Policy Program at Plymouth State University, we’re learning more about the geologic story of the Squam Watershed. The project, which uses cosmogenic exposure dating of glacial erratic boulders delves into the history of glaciation of the Squam watershed.

What is cosmogenic exposure dating?

Glacial erratic’s are boulders that were transported by glaciers that once covered the Squam watershed thousands of years ago and left behind, scattered across the landscape when the ice melted. Once exposed on the landscape, cosmic radiation that is constantly bombarding the earth produces specific isotopes in the rock surfaces. Dr. Pendleton and a student from Plymouth State University are collecting samples of these erratic boulders to measure the cosmogenic isotopes, which will tell them how long ago the glacier deposited them on the landscape. The samples are taken using mechanical and physical tools such as drills, hammers, and chisels, carefully removing the top surface of the boulders.

Each sample holds clues to the past, revealing when and how these boulders were deposited.

Boulder sampling locations

In partnership with Dr. Pendleton, the SLA has been providing logistical support for fieldwork, including identifying boulders and facilitating access to sampling sites. With the permission of landowners, sampling has taken place in key locations:

• Crawford Ridgepole Trail: Samples collected last month are being analyzed to understand the glacial history of the higher elevations of the watershed.
• Moon Island: A second sampling site, offering insight into boulders placed by retreating glaciers within the lake’s islands.

By studying these boulders, researchers aim to uncover the timeline of glacial retreat in the Squam Watershed, which shaped the lakes and mountains we see today.

How are the findings used?

The samples are taken to the lab, where the cosmogenic isotopes are isolated and analyzed. These findings provide data to:

1. Understand Local History – The research will reveal when the Laurentide Ice Sheet receded across the Squam Watershed, leaving behind the landscape we know and love. This history helps us understand how the Squam Lakes and surrounding mountains were formed over thousands of years.
2. Inform Climate Science – The project contributes to a larger body of work of Dr Pendleton and others studying how glacial landscapes respond to changes in climate. By better understanding the patterns of past deglaciation, scientists can make more accurate predictions about the effects of modern climate change on glaciers worldwide.

Why this matters

While the research might seem focused on ancient history, it has profound implications for our future. By piecing together the story of glacial retreat, we gain a better understanding of the interconnectedness of climate systems and the potential impacts of a warming world on modern glaciers and ice sheets

This project also highlights the value of collaboration. From Dr. Pendleton’s expertise to the SLA’s local knowledge and support, it’s a great example of how science and community partnerships can uncover secrets of our natural world.