BEYOND WALDEN

Geological and social history of America since the ice age, centered around the many glacial kettle lakes scattered across the northeastern and north-central United States.

Hartford Courant environmental columnist Thorson (Geology/Univ. of Connecticut; Exploring Stone Walls: A Field Guide to New England’s Stone Walls, 2005, etc.) explains that rivers feed and drain traditional lakes. Kettle lakes are natural wells refreshed from deep groundwater filtered through grit-free sand, all formed more than 10,000 years ago when glaciers retreated and isolated slabs of ice melted. Since glaciers never reached most of the United States, much of the country does not have them. The quintessential kettle lake is Walden Pond, but thousands of these natural treasures represent a resource that deserves to be preserved. Lacking river connections, their waters remain tranquil, deep and pure, but such isolation makes it difficult to flush away pollutants. This was not a problem in early America because cities tended to grow near more active waters, but developers and vacationers have begun to arrive in force. Thorson casts his net widely, and readers with some knowledge of geology and botany will have an easier time understanding his meticulous explanations of the science involved. Following an overview of the last ice age that emphasizes massive water flow and lake evolution, he describes the transformation of the region’s humans, plants and animals to the present day. The author’s enthusiasm shines through as he uses personal experience, literary references and the history of American popular culture—“going up to the lake” for the summer generally meant a kettle lake—to illustrate this lively chronicle of a hitherto obscure environmental feature.

A rich, exhaustive account of one of America’s threatened ecological jewels.