Natrocarbonatite is a rare carbonatite lava which erupts from the Ol Doinyo Lengai volcano in Tanzania within the East African Rift of eastern Africa. Natrocarbonatite lavas were first documented in 1962, by J. B. Dawson. [1] [2]
Natrocarbonatite is a rare carbonatite lava which erupts from the Ol Doinyo Lengai volcano in Tanzania within the East African Rift of eastern Africa. Natrocarbonatite lavas were first documented in 1962, by J. B. Dawson. [1] [2]
Whereas most lavas are rich in silicate minerals, the natrocarbonatite lavas of Ol Doinyo Lengai are rich in two rare sodium and potassium carbonate minerals, nyerereite and gregoryite. [3]
Due to this unusual composition, the lava is erupted at relatively low temperatures (approximately 500–600 °C). [4] This temperature is so low that the molten lava appears black in sunlight, rather than having the red glow common to most lavas. It is also much more fluid than silicate lavas.
The sodium and potassium carbonate minerals of the lavas erupted at Ol Doinyo Lengai are unstable at the Earth's surface and susceptible to rapid weathering, the minerals are anhydrous and when they come into contact with the moisture of the atmosphere, they begin to react extremely quickly.
The black or dark brown lava and ash erupted begins to turn white within a few hours. The resulting volcanic landscape is different from any other in the world.
Notable appearances
Magma is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural satellites. Besides molten rock, magma may also contain suspended crystals and gas bubbles.
Kogarkoite is a sodium sulfate fluoride mineral with formula Na3(SO4)F. It has a pale blue color, a specific gravity of about 2.67 and a hardness of 3.5. The crystal is monoclinic and is a type of naturally occurring antiperovskite. Kogarkoite is named after the Russian petrologist Lia Nikolaevna Kogarko (born 1936) who discovered the mineral.
Volcanic rocks are rocks formed from lava erupted from a volcano. Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and metamorphic rocks and constitute an important element of some sediments and sedimentary rocks. For these reasons, in geology, volcanics and shallow hypabyssal rocks are not always treated as distinct. In the context of Precambrian shield geology, the term "volcanic" is often applied to what are strictly metavolcanic rocks. Volcanic rocks and sediment that form from magma erupted into the air are called "pyroclastics," and these are also technically sedimentary rocks.
Nephelinite is a fine-grained or aphanitic igneous rock made up almost entirely of nepheline and clinopyroxene. If olivine is present, the rock may be classified as an olivine nephelinite. Nephelinite is dark in color and may resemble basalt in hand specimen. However, basalt consists mostly of clinopyroxene (augite) and calcic plagioclase.
Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size, or emplacement mechanism.
Carbonatite is a type of intrusive or extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geochemical verification.
Combeite is a rare silicate mineral with the formula Na2Ca2Si3O9. It has a trigonal crystal system.
Lava lakes are large volumes of molten lava, usually basaltic, contained in a volcanic vent, crater, or broad depression. The term is used to describe both lava lakes that are wholly or partly molten and those that are solidified.
Nyerereite is a very rare sodium calcium carbonate mineral with formula Na2Ca(CO3)2. It forms colorless, platey pseudohexagonal orthorhombic crystals that are typically twinned. It has a specific gravity of 2.54 and indices of refraction of nα=1.511, nβ=1.533 and nγ=1.535. Nyerereite is not stable in contact with the atmosphere and rapidly breaks down. Collection specimens must be kept in a sealed argon environment.
Baltis Vallis is a sinuous channel on Venus ranging from 1–3 km (0.62–1.86 mi) wide and ~6,800 km (4,200 mi) long, slightly longer than the Nile and the longest known channel of any kind in the Solar System. It is thought the channel once held a river of lava. It is a single channel over most of its length, but anastomoses in several sections, for lengths of up to 400 km (250 mi). There appear to be other, smaller channels in the same area, down to the limit of resolution, some of which seem to be tributaries of Baltis Vallis.
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or underwater, usually at temperatures from 800 to 1,200 °C. The volcanic rock resulting from subsequent cooling is also often called lava.
Igneous rock, or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava.
Gregoryite is an anhydrous carbonate mineral that is rich in potassium and sodium with the chemical formula (Na2,K2,Ca)CO3. It is one of the two main ingredients of natrocarbonatite, found naturally in the lava of Ol Doinyo Lengai volcano of Arusha Region, Tanzania, and the other being nyerereite.
The Tanzania Craton is an old and stable part of the continental lithosphere in central Tanzania. Some of the rocks are over 3 billion years old.
The Igwisi Hills are a volcanic field in Kaliua District of Tabora Region of Tanzania. Three tuff cones are found there, one of which is associated with a lava flow. They are one of the few locations of possibly kimberlitic lava flows on Earth.
The Alnö Complex or Alnö Alkaline Complex is a group of carbonatite and alkaline igneous rocks in Alnö in the eastern coast of central Sweden that intruded the basement in Late Ediacaran times. The Alnö Complex is made up by a series of concentric dykes within a radius of 25 km of a main "central complex" of intrusions. In addition the Alnö Complex proper is surrounded by a 500 to 600 m broad zone of metasomatic rock that was formed by metasomatic alteration of the existing Precambrian migmatite gneiss basement. The specific type of metasomatic rock is referred by some authors as "fenite". The dykes of the complex consist of carbonatite and alkaline rocks such melilite and sövite.
Ol Doinyo Lengai is an active volcano in northern Tanzania. It consists of a volcanic cone with two craters, the northern of which has erupted during historical time. Uniquely for volcanoes on Earth, it has erupted natrocarbonatite, an unusually low temperature and highly fluid type of magma. Eruptions in 2007–2008 affected the surrounding region.
Kerimasi Volcano, also known as Kerimasi at 2,602 metres (8,537 ft) is an extinct shield volcano located in Monduli District of Arusha Region in Tanzania. The majority of the mountain lies in Engaruka Ward, and a quarter of it is in the Ngorongoro Conservation Area. The volcano is located in the geographic area known as the Crater Highlands and is a shield volcano that last erupted in the Pleistocene.
Saidman volcano, also known as Sadiman or Satiman, is 2,879-meter-high stratovolcano located in Ngorongoro District of Arusha Region in Tanzania. The volcano is located in the geographic area known as the Crater Highlands and is a volcano that last erupted in the Pleistocene. The age of Sadiman volcano is unknown, with one source claiming a Pleistocene age and another claiming a K-Ar age of 4.5 million. Sadiman lava clasts have been discovered in layers dating back 1.7 to 2.0 million years. This volcano is part of the Serengeti-Ngorongoro UNESCO Biosphere Reserve in partnership with the Ngorongoro Conservation Area.
 | This volcanology article is a stub. You can help Wikipedia by expanding it. |