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Journal Articles Geophysical Research Letters Year : 2006

The 1998 debris avalanche at Casita volcano, Nicaragua: Investigation of the role of hydrothermal smectite in promoting slope instability

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Sophie Opfergelt
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  • PersonId : 860494
Pierre Delmelle
Bruno Delvaux
  • Function : Author

Abstract

Buildup of excess pore water pressure within highly fractured rocks is held responsible for the initiation of the disastrous 1998 debris avalanche at Casita volcano, Nicaragua. Here, we postulate that the presence of smectite clay (up to 50 wt.%) in the hydrothermally-altered bedrock contributed to slope instability. Over decades or more, the clayey material probably (i) acted as an efficient barrier to water infiltration, (ii) progressively decreased shear-strength, and (iii) gradually destabilized the overlying rock mass. These effects are explained by the shrink-swell behavior of the clay-rich bedrock. During intense rainfall, formation of incipient weak failure surfaces in the superficial rock mass could have been favoured due to rapid alteration in the mechanical properties of smectite-containing clays deposited in fracture, joint and gouge interfaces.
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Dates and versions

insu-00385857 , version 1 (04-05-2021)

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Sophie Opfergelt, Pierre Delmelle, Pascal Boivin, Bruno Delvaux. The 1998 debris avalanche at Casita volcano, Nicaragua: Investigation of the role of hydrothermal smectite in promoting slope instability. Geophysical Research Letters, 2006, 33, pp.L15305. ⟨10.1029/2006GL026661⟩. ⟨insu-00385857⟩
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