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Block analysis from lava dome collapse deposits

Thomas Johnston 1, Claire Harnett1, Pete Rowley2, Nick Varley3, Damiano Sarocchi4, Anibal Montenegro-Rios4

  • Affiliations: 1School of Earth Sciences, University College Dublin, Dublin, Ireland; 2School of Earth Sciences, University of Bristol, Bristol, UK; 3Facultad de Ciencias, Universidad de Colima, Colima, México; 4Instituto de Geología, Universidad Autónoma de San Luis Potosí, San Luis Potosí, México

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 180

  • Programme No: 3.5.39

  • Theme 3 > Session 5

Abstract

Lava domes are an unstable accumulation of viscous lava at an active volcanic vent. Dome collapses can generate block-and-ash flows (BAFs), which are typically small volume (<0.5 km3) and contain a proportion of dense, juvenile blocks derived from the source dome, and a fines fraction comprising ash generated by attrition and abrasion of the juvenile material. Volcán de Colima is a stratovolcano in the western portion of the trans-Mexican volcanic belt which undergoes frequent periods of dome growth and destruction. The collapse of the recent lava dome on the 10th and 11th July 2015 produced two BAFs that deposited along the Montegrande and San Antonio barrancas. With runout distances of 10.7 km along the Montegrande barranca and 6.5 km along the San Antonio barranca; and a total estimated volume of 4.5 x 106 m3. During this eruption, blocks originated from the collapse of the freshly emplaced lava dome as well as the crater rim. Grain size analysis is typically limited to particles <64 mm in diameter, even though blocks of several metres in size can be found throughout the deposits. We sampled both fine material and blocks at 1 km intervals along the Montegrande barranca. By combining characterisation of the sampled materials with drone surveys and image analysis, we present here a robust particle size distribution particularly focused on characterising blocks within the flow. We use these new data to infer conditions in the lava dome prior to collapse, current conditions, and transport capacity.