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Catastrophic emplacement of giant landslides aided by thermal decomposition : Heart Mountain, Wyoming.

Mitchell, Thomas M. and Smith, S.A.F. and Anders, M.H. and Di Toro, G. and Nielsen, S. and Cavallo, A. and Beard, A. D. (2015) 'Catastrophic emplacement of giant landslides aided by thermal decomposition : Heart Mountain, Wyoming.', Earth and planetary science letters., 411 . pp. 199-207.

Abstract

The Heart Mountain landslide of northwest Wyoming is the largest known sub-aerial landslide on Earth. During its emplacement more than 2000 km3 of Paleozoic sedimentary and Eocene volcanic rocks slid >45 km on a basal detachment surface dipping 2°, leading to 100 yr of debate regarding the emplacement mechanisms. Recently, emplacement by catastrophic sliding has been favored, but experimental evidence in support of this is lacking. Here we show in friction experiments on carbonate rocks taken from the landslide that at slip velocities of several meters per second CO2 starts to degas due to thermal decomposition induced by flash heating after only a few hundred microns of slip. This is associated with the formation of vesicular degassing rims in dolomite clasts and a crystalline calcite cement that closely resemble microstructures in the basal slip zone of the natural landslide. Our experimental results are consistent with an emplacement mechanism whereby catastrophic slip was aided by carbonate decomposition and release of CO2, allowing the huge upper plate rock mass to slide over a ‘cushion’ of pressurized material.

Item Type:Article
Keywords:Landslide, Thermal decomposition, Heart Mountain, Thermal pressurization, High velocity friction.
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Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1016/j.epsl.2014.10.051
Publisher statement:© 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Date accepted:21 October 2014
Date deposited:28 September 2015
Date of first online publication:23 December 2014
Date first made open access:No date available

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