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Edifice growth and collapse of the Pliocene Mt. Kenya: Evidence of large scale debris avalanches on a high altitude glaciated volcano

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Title Edifice growth and collapse of the Pliocene Mt. Kenya: Evidence of large scale debris avalanches on a high altitude glaciated volcano
 
Creator Schoorl, Jeroen M.
 
Contributor Veldkamp, Tom
Claessens, Lieven
Van Gorp, Wouter
Wijbrans, Jan
 
Subject 40ar/39ar geochronology
lahar
phonolite
volcanic debris avalanche
kenya rift valley
pliocene
mt. kenya
 
Description The cyclic growth and destruction of the Late Cenozoic Stratovolcano Mt. Kenya have been reconstructed for its
southeastern segment. At least three major debris avalanche deposits have been reconstructed and dated. The
oldest deposits indicate an edifice collapse around 4.9 Ma (40Ar/39Ar), followed by a larger event around
4.1 Ma (40Ar/39Ar). The last and best preserved debris avalanche deposit, with still some morphological expression
covering the whole 1214 km2 SE sector, occurred around 2.83 Ma (40Ar/39Ar). This very large debris avalanche
event must have truncated the whole top of Mt. Kenya. Of the original typical hummocky relief, only
local topographical depressions are still best visible and preserved. Using known geometric empirical parameters
of the 3 preserved debris-avalanche deposits, the height of the sector collapse is estimated to be in the range of
5100–6500mabove the current height of 1000m a.s.l. near the end lobe of the VDA deposits. This demonstrates
that Mt. Kenya attained impressive altitudes during its main activity in the Pliocene, being one of the highest
mountains in that time and was most probably covered by an ice cap. Correcting for the known net eastward
tilting post eruptive uplift of approximately 500 m of the Mt. Kenya summit, our reconstruction indicates that
an at least 5.6 to 7 km a.s.l. high active Mt. Kenya existed in the Pliocene landscape between 5.1 and 2.8 Ma.
This volcano must have significantly contributed to regional environmental change, by catching rain on its eastern
slopes and projecting a rain shadowtowards the Kenya Rift valley in thewest. The last major edifice collapse
event around 2.8 Ma coincides with a major change in regional vegetation. This suggests that the truncating of
Mt. Kenya may have caused significant changes in the local climate surrounding Mt. Kenya with possible implications
for environmental change in the central Kenya Rift valley, the cradle of hominin evolution.
 
Date 2014-10-24
2017-01-05T19:44:26Z
2017-01-05T19:44:26Z
 
Type Journal Article
 
Identifier http://oar.icrisat.org/id/eprint/9358
https://mel.cgiar.org/reporting/download/hash/vPCHOyrZ
Jeroen M. Schoorl, Tom Veldkamp, Lieven Claessens, Wouter Van Gorp, Jan Wijbrans. (24/10/2014). Edifice growth and collapse of the Pliocene Mt. Kenya: Evidence of large scale debris avalanches on a high altitude glaciated volcano. Global and Planetary Change, 123, pp. 44-54.
https://hdl.handle.net/20.500.11766/5354
Limited access
 
Language en
 
Rights CC-BY-NC-4.0
 
Format PDF
 
Publisher Elsevier
 
Source Global and Planetary Change;123,(2014) Pagination 44,54