Sierra Leone hotspot is a proposed
hotspot
Hotspot, Hot Spot or Hot spot may refer to:
Places
* Hot Spot, Kentucky, a community in the United States
Arts, entertainment, and media Fictional entities
* Hot Spot (comics), a name for the DC Comics character Isaiah Crockett
* Hot Spot (Tra ...
in the
Atlantic Ocean.
The existence of this hotspot has been inferred from the
Sierra Leone Rise and the
Ceara Rise in the
Atlantic Ocean, two submarine topographic features around the
5th parallel north
The 5th parallel north is a circle of latitude that is 5 degrees north of the Earth's equatorial plane. It crosses the Atlantic Ocean, Africa, the Indian Ocean, Southeast Asia, the Pacific Ocean, and South America.
The Pacific Ocean is at its ...
. They formed as a single
oceanic plateau
An oceanic or submarine plateau is a large, relatively flat elevation that is higher than the surrounding relief with one or more relatively steep sides.
There are 184 oceanic plateaus in the world, covering an area of or about 5.11% of the ...
that was subsequently split by the
Mid-Atlantic Ridge during the
Jurassic and
Cretaceous (
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...
).
According to the proposal by Basile ''et al.'' 2020, the Sierra Leone hotspot 201 million years ago was at the centre of the
Central Atlantic Magmatic Province, north of the
Blake Plateau off
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
. The hotspot 180-170 million years ago formed a first oceanic plateau that was subsequently split by the
Mid-Atlantic Ridge around 100 million years ago, forming the
Demerara Plateau
Demerara ( nl, Demerary, ) is a historical region in the Guianas, on the north coast of South America, now part of the country of Guyana. It was a colony of the Dutch West India Company between 1745 and 1792 and a colony of the Dutch state fro ...
and
Guinea Rise
Guinea ( ),, fuf, 𞤘𞤭𞤲𞤫, italic=no, Gine, wo, Gine, nqo, ߖߌ߬ߣߍ߫, bm, Gine officially the Republic of Guinea (french: République de Guinée), is a coastal country in West Africa. It borders the Atlantic Ocean to the we ...
. Between 90-70 million years ago the hotspot was under the
African Plate, forming the northern Bathymetrists Seamounts. The Mid-Atlantic Ridge eventually reached the hotspot, resulting 82-55 million years ago in the formation of a second oceanic plateau which was again split by the Mid-Atlantic Ridge to form the
Ceara Rise and
Sierra Leone Rise. Since then, the Sierra Leone hotspot would have been again located on the
African Plate, now generating the southern group of the Bathymetrists Seamounts. 10 million years ago it generated the Knipovich seamount.
The hotspot is currently located about west of Knipovich seamount; it is presently inactive. According to an alternative proposal by Long ''et al.'' 2020, the hotspot would now be centered on above a
seismic velocity anomaly in the mantle and in a cluster of seamounts.
Other structures influenced by the hotspot:
*
Bahamas may be a hotspot track of the Sierra Leone hotspot, which between 170-155 million years ago may have been active on the
North American Plate.
* The east-west trending
Bathymetrists Seamounts north of the Sierra Leone Rise. They were capped by
carbonates during the mid-
Eocene. Some of the northern seamounts however produce problems in plate tectonic reconstructions if they are correlated to the Sierra Leone hotspot.
*
Syenite
Syenite is a coarse-grained intrusive igneous rock with a general composition similar to that of granite, but deficient in quartz, which, if present at all, occurs in relatively small concentrations (< 5%). Some syenites contain larger proport ...
s on the
Îles de Los may be a product of the hotspot.
* Certain segments of the
Mid-Atlantic Ridge may be influenced by the hotspot.
* Knipovich seamount rises to a depth of below sea level and has a summit.
References
Sources
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{{Hotspots
Hotspots of the Atlantic Ocean