The Natural History of the Cambridge Region
October 16, 2005

An audience of about 60 people gathered for this lecture by naturalist and author, Chris Leahy. The program was sponsored by Friends of Mount Auburn in conjunction with Friends of Fresh Pond Reservation

Chris described the geologic conditions that created eastern Massachusetts. Beginning with continental drift, he told how the landmass that is now Africa collided about 300 million years ago with a land called Laurentia, which is now North America. Three volcanic islands that lay between the two larger landmasses were compressed between them, and were left behind when the future Africa drifted away to the east.

Then came the glaciers, which scoured away all living things and loose material down to bedrock. The most recent, the Wisconsin stage glacier that retreated about 13,000 years ago, left behind the kettle-hole ponds we know as Fresh Pond and Spy Pond; moraines such as Avon Hill, Huron Avenue Hillside, and Cape Cod; and the dramatic terrain of Mount Auburn Cemetery.

As the glacier retreated, plants colonized the newly exposed land, with arctic species leading the way along the still-cold front edge. Gradually plants requiring warmer conditions moved in. Today the relatively low diversity of plant life in New England (as compared to much greater biodiversity in southern Africa on the same latitude in the southern hemisphere) is a reminder of the impact of the glacier.

Elizabeth Wylde