File:Natrocarbonatite (1963 pahoehoe lava flow, Old Doinyo Lengai Volcano, East African Rift Valley, northern Tanzania).jpg
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[edit]DescriptionNatrocarbonatite (1963 pahoehoe lava flow, Old Doinyo Lengai Volcano, East African Rift Valley, northern Tanzania).jpg |
English: Natrocarbonatite (4.1 cm across) from a freshly flowing pahoehoe lava flow at Ol Doinyo Lengai Volcano back in 1963. This is from sample CML-9 of Peterson (1990) - Contributions to Mineralogy and Petrology 105: 143-155. Published chemical analyses on this very lava indicate that it has phenocrysts of gregoryite (77% sodium carbonate, 18% calcium carbonate, 5% potassium carbonate) and nyerereite (50% Ca-carbonate, 41% Na-carbonate, 9% K-carbonate), with a groundmass of 65% Na-carbonate, 20% Ca-carbonate, and 15% K-carbonate.
Ol Doinyo Lengai in eastern Africa is only active volcano on Earth that erupts carbonatite lava. All other volcanic lavas on Earth are rich in silicate minerals. Ol Doinyo Lengai lava has essentially zero silicate content. Instead, it is dominated by sodium carbonate minerals (plus some potassium carbonate and calcium carbonate). The high sodium content makes this lava natrocarbonatite. Natrocarbonatite is the rarest lava type in the world. Shown here is a sample freshly collected from an eruption back in the 1960s. Natrocarbonatite has the unfortunate tendency to alter upon exposure to the atmosphere & water. Molten natrocarbonatite has the appearance of very dark flowing mud, but it does glow red at night. After cooling, it alters relatively quickly to a whitish, crumbly material. This sample was collected before any significant chemical or physical alteration could occur. Ol Doinyo Lengai natrocarbonatite is principally composed of the minerals gregoryite and nyerereite. Gregoryite (Na1.6K0.1Ca0.15CO3; a.k.a. (Na2K2Ca)CO3) forms dark-colored, platy-shaped, glassy-looking crystals in the lava. Nyerereite (Na0.8K0.2Ca0.5CO3; a.k.a. Na2Ca(CO3)2) forms small, grayish, rounded masses in the lava. Ol Doinyo Lengai is one of many volcanoes in the East African Rift Valley, a long continental rift complex formed as the Afar Hotspot slowly rips Africa apart. Locality: Ol Doinyo Lengai Volcano, ~9.5 miles south of Lake Natron, northern Tanzania, eastern Africa. |
Date | |
Source | https://www.flickr.com/photos/47445767@N05/14842478933/ |
Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/14842478933. It was reviewed on 11 October 2020 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
11 October 2020
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current | 17:08, 11 October 2020 | 1,146 × 837 (1.63 MB) | Ser Amantio di Nicolao (talk | contribs) | Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/14842478933/ with UploadWizard |
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Pixel composition | RGB |
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Orientation | Normal |
Horizontal resolution | 700 dpi |
Vertical resolution | 700 dpi |
Software used | Adobe Photoshop CS2 Macintosh |
File change date and time | 19:44, 3 August 2014 |
Color space | Uncalibrated |
Image width | 1,146 px |
Image height | 837 px |
Date and time of digitizing | 15:43, 3 August 2014 |
Date metadata was last modified | 15:44, 3 August 2014 |