Monday, February 27, 2006

this is rather cool - how the connecticut valley formed

A Rift - Not The River - Made This Valley
By HOWARD WRIGHT February 26 2006
The Connecticut Valley is far more than just a river valley, despite the fact some people refer to it only that way.To understand how the Connecticut Valley formed, look at Lake George, located in upstate New York and site of a tragic tourist boat accident in October in which 21 people were killed.One of the nicknames for Lake George is "Queen of the American Lakes," and it is a beautiful lake with crystalline waters. Many houses and cottages dot its Adirondack shoreline. The lake's serpentine shape - 32 miles in length and a few miles in width at most - belies its geologic origin.Hundreds of millions of years ago, the mountains were pulled apart, which created a rift valley. Within the last 20,000 years, water collected in this deep valley from melting glaciers and formed a pristine lake.Lake George actually formed from two rift valleys, a northern one and a southern one, which were separated by a mountain ridge. During the ice age that started about 2 million years ago, advancing continental glaciers bulldozed through the ridge and connected the north and south valleys together, creating a sinuous depression 32 miles in length. Disrupted drainage patterns and melting ice filled the valley with cold, clear waters, creating the lovely deep lake we see today. One striking feature of the lake is the way the mountainsides seem to plunge right into the water. In fact, the Mohawks called the lake Andia-to-roc-te, "The Lake Where the Mountains Close In."The Connecticut Valley also was formed by mountains that were pulled apart when the supercontinent called Pangaea broke up during the Mesozoic Era. North America and Africa had been stuck together for many millions of years, but about 200 million years ago they rifted apart, and for a while our little state was caught in the middle. As if in a taffy pull, tiny Connecticut was stretched in opposite directions until a large block of rock layers broke away from the eastern and western portions of the state, and a rift valley formed. For a period of about 15 million years, the valley floor slowly sank, only to be filled up by river and lake sediments and lava flows. Today, the lowlands of the valley are in contrast to the highlands of the eastern and western parts of the state. The Connecticut Valley is referred to by geologists as the Hartford basin, and it owes its origins to tectonic forces, not to erosion forces. The valley can be traced from New Haven all the way up to the Massachusetts/Vermont border. Actually, this valley is made of two rift valleys (like Lake George). Just north of Exit 17 on I-91 in Holyoke, Mass., is a 1,000-foot-high ridge of rock layers (principally made of erosion-resistant rocks from those long-ago lava flows), which separates the Hartford basin to the south from the smaller Deerfield basin to the north............

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