What type of geology exists in the roanoke sound

A phenomenon that is, even now, in the process of passing forever out of existence. As most people know, the level of the ocean has changed steadily throughout geological history, as a result of water released or stored up in the great polar icecaps.

When, during the ice ages, great amounts of water are withdrawn from circulation, the consequent lowering of the sea extends coastlines far out into what is now the ocean. This is, as most authorities now agree, how the Banks were formed.

They are surprisingly recent. As the last great ice age, some 20, years ago, drew to an end, the sea was more than feet lower than it is now. The area we now call North Carolina extended some 30 miles farther out, to the edge of the North American Continental Shelf.

The polar icecaps, warmed by some still mysterious climatic change, then began to melt, and the sea rose. Rivers from inland contributed silt to build them up. But as the sea rose, the dunes were submerged, becoming sand bars. Thousands of years passed. The waves kept rolling in, and the bars grew. They also moved, pushed westward and southward by the prevailing northeast winds and seas.

The rising sea flooded the low land behind them, forming estuaries that we today call the sounds. The Banks grew and broke to the surface once again. A few thousand years later, the rise in the ocean slowed, though it continues today at an accelerating rate.

The Banks had a breathing space. Life began to take root as rain leached the salt from the sand. Beach grass and other vegetation helped to keep sand in place, further slowing the rate of migration. Today the Outer Banks seem, to our short-lived eyes, a permanent land form. We see today a string of narrow, low islands, an average of 12 feet above sea level, from a few thousand feet to 3 miles across, punctuated by narrow inlets. But they're not permanent; they are alive, and they are moving even now.

Two examples:. Oregon Inlet. Note, as you drive across the Herbert Bonner Bridge, the expanse of low, flat land under the northern piers. This land was not there when the bridge was built in It's land that has moved in since then, more than a mile of it. Bodie Island is extending itself southward. All the islands are moving south. The new bridge that will be finished in the fall of will span large sections of dry land that are often inundated by ocean overwash during big storms.

If you know anything about shells, examine closely those you find at the surf line at Nags Head or Coquina Beach or Hatteras. You will notice many old fresh and brackish water snail and oyster shells. You may also see large flat chunks of what looks like dried horse manure. This is peat, formed in freshwater bogs. How did these materials get to the sea side of the islands?

Answer: They didn't move. They stayed right where they were and the islands have migrated over them. All the islands are moving west. Of course, it's all happening very slowly. But it's fascinating to understand how dynamic, moving and living the Banks are. Within these living islands, five major natural communities have evolved in response to different conditions. The Ocean Beach habitat is between the surf line and the dune line. There is little vegetation in this area, but clams, ghost crabs and a few other small marine animals exist or venture above the surf line.

Primarily the Ocean Beach habitat belongs to the birds: willets, sanderlings, plovers, terns and gulls. The foot barrier dunes along the eastern shore were stabilized with plantings of sea oats, beach grass, cordgrass, panic grasses and such shrubs as wax myrtle, bayberry and baccharis.

Mice, rabbits and small harmless snakes live here, as do toads, racerunner lizards and, again, many birds. Behind and partially protected by the dunes is the Herb-Shrub habitat. This extends clear across most of the center of the islands, except where submerged by moving dunes. Characteristic plants are wax myrtle, bayberry, yaupon, live oak, cordgrass and blackberry.

Rabbits and mice are more common there amid the dunes, and larger animals raccoons, foxes, mink are seen along with toads, frogs and lizards and their predatory snakes. The Tidal Marsh habitat is found on the sound side of most of the islands. Its cordgrass, rushes and other salt or brackish water plants nourish a vast variety of life: waterfowl, muskrats and nutria, falcons and hawks, ducks.

Much of Pea Island, a wildlife refuge famous for its birds, is marsh. Amid the sheltering roots of the marsh plants grow many of the shrimp, crabs, mollusks and fishes that later leave the marshes and enrich the sea.

The last habitat on the Banks, the Maritime Forest, is found at its widest points, where shelter from salt-carrying wind is best. Thick forests of live oak, loblolly pine, dogwood and red bay alternate with freshwater ponds.

Gray squirrel, opossum and white-tailed deer live here. The Banks were like this — wild — when human beings arrived, and history, properly speaking, began. Apparently North Carolina was settled between and A. By the late s these had diversified into various tribes, speaking dialects of the original tongue. They ranged widely along the Banks, living on fish, shellfish, wildfowl and deer and cultivating maize, beans, cucurbits a gourd like plant and sunflowers. The modern coastal geomorphology results from interaction among the underlying geologic framework, fluctuating rates of relative sea-level change, coastal oceanographic processes, and anthropogenic modifications.

Also see the park Geologic Resources Inventory Report for details on these and other coastal features and process, as well as a discussion of management issues and mapping units in this dynamic coastal setting. Landward migration of the barrier islands exposes remnants of forests and swamps that once grew on their back sides. These remnant trees and organic peat deposits are generally hundreds to hundreds of thousands of years old Dolan and Lins ; Tweet et al.

Sediments eroded from relict inlet deposits provide another source of shell fragments and other fossils of pre-Holocene age Herbert and Heron ; Tweet et al.

The offshore continental shelf produces a variety of fossils that may wash ashore, including those of algae, foraminifera, corals, bryozoans, mollusks, ostracodes, barnacles, and echinoids, as well as polychaete worm tubes Macintyre and Milliman ; Cleary and Thayer ; Culver et al. See Maps and Reports, below. Cape Hatteras National Seashore is a part of the Coastal Plain Physiographic Province and shares its geologic history and some characteristic geologic formations with a region that extends well beyond park boundaries.

Source: Data Store Saved Search To search for additional information, visit the Data Store. Show 10 40 per page. Explore This Park. In-depth geologic information is contained in the baseline inventory products of the Geologic Resources Inventory, see table below. Coastal Features and Processes Noteworthy geologic and environmental features and processes at Cape Hatteras National Seashore include the following: Oceanographic Conditions.

The Outer Banks is a storm- and wave-dominated barrier island system with low tidal ranges. Sediment Transport Processes. Waves, wind, and storm surge move sediment through the inlets and along and across the islands.

The longshore transport rate is very high. The framework geology controls sediment availability and type. New sediment comes from the eroding shoreface, updrift beaches, capeassociated shoals, and inlet deltas.

Capes and Cape-Associated Shoals. Cape Hatteras and Diamond Shoals separate two major ocean currents and biological regimes. The cold-water Labrador Current flows southward to meet the warm-water Gulf Stream, which flows northward. Their interaction and the resulting oceanographic and atmospheric responses are controlled by the geography of the continental margin, Cape Hatteras and Diamond Shoals, and the underlying geology.

New inlets open during storms, when storm surge breaches the island from the ocean or estuarine side. Tidal currents deposit sediment, building flood and ebb tidal deltas, which are important for the island sediment budget, marsh building, and long-term island evolution.

Inlets are dynamic and essential components of barrier islands and associated riverine and estuarine systems. Only three modern inlets are currently present, but up to 30 inlets have opened and closed along the Outer Banks in the last years. Pamlico and Roanoke sounds provide fish nursery and foraging habitats, and support several seagrass species. Water quality is good in most areas, but is impacted by septic leachate and other riverine pollutant input.

Estuarine sediments are derived from shoreline erosion, continental shelf, and ongoing biogenic production. Freshwater Aquifer. The shallow groundwater is recharged through rainfall, and is depleted through anthropogenic withdrawal, evapotranspiration through surface vegetation, and surface drainage from uplands.

It can also be affected by impoundments and drought.