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lago Ngozi

Ngozi

Caldera · Tanzania · 2614 m

Lake-filled Ngozi caldera is seen here from its southern rim. The 1.5 x 2.5 km caldera lake is bounded by steep-walled cliffs 150-300 m high. The caldera is the most prominent volcanic feature of the Poroto Ridge, a transverse structure at the northern end of the Karonga basin in SW Tanzania. Numerous cones are situated along the ridge. The youngest activity along the ridge appears to have originated from Ngozi caldera and from pyroclastic cones to the N.
Lake-filled Ngozi caldera is seen here from its southern rim. The 1.5 x 2.5 km caldera lake is bounded by steep-walled cliffs 150-300 m high. The caldera is the most prominent volcanic feature of the Poroto Ridge, a transverse structure at the northern end of the Karonga basin in SW Tanzania. Numerous cones are situated along the ridge. The youngest activity along the ridge appears to have originated from Ngozi caldera and from pyroclastic cones to the N. · Foto: Photo by David Williamson, CNRS, France. · Wikimedia Commons
Tipo
Caldera
Paese
Tanzania
Regione
Eastern Africa Volcanic Regions / Rukwa Rift Volcanic Province
Altitudine
2614 m
Coordinate
-9.004, 33.552
Ultima eruzione
1450
Contesto tettonico
Rift zone / Continental crust (> 25 km)
Forma vulcanica
Caldera
Roccia principale
Trachyte / Trachydacite
Sintesi geologica

Ngozi caldera is the most prominent volcanic feature of the Poroto Ridge, a transverse structure at the northern end of the Karonga basin. The trachytic-to-phonolitic volcano contains a 3-km-wide caldera with a 1.5 x 2.5 km lake in the southern part of the caldera that is bounded by steep-walled cliffs 150-300 m high. Numerous pyroclastic cones are situated along the ridge. Eruption of the Kitulo Pumice, radiocarbon dated at about 10,200 cal. years before present, is though to be related to formation of the caldera. The youngest activity appears to have originated from the caldera and from youthful-looking pyroclastic cones to the north; the youngest known eruption produced a pyroclastic flow that swept at least 10 km S about 500 years ago.

Sintesi da Wikipedia

Riassunto in inglese

Lake Ngozi (or Lake Ngosi) is the second largest crater lake in Africa. It can be found near Tukuyu, a small town in the highland Rungwe District, Mbeya Region, of southern Tanzania in East Africa. It is part of the Poroto Mountains and the northern rim of the caldera is the highest point in the range. The caldera mostly composed from trachytic and phonolitic lavas. Ngozi is a Holocene caldera that generated the Kitulo pumice 12,000 years ago during a Plinian eruption, most likely in the same eruption that generated the caldera. Other eruption deposits are the Ngozi Tuff (less than thousand years ago) and the Ituwa Surge base surge deposits of uncertain age, but intermediary to the Kitulo pumice and Ngozi Tuff. The youngest activity generated a pyroclastic flow that flowed southwards for 10 km around 1450 CE. Some pyroclastic cones surround the volcano. The walls of the caldera are forested, with the exception of segments scoured by landslides and high cliffs that inhibit access to the water. The inner caldera is forested with Maesa lanceolata, Albizia gummifera and Hagenia abyssinica, far fewer tree species than neighbouring mountains consistent with the recent geological origin of the volcano. The caldera itself is not subjected to hydrothermal activity, but large subaqueous CO2 emissions and local legends of the killing power of the lake indicate a danger of limnic eruptions. The lake floor according to echosounding is flat and has no terraces.

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Storia delle eruzioni

Riepilogo (VEI nel tempo)
Fai clic su una barra per vedere le singole eruzioni
8250 BCE~7927 BCE · 1 eruzioni · VEI max. 51127~1450 · 1 eruzioni · VEI max. ?8250 BCE5987 BCE3400 BCE1137 BCE1127

Cronologia dettagliata

  1. 1450 (±40 anni)VEI ?Stima geologica
    1450 – In corso
  2. 8250 a.C.VEI 5Stima geologica
    BCE 8250 – In corso

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