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Maine's geologic past is unknown prior to 650 million years ago, although some geologists have suggested that rocks over a billion years old may be present in units of the Chain Lakes in northwestern Maine. The state is made up of three distinct terranes, including Laurentia, Iapetus Ocean terranes and the former microcontinent of Avalonia.
Abrasion also produces rock flour which is visible in glacial outwash plains across New England. Maine has some of the longest eskers in the world. [12] As the climate began to warm, the glaciers began to melt and drainage from meltwater under the glacier formed huge torrents of sediment that, when compacted, left a long and sinuous ridge or kame.
[3] [8] [10] The remainder of the pluton then cooled at a much faster rate for another 50 million years in another phase related to tectonic uplift. [ 8 ] [ 5 ] Although the Sebago Granite is igneous in origin, the muscovite present throughout the unit indicates some partial melting of surrounding sedimentary or metasedimentary rocks at some ...
The sculptured beauty and brilliant colors of the Colorado Plateau's sedimentary rock layers have captured the imaginations of countless geologists. This is a vast region of plateaus, mesas, and deep canyons whose walls expose rocks ranging in age from billions to just a few hundred years old. [11]
It is bounded on the east by metamorphic and sedimentary rocks of the Piedmont Province. [16] The Adirondack and New England Provinces include sedimentary, meta-sedimentary, and plutonic igneous rocks, mainly of Cambrian and Ordovician age, similar lithologically to rocks in the Blue Ridge and Piedmont Provinces to the south. The uplifted ...
On a map showing only volcanic rocks, the west coast of North America shows a striking continuous north–south structure, the American Cordillera. The North American Cordillera extends up and down the coast of North America and roughly from the Great Plains westward to the Pacific Ocean , narrowing somewhat from north to south.
The most populous counties tend to be located in the southeastern portion of the state, along the Atlantic seaboard. The largest counties in terms of land area are inland and further north. Maine's county names come from a mix of British, American, and Native American sources, reflecting Maine's pre-colonial, colonial, and national heritage.
The Salmon Falls River and the Piscataqua define the southern portion of the border with Maine. The largest of New Hampshire's lakes is Lake Winnipesaukee, which covers 71 square miles (184 km 2) in the east-central part of New Hampshire. Umbagog Lake along the Maine border, approximately 12.3 square miles (31.9 km 2), is a distant second.