Deriba Crater
Encyclopedia
Deriba Crater is at the highest point of Jebel Marra at an elevation of 3,042 m (9,980 ft), in Darfur
in the western part of Sudan
. The caldera rim became Sudan's new highest point, after the independence of South Sudan
. It is between 5 km and 8 km in diameter across the outer crater. The inner crater is filled by a crater lake
.
The Marra Mountains are part of a large geologic feature known as the Darfur Dome
. The dome appears to be the result of a mantle plume
, which is a fixed “hotspot” in the Earth’s mantle (the layer of Earth below the crust). The mantle plume heated the crust from below, leading to uplift of the crust and providing a magma
source for the extensive volcanism observed in the region. The 5-kilometer-wide Deriba Caldera was formed by explosive eruption of the Jebel Marra Volcano approximately 3,500 years ago. The volcano is considered dormant, rather than extinct, as hot springs and fumaroles (gas and steam vents) are still present.
The caldera
has the classic circular shape: the depression formed as overlying rock and soil collapsed into the magma chamber after it was emptied by powerful eruptions. Following the formation of the main outer crater, a second inner crater (image center) formed, most likely due to later uplift and eruption of fresh magma moving towards the surface. This inner crater is filled with water.
Because the walls of the inner crater are higher than the adjacent caldera floor, precipitation flowing inwards from the outer crater walls does not enter the inner crater lake
. White stream bed sediments (image center) show the water pathway around the inner crater to a second lake located along the northeast wall of the outer crater. While Jebel Marra is high enough (3,042 meters) to have a temperate climate and high precipitation, these lakes may be fed by hot springs as well as rainwater.
Darfur
Darfur is a region in western Sudan. An independent sultanate for several hundred years, it was incorporated into Sudan by Anglo-Egyptian forces in 1916. The region is divided into three federal states: West Darfur, South Darfur, and North Darfur...
in the western part of Sudan
Sudan
Sudan , officially the Republic of the Sudan , is a country in North Africa, sometimes considered part of the Middle East politically. It is bordered by Egypt to the north, the Red Sea to the northeast, Eritrea and Ethiopia to the east, South Sudan to the south, the Central African Republic to the...
. The caldera rim became Sudan's new highest point, after the independence of South Sudan
South Sudan
South Sudan , officially the Republic of South Sudan, is a landlocked country located in the Sahel region of northeastern Africa. It is also part of the North Africa UN sub-region. Its current capital is Juba, which is also its largest city; the capital city is planned to be moved to the more...
. It is between 5 km and 8 km in diameter across the outer crater. The inner crater is filled by a crater lake
Crater lake
A crater lake is a lake that forms in a volcanic crater or caldera, such as a maar; less commonly and with lower association to the term a lake may form in an impact crater caused by a meteorite. Sometimes lakes which form inside calderas are called caldera lakes, but often this distinction is not...
.
The Marra Mountains are part of a large geologic feature known as the Darfur Dome
Darfur Dome
The Darfur Dome or Darfur Volcanic Province is an area about 100x400 km in area in Western Sudan, the result of a volcanic plume which created its best-known and central feature, Deriba Crater. It also produced the surrounding Marra Mountains and Tagabo Hills, formed around 16 and 10 Ma., and...
. The dome appears to be the result of a mantle plume
Mantle plume
A mantle plume is a hypothetical thermal diapir of abnormally hot rock that nucleates at the core-mantle boundary and rises through the Earth's mantle. Such plumes were invoked in 1971 to explain volcanic regions that were not thought to be explicable by the then-new theory of plate tectonics. Some...
, which is a fixed “hotspot” in the Earth’s mantle (the layer of Earth below the crust). The mantle plume heated the crust from below, leading to uplift of the crust and providing a magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
source for the extensive volcanism observed in the region. The 5-kilometer-wide Deriba Caldera was formed by explosive eruption of the Jebel Marra Volcano approximately 3,500 years ago. The volcano is considered dormant, rather than extinct, as hot springs and fumaroles (gas and steam vents) are still present.
The caldera
Caldera
A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...
has the classic circular shape: the depression formed as overlying rock and soil collapsed into the magma chamber after it was emptied by powerful eruptions. Following the formation of the main outer crater, a second inner crater (image center) formed, most likely due to later uplift and eruption of fresh magma moving towards the surface. This inner crater is filled with water.
Because the walls of the inner crater are higher than the adjacent caldera floor, precipitation flowing inwards from the outer crater walls does not enter the inner crater lake
Crater lake
A crater lake is a lake that forms in a volcanic crater or caldera, such as a maar; less commonly and with lower association to the term a lake may form in an impact crater caused by a meteorite. Sometimes lakes which form inside calderas are called caldera lakes, but often this distinction is not...
. White stream bed sediments (image center) show the water pathway around the inner crater to a second lake located along the northeast wall of the outer crater. While Jebel Marra is high enough (3,042 meters) to have a temperate climate and high precipitation, these lakes may be fed by hot springs as well as rainwater.
External links
- Location map (small scale) : http://www.geonomy.com/geonomy/viewHome.do?zoom=6&lat=12.95&lon=24.27&searchText=Marrah%20Mountains
- Satellite image (large scale) : http://www.satelliteviews.net/cgi-bin/w.cgi?c=su&DG=LKSC
- Oblique aerial photo on page 27 (large scale) : http://www.oup.com/uk/orc/bin/9780199254699/ch02.pdf
- Deriba Caldera at NASA Earth ObservatoryNASA Earth ObservatoryNASA Earth Observatory is an online publishing outlet for NASA which was created in 1999. It is the principal source of satellite imagery and other scientific information pertaining to the climate and the environment which are being provided by NASA for consumption by the general public...