What is a bay?
A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is usually called a gulf, sea, sound, or bight. A cove is a type of smaller bay with a circular inlet and narrow entrance. A fjord is a particularly steep bay shaped by glacial activity. A bay can be the estuary of a river, such as the Chesapeake Bay, an estuary of the Susquehanna River. The land surrounding a bay often reduces the strength of winds and blocks waves. Bays may have as wide a variety of shoreline characteristics as other shorelines. In some cases, bays have beaches, which "are usually characterized by a steep upper foreshore with a broad, flat fronting terrace." In this definition, foreshore refers to the part of the shore that is exposed at low tide and is covered by water at high tide. Terrace refers to the part of the beach that is completely exposed during normal tides and surf conditions.
Geology of Raritan Bay:
The Raritan River was perhaps the major drainage channel along the ice front throughout the Wisconsin glaciation (Stages 1, 2, 3 and 4). Prior to that time the region drained southward across the saddle between the Atlantic Highlands and the Newark Basin into the Delaware River Valley. This saddle area is a very broad flood plain that preserves river terrace gravels (Pensauken Formation) from the Sangemon Interglacial State (Stage 5), as well as older Pleistocene fluvial deposits (The Bridgetown Formation). During the lowstand in sea level caused by the Wisconsin glacier, the Raritan River carved back into its headlands and captured the major drainages from the Newark Basin. As the Wisconsin glaciers melted, the Flandrian Transgression eventually flooded the deeper valleys of the Hudson, Raritan, and Arthur Kill. During warming at the end of the Pleistocene and Early Holocene, the area encompassing Raritan Bay changed from tundra to a landscape dominated by spruce and pine forests. These forests gradually gave way to the modern deciduous forest in the region by mid-Holocene time. Lagoons and bays in the area around Sandy Hook hosted oysters, hard and soft shell clams, lobsters, blue crabs, and a variety of other invertebrates common in bays in the region today. South of western Long Island, tidal flats and wetlands occupied the margins of a tidal estuary (now submerged by marine waters). Inner Raritan Bay began to fill about 2,500 years ago with large oyster beds forming along the estuarine tributaries. Sea level continued to rise about one foot per century. This rise in sea level has resulted in the landward migration of the shoreline (aided by storm-induced coastal erosion) as much as two miles in some portions of the coast since colonial times.
What is longshore drift?
Sand moves to and from the beach in an onshore-offshore direction, but it also moves along the shoreline (“longshore”). This longshore sand transport is referred to as longshore drift (fig. 2), and because of it, beaches have been called “rivers of sand.” Longshore currents on the east coast typically move north to south rather than south to north like the Gulf Stream Current. There have been special instances where the longshore currents have changed direction during storms, hurricanes, or an abrupt change of wind for a brief period of time.
The longshore current, the movement of water along the shoreline, is caused by
Logging Tasks:
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Did you visit the beach during high tide or low tide? How does this affect the beach? Use the link https://tidesandcurrents.noaa.gov/noaatidepredictions.html?id=8531680 for tide predictions in the Raritan Bay area.
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The longshore current appears to be interrupted by manmade rock structures on the beach. Is there a large build-up of sand on the structures? If so, on what side of the structures is the biggest amount of build-up?
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Most beaches in/near bays “are usually characterized by a steep upper foreshore with a broad, flat fronting terrace" according to some sources. Do Perth Amboy’s beaches support or contradict this definition based on what you see at the GZ?
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As of June 2019, earthcaches are now allowed to have a required photo logging task. Please provide a photo of yourself, your GPSr, or a personal item that proves that you have visited this site. Please post this in your log.
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Sources:
https://tidesandcurrents.noaa.gov/noaatidepredictions.html?id=8531680
https://en.wikipedia.org/wiki/Raritan_Bay
http://www.onegeology.org/extra/kids/earthprocesses/longshoreDrift.html
https://en.wikipedia.org/wiki/Bay
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