The physical geography of a region is generally defined by the nature of its topography. It is closely related to the local geology, however a distinction needs to be recognized between a locality's physical features and its geological strata. Physical features are a result of many factors, including faults and erosional characteristics of geologic units such as rock strata and layers of sediment, as well as long and short term processes such as climate change, glaciation, storms, rise and fall of sea level, vertical and horizontal tectonic movements of land areas, floods, impacts of extraterrestrial material, and the influence of vegetation. In addition, most locations contain a combination of diverse geological materials, as do the Adirondacks, where rocks more than a billion years in age are partially covered by glacial deposits less than 20 thousand years in age. To some degree, the distinction between physiographic regions is arbitrary, since this is based on determinations regarding which physical characteristics are considered diagnostic. While classification of an area into physiographic regions can gloss over some of the details, it does help characterize the essence of the landscape of the area.
Mount Colden, with rockslides, viewed from Marcy Dam on July 10, 2004. Click photo for Flickr photo page.
The United States Geological Survey provides a map of the physiographic regions of the 48 contiguous United States at
A Tapestry of Time and Terrain: The Union of Two Maps - Geology and Topography. Quoting that page:
Geomorphic, or physiographic, regions are broad-scale subdivisions based on terrain texture, rock type, and geologic structure and history. Nevin Fenneman's (1946) three-tiered classification of the United States - by division, province, and section - has provided an enduring spatial organization for the great variety of physical features.
New York State's oldest rocks were deposited in shallow seas as sediment and chemical precipitates about 1.3 billion years ago. There was life in these seas, such as stromatolites, as evidenced by fossils at the western edge of the Adirondacks. At least four major episodes of mountain building, known as orogenies, affected the region, namely the Grenville (1.1 billion years ago), Taconian (460 million years ago), Acadian (400 million years ago), and Alleghanian (300 million years ago) Orogenies. In actuality, the duration of each of these orogenies spanned tens of millions of years. The Grenville and Alleghanian Orogenies each accomplished the completion of the assembly of a supercontinent, namely Rodinia and Pangaea, respectively. Both of these supercontinents, which included nearly all the landmasses on Earth, ultimately rifted apart, Rodinia beginning about 660 million years ago, and Pangaea starting around 200 million years ago. The Atlantic Ocean and the Newark Basin are both a result of the rifting of Pangaea. The forerunner of the Atlantic Ocean, which existed after the breakup of Rodinia and prior to the assembly of Pangaea, was the Iapetus Ocean.
Stromatolite fossil, about 1.3 billion years in age, near Balmat, New York in the western Adirondacks. Click photo for Flickr photo page.
During various periods of time in the geologic past, especially the early and Middle Paleozoic Era prior to the Acadian Orogeny, large portions of New York State were covered by shallow seas. Life in these seas is represented in sedimentary rock as fossils, including tribobites, brachiopods, corals, crinoids, mollusks, bryozoans, and New York's official state fossil, the eurypterid. The Allegheny Plateau and the Erie-Ontario Lowlands of western New York State are especially fine locations for finding Early and Middle Paleozoic fossils.
During the time of the dinosaurs, the sea continued to play a role in New York State's geologic history as it does today. In the Late Cretaceous, about 95 million years ago, which was toward the end of the time of dinosaurs, a series of river deltas occupied the coastline, and they are represented by sediments beneath the surface of Long Island. Some of this material contains fossilized plant material such as species of magnolias and willows that are indicative of a warmer and moister climate than today's on Long Island. Long Island was closer to the equator back then than it is now.
Nearly all of this Cretaceous material is now covered by thick glacial deposits, which form hilly moraines and flat outwash plains on Long Island. The glacial material, which is present in almost all parts of New York State, was deposited by a series of advances and retreats of continental ice sheets during the Pleistocene Epoch, which began about 2.6 million years ago. The continental glaciers began their last retreat in New York State about 20,750 years ago. These glaciers carved out the basins of the Finger Lakes, sculpted the shapes of some of the mountains in the Adirondacks, deposited outwash plains and moraines in many regions, and left numerous elongated hills known as drumlins on the Erie-Ontario Lowlands.
Nowadays, water is the most prominent natural geologic agent that is shaping New York State's landscape, as waves break along shorelines, and rivers move sediment from elevated regions to lowlands and the sea.
The attached KMZ file demarcates New York State's major physiographic regions. It contains network links to groups of overlays of USGS topographic maps and placemarks that can be used to explore some of the physical features in these regions. After activating one or more of the network links, you can double-click a placemark on the map or within its folder in the Places pane for a pre-defined view.
Additional InformationGeneral
A Tapestry of Time and Terrain (USGS i2720)
A Tapestry of Time and Terrain: The Union of Two Maps - Geology and Topography (USGS)
Wikipedia: Physical geographyWikipedia: United States physiographic regionWikipedia: Physiographic regions of the worldPhysiographic Regions of New York State
Wikipedia: Hudson ValleyWikipedia: Adirondack MountainsWikipedia: Tug Hill PlateauWikipedia: Atlantic coastal plainWikipedia: Catskill MountainsWikipedia: Allegheny PlateauWikipedia: Saint Lawrence LowlandsWikipedia: Taconic MountainsWikipedia: Champlain ValleyGeologic Past
Wikipedia: PleistoceneWikipedia: Grenville orogenyWikipedia: Iapetus OceanWikipedia: RodiniaWikipedia: PangaeaWikipedia: MetamorphismFossils
Wikipedia: EurypteridWikipedia: TrilobiteWikipedia: BrachiopodFeatures
Wikipedia: MoraineWikipedia: Long IslandWikipedia: DrumlinWikipedia: Mount MarcyRelated Google Earth Community Threads
Adirondack MountainsLong Island Digital Elevation ModelClassic Map of Long Island Geology as an OverlayLong Island's Coastal FeaturesNew York City Region Geologic Map OverlayChanges at Fire Island Inlet since 1941Changes at Eastern End of Fire IslandBeach Drift at RockawayConnecticut Bedrock and Long Island BouldersHeadwaters of Long Island Rivers
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