The Fenambosy Chevron is one of four
chevron-shaped land features on the southwest coast of
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
, near the tip of Madagascar, high and inland. Chevrons such as Fenambosy have been hypothesized as providing evidence of "
megatsunamis" caused by
comet
A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...
s or
asteroid
An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere.
...
s crashing into
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
.
[Scheffers, A., Kelletat, D., Scheffers, S. R., Abbott, D. H., and Bryant, E. A., 2008, Chevrons – enigmatic sedimentary coastal features, ''Zeitschrift für Geomorphologie'', v. 52, no. 3, pp. 375-402.] However, the megatsunami origin of the Fernambosy and other chevrons has been challenged by other geologists and oceanographers.
[Bourgeois, J. and Weiss, R., 2009]
"Chevrons" are not mega-tsunami deposits--A sedimentologic assessment, ''Geology''
v. 37, pp. 403–406.[Pinter, N., and Ishman, S. E., 2008]
Impacts, mega-tsunami, and other extraordinary claims, ''GSA Today.''
v. 18, no. 1, pp. 37–38.
A feature called the
Burckle crater lies about east-southeast of the Madagascar chevrons and in deep ocean. it is hypothesized to be an
impact crater by the
Holocene Impact Working Group
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene together ...
. Although its
sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...
s have not been directly sampled, cores from the area contain high levels of
nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...
and magnetic components that are argued to be associated with impact ejecta.
Geologist
A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, earth science, or geophysics, althou ...
Dallas Abbott
Dallas Abbott is a research scientist at the Lamont–Doherty Earth Observatory of Columbia University and is part of the Holocene Impact Working Group. The primary focus of her present research is on submarine impact craters and their contributio ...
estimates the age of this feature to be about 4,500 to 5,000 years old.
References
External links
*Blakeslee, S., 2006
Ancient Crash, Epic Wave ''The New York Times'', November 14, 2006, last accessed September 28, 2014.
Geography of Madagascar
Geological hazards
Tsunami
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