Chevron (land form)
Encyclopedia
A chevron is a wedge
-shaped sediment
deposit observed on coastlines and continental interiors around the world. The term chevron was originally used independently by Maxwell and Haynes and Hearty and others for large, v-shaped, sub-linear to parabolic landforms in southwestern Egypt and on islands in the eastern, windward Bahamas. The Egyptian “chevrons” are active, wind-generated dunes, but the “chevrons” in the Bahamas are inactive and have been variously interpreted. The most common interpretation of large, chevron-shaped bed forms is that they are a form of parabolic dune, and that most examples are generated by wind action.
In an alternative view, the Holocene Impact Research Group hypothesizes that the formations could be caused by tsunami
s from meteorite
impacts or submarine slides which lift sediment up and carry it hundreds of miles until depositing it on coastlines. Part of the evidence they cite for this hypothesis is that the sediments contain tiny marine fossils; however, such fossils can be moved by the wind, just like sand. The impact idea is controversial not only because chevrons are similar to wind-blown landforms found far from the ocean, but also because it is unlikely that there have been enough large impacts and landslides to explain the observed chevrons. Moreover, some computer models and sediment-transport analysis do not support this theory. For example, the orientation of chevrons along the southern coast of Madagascar do not line up with what these models of mega-tsunamis have simulated. Additional evidence against the mega-tsunami hypothesis is that the force of the water would not produce such regular bed forms.
Many chevrons can be found in Australia
, but others are concentrated around the coastlines of the world. For instance there are chevrons in Hither Hills State Park
on Long Island
and in Madagascar
(such as the Fenambosy Chevron
), as well as in interior sites of the United States such as the Palouse region of eastern Washington State, the Great Sand Dunes National Park and Preserve
, and White Sands National Monument
.
Wedge
Wedge may refer to:Mathematics:* Triangular prism, a parallel triangle wedge* Wedge , a polyhedral solid defined by two triangles and three trapezoid faces* Wedge product, a mathematical term, named for the ∧ operator symbol used...
-shaped sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
deposit observed on coastlines and continental interiors around the world. The term chevron was originally used independently by Maxwell and Haynes and Hearty and others for large, v-shaped, sub-linear to parabolic landforms in southwestern Egypt and on islands in the eastern, windward Bahamas. The Egyptian “chevrons” are active, wind-generated dunes, but the “chevrons” in the Bahamas are inactive and have been variously interpreted. The most common interpretation of large, chevron-shaped bed forms is that they are a form of parabolic dune, and that most examples are generated by wind action.
In an alternative view, the Holocene Impact Research Group hypothesizes that the formations could be caused by tsunami
Tsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...
s from meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
impacts or submarine slides which lift sediment up and carry it hundreds of miles until depositing it on coastlines. Part of the evidence they cite for this hypothesis is that the sediments contain tiny marine fossils; however, such fossils can be moved by the wind, just like sand. The impact idea is controversial not only because chevrons are similar to wind-blown landforms found far from the ocean, but also because it is unlikely that there have been enough large impacts and landslides to explain the observed chevrons. Moreover, some computer models and sediment-transport analysis do not support this theory. For example, the orientation of chevrons along the southern coast of Madagascar do not line up with what these models of mega-tsunamis have simulated. Additional evidence against the mega-tsunami hypothesis is that the force of the water would not produce such regular bed forms.
Many chevrons can be found in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, but others are concentrated around the coastlines of the world. For instance there are chevrons in Hither Hills State Park
Hither Hills State Park
Hither Hills State Park is a state park located on the southern shore near the eastern tip of Long Island in Suffolk County, New York in the USA.The park is located on the South Fork of Long Island at Napeague, New York...
on Long Island
Long Island
Long Island is an island located in the southeast part of the U.S. state of New York, just east of Manhattan. Stretching northeast into the Atlantic Ocean, Long Island contains four counties, two of which are boroughs of New York City , and two of which are mainly suburban...
and in Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
(such as the Fenambosy Chevron
Fenambosy Chevron
The Fenambosy Chevron is one of four chevron-shaped land features on the southwest coast of Madagascar, near the tip of Madagascar, 180 metres high and 5 km inland. It is composed mainly of material found on the ocean. Chevrons such as Fenambosy have been hypothesized as providing evidence of...
), as well as in interior sites of the United States such as the Palouse region of eastern Washington State, the Great Sand Dunes National Park and Preserve
Great Sand Dunes National Park and Preserve
-Other features:The park also contains alpine lakes and tundra, six peaks over 13,000 feet in elevation, ancient spruce and pine forests, large stands of aspen and cottonwood, grasslands, and wetlands — all habitat for diverse wildlife and plant species.One of the most unusual features of...
, and White Sands National Monument
White Sands National Monument
The White Sands National Monument is a U.S. National Monument located about southwest of Alamogordo in western Otero County and northeastern Dona Ana County in the state of New Mexico, at an elevation of 4235 feet...
.