Ngaoundere Plateau
Encyclopedia
The Ngaoundéré Plateau is a highland area in the Adamawa Region of Cameroon
. It contains Tchabal Nganha, a large volcano, and many other recent volcanic structures.
north of Cameroon.
Ngaoundéré
, the capital of the Adamawa region is located on the plateau.
It lies over the Ngaoundere fault zone, which was reactivated in the Cretaceous
.
The Ngaoundere fault belongs the Central African Fault Zone. In this region the asthenosphere
upwells from a depth of about 190 km to about 120 km in a relatively narrow belt.
basement, followed by further flows that built up the plateau.
There are many trachyte
and phonolite
plugs across the plateau, and lines of cinder cones from the most recent eruptions.
The plateau contains Tchabal Nganha, a large stratovolcano
of basanitic to trachytic composition.
Nghanha is about 1,000 m high. It developed in four main events: eruption of numerous basaltic flows which form the bulk of the mountain; deposit of voluminous breccias, most of which were deeply eroded; eruption of trachytes and phonolites as thick flows; and finally basalitic activity in the summit area. Rocks date from 9.8 to 7 million years ago.
volcanism of the Ngaoundere plateau is younger (11-9 million years old) than silicic volcanism in the Western Highlands, with much more alkaline basalt
s than in the western part of the line. This has been cited as evidence that the line is not caused by movement of the plate over a hotspot
.
To the east of Ngaoundere
and Wakwa there is quaternary volcanic activity consisting of scoria cones and lava flows, maars, and tuff cones. One lava flow in this area has been dated to 0.9 million years ago.
Some of the volcanoes may be from the Holocene
period.
Cameroon
Cameroon, officially the Republic of Cameroon , is a country in west Central Africa. It is bordered by Nigeria to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Cameroon's coastline lies on the...
. It contains Tchabal Nganha, a large volcano, and many other recent volcanic structures.
Location
The plateau is between the forested south and SavannahSavannah
Savannah or savanna is a type of grassland.It can also mean:-People:* Savannah King, a Canadian freestyle swimmer* Savannah Outen, a singer who gained popularity on You Tube...
north of Cameroon.
Ngaoundéré
Ngaoundéré
Ngaoundéré or N'Gaoundéré is the capital of the Adamawa Region of Cameroon. It had a population of 152,698 . It lies at the northern end of the railway to Yaoundé and is also home to an airport. The current city was founded in approximately 1835 by the Fulani leader Ardo Njobdi, although the...
, the capital of the Adamawa region is located on the plateau.
It lies over the Ngaoundere fault zone, which was reactivated in the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
.
The Ngaoundere fault belongs the Central African Fault Zone. In this region the asthenosphere
Asthenosphere
The asthenosphere is the highly viscous, mechanically weak and ductilely-deforming region of the upper mantle of the Earth...
upwells from a depth of about 190 km to about 120 km in a relatively narrow belt.
Formation
The plateau was formed by flows of basaltic lavas that filled two broad valleys eroded into the PrecambrianPrecambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
basement, followed by further flows that built up the plateau.
There are many trachyte
Trachyte
Trachyte is an igneous volcanic rock with an aphanitic to porphyritic texture. The mineral assemblage consists of essential alkali feldspar; relatively minor plagioclase and quartz or a feldspathoid such as nepheline may also be present....
and phonolite
Phonolite
Phonolite is a rare igneous, volcanic rock of intermediate composition, with aphanitic to porphyritic texture....
plugs across the plateau, and lines of cinder cones from the most recent eruptions.
The plateau contains Tchabal Nganha, a large stratovolcano
Stratovolcano
A stratovolcano, also known as a composite volcano, is a tall, conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions...
of basanitic to trachytic composition.
Nghanha is about 1,000 m high. It developed in four main events: eruption of numerous basaltic flows which form the bulk of the mountain; deposit of voluminous breccias, most of which were deeply eroded; eruption of trachytes and phonolites as thick flows; and finally basalitic activity in the summit area. Rocks date from 9.8 to 7 million years ago.
Related volcanic zones
Although considered by many geologists to be part of the Cameroon Volcanic Line, the silicicSilicic
Silicic is a term used to describe magma or igneous rock rich in silica. The amount of silica that constitutes a silicic rock is usually put at at least 65 percent. Granite and rhyolite are typical silicic rocks....
volcanism of the Ngaoundere plateau is younger (11-9 million years old) than silicic volcanism in the Western Highlands, with much more alkaline basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
s than in the western part of the line. This has been cited as evidence that the line is not caused by movement of the plate over a hotspot
Hotspot (geology)
The places known as hotspots or hot spots in geology are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the mantle elsewhere. They may be on, near to, or far from tectonic plate boundaries. There are two hypotheses to explain them...
.
To the east of Ngaoundere
Ngaoundéré
Ngaoundéré or N'Gaoundéré is the capital of the Adamawa Region of Cameroon. It had a population of 152,698 . It lies at the northern end of the railway to Yaoundé and is also home to an airport. The current city was founded in approximately 1835 by the Fulani leader Ardo Njobdi, although the...
and Wakwa there is quaternary volcanic activity consisting of scoria cones and lava flows, maars, and tuff cones. One lava flow in this area has been dated to 0.9 million years ago.
Some of the volcanoes may be from the Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
period.