Geology Of New York Essay Research Paper

Geology Of New York Essay, Research Paper

New York s Geology The bedrock of the earth is made up of rock bodies that vary in size, shape , orientation , composition, color, and texture. These rocks makeup the bedrock, which is present everywhere. If one were to study a map of the bedrock from a verticle point of view, they would find that patterns are made by eroded edges and surfaces of rock bodies that crop out of the state. Most rock bodies are originally tubular and horizontal . Deformations of these rock bodies occur over many years due to tilting, folding, crumpling, and breaking. An example of this can be found in the rock bodies of western New York. It is composed of layers of sedementary rocks, all diffrent in thickness, that are tilted down south less then 1 degree resulting in widths of out cropped bands. The Adarondac Mountains were once tubular rock bodies, but now sweep into broad folds. This deformed-rock pattern is typical of highly metamorphosed basment rock. One can easily see this rock pattern continue in the basment as it passes beneath the b;anket of sedimentary strata that surrounds the mountains. The pattern of small blocks along the eastern border of the adirondacs resultes from faulting that dropped crustal blocks down into a gaint staircase. The Taconic Mountains east of the Hudson River Valley are huge slices of crust that were thrust into that area from the east. The heavy toothed lines show the edges of these thrust sheets. The earth’s crust in this region was “telescoped” when a volcanicisland arc collided with the edge of the continent, causing what is known as Taconian orogeny . This collision compressed the layered rock and sediment of the intervening sea, thrusting them westward onto the continent as huge, stacked -slices. The slices, which generally dipped east in a shingled arrangement, were contorted considerably in the process. When completed, the stack extended from New England past the western edge of the Hudson Valley. In the Catskill Mountains, the western edge of this transported rockremains buried beneath Devonian rock. Erosion has reduced the original thrust sheets to patches, creating windows to the rock beneath. For the most part New York s bedrock is covered by soil and other loose material, this is especailly true in area s with hunid climates. This soil and other material is a result of the weathering of surfical rocks. This regolith can remain in place, but is usually eroded, transported, and deposited by water, wind, or glacial ice. 90% of New York state bedrock is covered by surfical deposites that one more then 1 meter thick. Most of these deposits were left by a continental glacier – an ice sheet. The most abundant glacial deposit is Till . Till is compossed mostly of mud, sand, gravel, cobbles and boulders that the glacier spread over the countryside. Till can be up to 50 meters thick. Morains are elogate ridgesor strings of hills that formed at the edge of the glacier and are compossed of Till. An example of this can be found in the Ronkonkoma and Harbor Hill Moraines in Long Island. *To better understand this section refer to the physographicand tectonic maps attached to this paper* This physiographic map illustrates the rich variety of landforms in the northeastern United States and adjacent Canada. The various landforms are mainly the result of weathering and erosion, which attack different types of rock at different rates. Lowlands form on easily erodible rocks, highlands on resistant ones, with all gradations between. The distribution of rock types in a region strongly influences its physiography. The matching tectonic map shows the diverse structure of the region’s bedrock. A comparison of the physiographic and tectonic maps clearly shows how much the physiography depends on bedrock geology. Continental glaciation played a big role in the development of New York’s landscape in the recent geological past. On its far south, the glacier removed and transported soils and eroded the surface of the bedrock. As the ice melted, thisdebris (mud, sand, gravel, and boulders) was left at new sites in a great variety of depositional landforms. Melting caused the glacier to retreat across the State from south to north between 20,000 and 10,000 years ago. The hilly area in the north-central part of the map is the Grenville Province of the Canadian Shield, an area of basement rocks, which extends across the narrow Frontenac Arch into the Adirondack Mountains. The harder rocks in the arch eroded more slowly than those around them and formed the Thousand Islands in the St. Lawrence River. Present-day drainage features in the Adirondacks illustrate well glacial erosion, transportation, and deposition. The continental ice sheet converted many pre-glacial river and stream valleys into chains of lakes by carving rock basins during ice advance and by

depositing earth dams during ice retreat. The prominent northeast-trending rivers, streams, and lakes occur where faults and fracture zones greatly weakened the bedrock to make it easily eroded. In the low plains south and west of the Canadian Shield, bedrock is covered by glacial till and by layers of sand and mud deposited in meltwater lakes. This area is underlain by flat layers of sedimentary rock and is part of the Interior Lowlands,which extend westward to the Great Plains. Immediately south of Lake Ontario is a remarkable field of streamlined hills of glacial till called drumlins, s