The World's Weirdest Volcano; Ol Doinyo Lengai
Short Summary:
Ol Doinyo Lengai, a volcano in Tanzania, is unique for its low-temperature, low-viscosity natrocarbonatite lava. Unlike most volcanoes whose lava is primarily silica-based, Ol Doinyo Lengai's lava is rich in carbonate minerals, sodium, and potassium, resulting in a black lava that rapidly (within 100 hours) turns white due to atmospheric reactions. This transformation involves several unstable minerals (gregoryite and nyerereite) changing into other minerals (pirssonite, gaylussite, shortite, thermonatrite, nahcolite, trona, calcite) through hydration and other chemical processes. The video details the chemical composition and transformations of these minerals, explaining the unusual properties of Ol Doinyo Lengai's lava. The implications are primarily geological, highlighting the unusual chemical processes occurring in this unique volcanic system.
Detailed Summary:
The video begins by introducing Ol Doinyo Lengai as the world's strangest volcano due to its unique lava. This lava is low-temperature, low-viscosity, and black, but rapidly turns white within 100 hours. The reason for this unusual behavior is explained through its chemical composition.
The next section contrasts Ol Doinyo Lengai's lava with that of other volcanoes. Most volcanoes erupt lava dominated by silica (SiO2), which determines the lava's viscosity. Examples like Kilauea (50% SiO2) and Mount St. Helens (64% SiO2) are given. Ol Doinyo Lengai's lava, however, contains only 3% SiO2.
The video then explains the unique composition of Ol Doinyo Lengai's lava: it is natrocarbonatite, containing at least 50% carbonate minerals, along with high concentrations of sodium and potassium. This composition results from a rare process where phonolite magma becomes enriched in alkali elements and CO2, causing a separation of liquids similar to oil and water. This process also concentrates rare earth elements.
The rapid color change from black to white is then explained. The initial black color is due to the minerals gregoryite and nyerereite. These are unstable in the atmosphere and rapidly hydrate, transforming into other minerals like pirssonite, gaylussite, shortite, thermonatrite, nahcolite, and trona, all of which are white. The chemical formulas of these minerals are shown, and the specific transformations are detailed, including the role of water vapor in the atmosphere. The varying densities of the resulting minerals cause the lava to decompose into a fine powder.
Finally, the video concludes by summarizing the geochemistry of Ol Doinyo Lengai's lava flows, highlighting the unusual and fascinating chemical processes involved in its unique behavior. No specific quotes are highlighted, but the overall explanation focuses on the detailed chemical transformations and their impact on the lava's appearance and properties.