Was the lethal eruption of Lake Nyos related to a double CO2/H2O density inversion?

Jacques Touret, Michel Grégoire*, Merlin Teitchou

*Corresponding author for this work

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

The 1986 lethal eruption of Lake Nyos (Cameroon) was caused by a sudden inversion between deep, CO2-loaded bottom lake waters and denser, gas-free surface waters. A deep CO2 source has been found in fluid inclusions which occur predominantly in clinopyroxenes from lherzolitic mantle xenoliths, brought to the surface by the last erupted alkali basalts. P-T conditions of CO2 trapping correspond to a gas density equal (or higher) than that of liquid water. It is suggested that this dense CO2, found in many ultrabasic mantle xenoliths worldwide, has accumulated at km depth, below a column of descending lake water. It may remain in a stable state for a long period, as long as the temperature is above the density inversion temperature for pure H2O/CO2 systems. At an estimated depth of about 3 km, cooling by descending waters (to about 30 °C) induces a density inversion for the upper part of the CO2 reservoir. This causes a constant, regular upstream of low-density CO2 which, in its turn, feeds the shallower lake density inversion.

Original languageEnglish
Pages (from-to)19-26
Number of pages8
JournalComptes Rendus - Geoscience
Volume342
Issue number1
DOIs
Publication statusPublished - Jan 2010
Externally publishedYes

Keywords

  • Density inversion
  • Fluid inclusions
  • Gaseous eruption
  • Lake Nyos (Cameroon)
  • Mantle xenoliths

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