Geologic Setting of the Danakil Depression The Danakil Depression is a rift valley that parallels the Red Sea in northern Ethiopia. It is a minor structure related to the rift between Africa and the Arabian peninsula. As the rift opens, the floor of the Danakil Depression subsides. After millions of years of subsidence, the deepest part of the depression is about 125 m below sea level. It is one of the lowest points on Earth. Several times during the formation of the Danakil Depression, water has overtopped the divide between the Danakil Basin and the Red Sea, flooding the basin with seawater. Thick evaporite sequences were deposited in the basin as the seawater evaporated in the hot dry climate. Some of the evaporite deposits were formed by evaporating runoff water and evaporating hydrothermal brines. The Dallol area is one of the hottest areas on Earth. The average daily maximum temperature is about 41 degrees Celsius and the annual mean temperature is about 32.2 degrees Celsius. During the rainy season, large portions of the Danakil depression can be covered with runoff water. Volcanic Activity in the Danakil Depression Much of the floor of the Danakil Depression is covered by salt flats. Other areas are covered by basalt flows, shield volcanoes and cinder cones. Several craters up to a mile across can be seen on the salt flats. These are thought to be maars formed by phreatic eruptions. The most recent eruption occurred in 1926 when a body of magma ascended toward Earths surface in the Danakil Depression near the boundary of northern Ethiopia and Eritrea. The rising magma body penetrated the salt on its way to the surface and a phreatic explosion formed a small maar about 30 m across at the eruption site. Hot Springs and the Dallol Landscape Dallol has some of the most colorful landscapes on Earth. The hot magma below heats groundwater flowing in from the surrounding highlands. This hot water moves up toward the surface and through the evaporite deposits, dissolving salt, potash and other soluble minerals. geology/stories/13/dallol/
Posted on: Mon, 04 Aug 2014 03:32:54 +0000
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