Harris A., Mannini S., Calabro L., Calvari S., Gurioli L., Chevrel Magdalena Oryaelle, Favalli M., Villeneuve N. (2022). Forest destruction by 'a'(a)over-bar lava flow during Etna's 2002-03 eruption : mechanical, thermal, and environmental interactions. Journal of Volcanology and Geothermal Research, 429, 107621 [13 p.]. ISSN 0377-0273.
Titre du document
Forest destruction by 'a'(a)over-bar lava flow during Etna's 2002-03 eruption : mechanical, thermal, and environmental interactions
Année de publication
2022
Auteurs
Harris A., Mannini S., Calabro L., Calvari S., Gurioli L., Chevrel Magdalena Oryaelle, Favalli M., Villeneuve N.
Source
Journal of Volcanology and Geothermal Research, 2022,
429, 107621 [13 p.] ISSN 0377-0273
Forest destruction by 'a'(a) over bar lava flow is common. However, mechanical and thermal interactions between the invading lava and the invaded forest are poorly constrained. We complete mapping, thermal image and sample analyses of a channel-fed 'a'(a) over bar lava flow system that invaded forest on the NE flank of Mt. Etna (Italy) in 2002. These lava flows destroyed 231,000 trees, only 2% of which are still visible as felled trunks on the levees or at the channel-levee contact. The remaining 98% were first felled by the flow front, with the trunks then buried by the flow. Rare tree molds can be found at the rubble levee base where trees were buried by avalanching hot breccia and then burnt through, with a time scale for total combustion being a few days. Protruding trunks fell away from the flow, if felled by blocks avalanching down the levee flank, or became aligned with the flow if falling onto the moving stream. Estimated cooling rates (0.1-5.5 degrees C km(-1)) are normal for well-insulated 'a'(a) over bar flow, suggesting no thermal interaction. We find the highest phenocryst concentrations (of 50-60%, above an expected value of 30-40%) in low velocity (<0.5 m s(-1)) locations. These low velocity zones are also characterized by high trunk concentrations. Thus, the common factor behind crystal and trunk deposition is velocity. That is, when the lava slows down, crystal settling occurs and trunks are preferentially deposited. Thus, although we find no thermal or textural effects due to the presence of the forest, we do find mechanical and environmental interactions where the trees are consumed to become part of the flow.
Plan de classement
Sciences fondamentales / Techniques d'analyse et de recherche [020]
;
Géologie et formations superficielles [064]
;
Géophysique interne [066]
;
Etudes, transformation, conservation du milieu naturel [082]
Description Géographique
ITALIE ;
Localisation
Fonds IRD [F B010085890]
Identifiant IRD
fdi:010085890
