Constraints on the age of Lake Nyos, Cameroon

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doi: 10.1016/S0377-0273(99)00172-9
Authors:Freeth, S. J.; Rex, D. C.
Author Affiliations:Primary:
University of Wales, Geological Hazards Research Unit, Swansea, United Kingdom
U. S. Geological Survey, United States
University of Leeds, United Kingdom
Volume Title:Crater lakes
Volume Authors:Varekamp, Johan C., editor; Rowe, Gary L., Jr.
Source:Journal of Volcanology and Geothermal Research, 97(1-4), p.261-269; Crater lakes, terrestrial degassing, and hyper-acid fluids in the environment, Crater Lake, OR, Sept. 4-9, 1996, edited by Johan C. Varekamp and Gary L. Rowe, Jr. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0377-0273
Publication Date:2000
Note:In English. 15 refs.; illus., incl. 1 table, sketch map
Summary:The upper 40 m of Lake Nyos are retained by a weak natural dam which, if it were to fail, would not only devastate the area hit by the 1986 gas disaster but would also cause a serious flood to surge down the Katsina Ala into Nigeria. The age of the pyroclastic cone, of which the dam is the last remnant, is therefore of great practical importance to the people of the area. If the pyroclastic cone is only a few hundred years old, as some have suggested, then it is eroding away quickly and the dam must surely fail in the very near future. If, on the other hand, it is many thousands of years old, then there is less immediate cause for concern. The age of the pyroclastic cone can be constrained in three ways: (1) Two samples of basalt, one from the dam itself and one from a lava flow which post-dates the pyroclastic cone, have both yielded K-Ar ages in excess of 100,000 years. (2) Photographic evidence indicates that there has been no detectable change (>2 m) to the width of the dam since 1958. This constrains the average erosion rate and suggests that the pyroclastic cone is at least 4000 years old. (3) Cores from sediment deposited after the level of a small lake to the northeast of Lake Nyos was raised by a debris slide from the pyroclastic cone, contain no volcanic ash. A sample from the base of this sequence has yielded a radiocarbon age of 2700 years. The Lake Nyos dam must therefore be, at the very least, a few thousand years old and although its general stability must give serious cause for concern there is no reason to suspect that the rate at which it is currently eroding away is of itself sufficient to pose an immediate threat. Abstract Copyright (2000) Elsevier, B.V.
Subjects:Absolute age; C-14; Carbon; Cenozoic; Cinder cones; Crater lakes; Dates; Erosion rates; Igneous rocks; Isotopes; K/Ar; Lacustrine features; Lakes; Pleistocene; Pyroclastics; Quaternary; Radioactive isotopes; Volcanic features; Volcanic rocks; Africa; Cameroon; Lake Nyos; West Africa
Coordinates:N020000 N130000 E0170000 E0080000
Abstract Numbers:01M/911
Record ID:2000057483
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands
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