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Lake Ngozi

Ngozi

Caldera · Tanzania · 2614m

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. · Photo: Photo by David Williamson, CNRS, France. · Wikimedia Commons
Type
Caldera
Country
Tanzania
Region
Eastern Africa Volcanic Regions / Rukwa Rift Volcanic Province
Elevation
2614m
Coordinates
-9.004, 33.552
Last eruption
1450
Tectonic setting
Rift zone / Continental crust (> 25 km)
Landform
Caldera
Major rock type
Trachyte / Trachydacite
Geological summary

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.

From Wikipedia

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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Eruption history

Summary (VEI over time)
Click a bar to see individual eruptions
8250 BCE~7927 BCE · 1 eruptions · max VEI 51127~1450 · 1 eruptions · max VEI ?8250 BCE5987 BCE3400 BCE1137 BCE1127

Detailed timeline

  1. 1450 (±40 yrs)VEI ?Geological estimate
    1450 – Ongoing
  2. 8250 BCEVEI 5Geological estimate
    BCE 8250 – Ongoing

External links

⚠ For reference only. Not for emergency response.