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The Mast-Head: Tectonic Playthings

Wed, 09/11/2019 - 12:18

I watched Monday’s sunset from the starboard deck of the ferry from New London to Orient. The Thames River shoreline was in silhouette, the sky mostly orange to the west.

Substantial houses are built on rock along the tidal portion of the river, where it opens to the Sound. More rock juts from the water, but their locations are familiar enough to boaters so most are not marked with warning buoys.

The modest Thames was named after the River Thames by English colonists in the 17th century. It is more an estuary than its namesake, a coming together of a web of rivers and streams in a roughly 1,500-square-mile watershed that extends to Rhode Island and Massachusetts, if only by a little.

The Thames is mostly a Connecticut affair, a creation of ancient tectonic fault lines and a mile of ice that covered the area 22,000 years ago, more or less.

A little more than a dozen miles to the south, Long Island’s geology is different, the product of a slightly more recent glacial edge. Bedrock lies hundreds of feet down and visible rocks of any size are just boulders, the glacier’s playthings, picked up elsewhere and dropped, the exception rather than the rule.

Between Connecticut and Long Island, what is called the Sound today was a long, freshwater lake. For a time, well before it was filled by the sea, the Race was a cascade through which the freshwater lake drained. Today, the stretch of rough water more or less southwest of Fishers Island is a fine place for catching striped bass, as is Plum Gut, through which we passed at the end of our journey.

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