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The trachytic Longonot stratovolcano SE of Lake Naivasha in the Gregory Rift valley contains a 8 x 12 km caldera. Formation of the caldera accompanied large explosive eruptions about 21,000 years ago. A large central cone that was constructed within the caldera forms the 2776-m-high summit of the volcano. The younger cone is truncated by a circular, 1.8-km-wide crater. Post-caldera lavas are found on the caldera floor and the volcano's flanks, marking a late stage of effusive eruptions. A well-preserved satellitic cone is located on the NE flank. Masai tradition records a lava flow on the northern flank during the 19th century. Similarly youthful-looking lava flows occur on the SW flank.
Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).
|Start Date||Stop Date||Eruption Certainty||VEI||Evidence||Activity Area or Unit|
|1863 ± 5 years||Unknown||Confirmed||0||Anthropology||Northern flank|
|1330 BCE ± 100 years||Unknown||Confirmed||Radiocarbon (uncorrected)|
|7200 BCE ± 100 years||Unknown||Confirmed||Radiocarbon (uncorrected)|
This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.
|Ol Olongot | Olonongot|
|The broad trachytic Longonot stratovolcano SE of Lake Naivasha is seen from the flanks of Suswa volcano (SSW of Longonot) rising above the floor of the Eastern Rift Valley of Kenya. The modern cone was constructed within a broad 8 x 12 km caldera and itself contains a smaller 1.8-km-wide summit crater that gives the summit a flat profile. Post-caldera lavas are found on the caldera floor and the volcano's flanks. Masai tradition records a lava flow on the northern flank during the 19th century.
Photo by Tom Jorstad, 1990 (Smithsonian Institution).
The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.
Richard J J, Neumann van Padang M, 1957. Africa and the Red Sea. Catalog of Active Volcanoes of the World and Solfatara Fields, Rome: IAVCEI 4: 1-118.
Rogers N W, Evans P J, Blake S, Scott S C, Hawkesworth C J, 2004. Rates and timescales of fractional crystallization from 238U-230Th-226Ra disequilibria in trachyte lavas from Longonot volcano, Kenya. J Petr, 45: 1747-1776.
Scott S C, 1980. The geology of Longonot volcano, Central Kenya: a question of volumes. Phil Trans Roy Soc London, Ser A, 296: 438-466.
Thompson A O, Dodson R G, 1963. Geology of the Naivasha area. Geol Surv Kenya Rpt, 55: 1-80.
Williams L A J, Macdonald R, Chapman G R, 1984. Late Quaternary caldera volcanoes of the Kenya Rift Valley. J Geophys Res, 89: 8553-8570.