The geology of Delaware consists of two physiographic provinces located in the U.S. state of Delaware. They are the Atlantic Coastal Plain and the Piedmont.
The geology of Delaware consists of two physiographic provinces located in the U.S. state of Delaware. They are the Atlantic Coastal Plain and the Piedmont.
The coastal plain in Delaware is by far the largest province, encompassing all of the state south of the Kirkwood Highway from Newark to Wilmington. [1] The unconsolidated sediments of the coastal plain range in age from Cretaceous to recent. They consist of gravels, sands, silt, and clay, with varying mixtures of all four. The oldest layer, the Potomac Formation also contains some scattered lignite.
As recently as five million years ago, much of present-day Delaware was submerged as the floor of a shallow sea, the Salisbury Embayment; only with the retreat of global sea levels in recent geologic times did the coastal plain areas of the state emerge as dry land.
Delaware has a 25-mile (40 km) coastline that includes the communities of Rehoboth Beach, Dewey Beach, Bethany Beach, South Bethany, and Fenwick Island. Headlands are located at Rehoboth and Bethany and one inlet, Indian River Inlet serves as the only "natural" access to Rehoboth and Indian River Bays. The other areas are known as bay barriers and provide the only separation from the Atlantic Ocean from the lagoons.
Off shore there are two shoal fields; Hen and Chickens shoal and Fenwick Island shoal. These two areas pose a hazard to boaters. The longshore drift along the coast is generally north with a node just below South Bethany moving the sand south toward Ocean City, Maryland. Further offshore, the Delaware River paleovalley, which existed during the most recent ice age, is filled with recent sediments scoured and re-deposited as sea level rose. [2]
The Piedmont Physiographic Region of Delaware only includes the hills of northern New Castle County, which rise to approximately 400 feet (120 m) above sea level. The Piedmont extends into neighboring Pennsylvania and Maryland.
The rocks exposed in the Piedmont are metamorphic and igneous rocks that are approximately half a billion to 1.2 billion years old. The only Precambrian rock unit is the Baltimore Gneiss. Cambrian to Ordovician rocks include Wilmington Complex, Setters Formation, Cockeysville Marble, and Wissahickon Formation. Silurian rocks include the Iron Hill Gabbro, Bringhurst Gabbro, and Arden Plutonic Supersuite . The cities of Wilmington and Newark lie at the Fall Line, where the northern margin of the younger Cretaceous coastal plain sediments overlie the older Piedmont rocks.
The Delaware Geological Survey is the primary source of information about Delaware geology and hydrogeology, such as surface and sub-surface geologic rock formations, extent and quality of aquifers, stream and groundwater monitoring, water supply, earthquakes, floods and droughts, coastal processes (tides, beach erosion), topographic mapping, state mapping and GIS coordination. DGS research and service activities are focused on five areas: (1) geology, (2) hydrology, (3) natural hazards, (4) the state geospatial framework, and (5) information dissemination. These efforts impact a wide variety of issues ranging from water resources, agriculture, environmental protection, and energy and mineral resources to economic development, land-use planning, emergency management, public health, and recreation.
Bethany Beach is an incorporated town in Sussex County, Delaware, United States. According to the 2010 Census Bureau figures, the population of the town is 1,060; however, during the summer months some 15,000 more populate the town as vacationers. It is part of the Salisbury, MD-DE Metropolitan Statistical Area.
Fenwick Island is a coastal resort town in Sussex County, Delaware, United States. According to 2020 census figures, the population of the town is 355, a 2.6% decrease over the last decade. It is part of the Salisbury, Maryland–Delaware Metropolitan Statistical Area. The town is located on Fenwick Island, a barrier spit.
South Bethany is an incorporated town in Sussex County, Delaware, United States. According to the 2010 census, the population of the town is 449, a decrease of 8.7% over the previous decade. It is part of the Salisbury, Maryland-Delaware Metropolitan Statistical Area.
The Piedmont is a plateau region located in the Eastern United States. It is situated between the Atlantic Plain and the Blue Ridge Mountains, stretching from New York in the north to central Alabama in the south. The Piedmont Province is a physiographic province of the larger Appalachian Highlands physiographic division and consists of the Piedmont Upland, and the Piedmont Lowlands sections.
White Clay Creek is an 18.5-mile-long (29.8 km) tributary of the Christina River in southern Pennsylvania and northern Delaware in the United States. It is renowned for its scenic character and is largely federally protected.
The Ogeechee River is a 294-mile-long (473 km) blackwater river in the U.S. state of Georgia. It heads at the confluence of its North and South Forks, about 2.5 miles (4.0 km) south-southwest of Crawfordville and flowing generally southeast to Ossabaw Sound about 16 miles (26 km) south of Savannah. Its largest tributary is the Canoochee River, which drains approximately 1,400 square miles (3,600 km2) and is the only other major river in the basin. The Ogeechee has a watershed of 5,540 square miles (14,300 km2). It is one of the state's few free-flowing streams.
New Jersey is a state within the United States of America that lies on the north eastern edge of the North American continent. It shares a land border with the state of New York along the north, ratified by both states after the New York – New Jersey Line War, which is its only straight line border. New Jersey is slightly larger than the country of Kuwait.
The Atlantic Plain is one of eight distinct physiographic regions of the United States. The Atlantic Plain of the United States includes portions of the coastal states of Delaware, Florida, Georgia, Maryland, Massachusetts, New Jersey, New York, North Carolina, South Carolina, and Virginia.
The state of Georgia is commonly divided into four geologic regions that influence the location of the state's four traditional physiographic regions. The four geologic regions include the Appalachian foreland, Blue Ridge, Piedmont, and Coastal Plain. These four geologic regions commonly share names with and typically overlap the four physiographic regions of the state: the Appalachian Plateau and adjacent Valley and Ridge; the Blue Ridge; the Piedmont and the Coastal Plain. The geologic regions of the state, established by geologists based on relationships between stratigraphic units, significantly influence the physiographic regional names used by physical geographers. Geologic regions of the state, however, do not perfectly coincide with physiographic regions of the state. Most geologic regions (terranes) in the state are separated from one another by major thrust faults that formed during the growth of the Appalachian Mountains. The Appalachian foreland, for example, is separated from the geologic Blue Ridge by the Talladega-Cartersville-Great Smoky fault. The geologic Blue Ridge is separated from the geologic Piedmont by the Brevard fault zone. The Fall Line, the surface expression of the Coastal Plain unconformity, is the geologic boundary between the Piedmont and the Coastal Plain.
The Geology of Pennsylvania consists of six distinct physiographic provinces, three of which are subdivided into different sections. Each province has its own economic advantages and geologic hazards and plays an important role in shaping everyday life in the state. From the southeast corner to the northwest corner of the state, the include: the Atlantic Plain Province province, the Piedmont Province, the New England Province, the Ridge and Valley Province, the Appalachain Province, and the Central Lowlands Province.
The Wissahickon Formation is a mapped bedrock unit in Pennsylvania, New Jersey, and Delaware. It is named for the Wissahickon gorge in Fairmount Park, Philadelphia.
New Jersey is a very geologically and geographically diverse region in the United States' Middle Atlantic region, offering variety from the Appalachian Mountains and the Highlands in the state's northwest, to the Atlantic Coastal Plain region that encompasses both the Pine Barrens and the Jersey Shore. The state's geological features have impacted the course of settlement, development, commerce and industry over the past four centuries.
The Coastal Heritage Greenway is a greenway in the U.S. state of Delaware linking many sites along the Delaware Bay and the Atlantic Ocean between Fox Point State Park in Edgemoor, New Castle County and the beach town of Fenwick Island in Sussex County. The greenway follows Delaware Route 9 from the Wilmington area to just south of Dover and Delaware Route 1 from Dover to Fenwick Island.
Iron Hill is a prominent geographical feature in the vicinity of Newark, Delaware, in the United States. With a topographic prominence of 200 feet (61 m), it is the most prominent hill in Delaware. However, its peak elevation of 328 feet (100 m) means that it is not the state's highest point, which is located in the Piedmont plateau region near Centreville where a peak elevation of 448 feet (137 m) is attained at Ebright Azimuth. The hill is named for its iron deposits, which were mined over a 200-year period during the 18th and 19th centuries. It is part of a New Castle County park known as Iron Hill Park.
Suzette M. Kimball is an American geologist and environmental scientist who served as the 16th Director of the United States Geological Survey (USGS), a bureau of the United States Department of the Interior.
The Trenton Prong is a physiographic subprovince of the Piedmont Uplands section of the Piedmont province of the Appalachian Mountains. The prong consists of crystalline metamorphic rock.
The geology of Virginia began to form 1.8 billion years ago and potentially even earlier. The oldest rocks in the state were metamorphosed during the Grenville orogeny, a mountain building event beginning 1.2 billion years ago in the Proterozoic, which obscured older rocks. Throughout the Proterozoic and Paleozoic, Virginia experienced igneous intrusions, carbonate and sandstone deposition, and a series of other mountain building events which defined the terrain of the inland parts of the state. The closing of the Iapetus Ocean, to form the supercontinent Pangaea added additional small landmasses, some of which are now hidden beneath thick Atlantic Coastal Plain sediments. The region subsequently experienced the rifting open of the Atlantic Ocean in the Mesozoic, the development of the Coastal Plain, isolated volcanism and a series of marine transgressions that flooded much of the area. Virginia has extensive coal, deposits of oil and natural gas, as well as deposits of other minerals and metals, including vermiculite, kyanite and uranium.
The geology of North Carolina includes ancient Proterozoic rocks belonging to the Grenville Province in the Blue Ridge. The region experienced igneous activity and the addition of new terranes and orogeny mountain building events throughout the Paleozoic, followed by the rifting of the Atlantic Ocean and the deposition of thick sediments in the Coastal Plain and offshore waters.
39°42′N75°42′W / 39.7°N 75.7°W
