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Volcanic field elongation, vent distribution, and tectonic evolution of a continental rift: The Main Ethiopian Rift example (2016)

Mazzarini, F., Le Corvec, N., Isola, I., Favalli, M.

Geological Society of America (GSA)

In: Geosphere

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Publication Date: 2016-05-29

Description: Magmatism and faulting operate and interact in continental rifts at a variety of scales. The East African Rift, an example of an active magmatic continental rift, provides the ideal location to study the interplay between these two mechanisms. Previous work has shown that the distribution of volcanic vents and the shape of volcanic fields are linked to their tectonic environment and their magmatic system. In order to distinguish the impact of each mechanism, we analyzed four distinct volcanic fields located in the Main Ethiopian Rift; three of them (Debre Zeyit, Wonji, and Kone) are located within the rift valley, and one (Akaki) lies on the western rift shoulder. The elongation and shape of each field were analyzed based on their vent distribution using three statistical methods: the principal component analysis, the vent-to-vent distance, and the two-dimensional, symmetric Gaussian kernel density estimation method. The results of these analyses show that the elongations of the fields increase from the western shoulder toward the rift axis and are inversely proportional to their angular dispersion. In addition, we observed that none of the analyzed fields have elongation that parallels either the trends of the youngest faults or the volcano alignments. Dike intrusions inferred from the alignment analysis of volcanic centers that are located within the rift axis tend to parallel the orientation of the recent active faults. This parallelism, however, decreases from the rift axis toward the rift shoulder, which has a lower strain rate and shows a larger number of preexisting fault orientations. Our results suggest that the shape of volcanic fields in the Main Ethiopian Rift is controlled mainly by large crustal structures and/or by the lithosphere-asthenosphere–boundary geometry. Diking is principally controlled by the location of the field within the rift zone; intrusions within the rift zone are controlled mostly by the state of stress and strain rate; while intrusions on the rift shoulder are controlled mostly by the presence of preexisting fractures. This study provides a combination of statistical analyses and geological observations to study and differentiate the mechanisms involved in the formation of volcanic fields on Earth and, potentially, other planets.

Electronic ISSN: 1553-040X

Topics: Geosciences

Published by Geological Society of America (GSA)

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Experimental study of the interplay between magmatic rift intrusion and flank instability with application to the 2001 Mount Etna eruption (2015)

Le Corvec, N. ; Walter, T. ; Ruch, J. ; [et al.]

American Geophysical Union

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Publication Date: 2021-07-13

Description: Mount Etna volcano is subject to transient magmatic intrusions and flank movement. The east flank of the edifice, in particular, is moving eastward and is dissected by the Timpe Fault System. The relationship of this eastward motion with intrusions and tectonic fault motion, however, remains poorly constrained. Here we explore this relationship by using analogue experiments that are designed to simulate magmatic rift intrusion, flank movement, and fault activity before, during, and after a magmatic intrusion episode. Using particle image velocimetry allows for a precise temporal and spatial analysis of the development and activity of fault systems. The results show that the occurrence of rift intrusion episodes has a direct effect on fault activity. In such a situation, fault activitymay occur or may be hindered, depending on the interplay of fault displacement and flank acceleration in response to dike intrusion. Our results demonstrate that a complex interplaymay exist between an active tectonic fault system and magmatically induced flank instability. Episodes of magmatic intrusion change the intensity pattern of horizontal flank displacements andmay hinder or activate associated faults. We further compare our results with the GPS data of the Mount Etna 2001 eruption and intrusion. We find that syneruptive displacement rates at the Timpe Fault System have differed from the preeruptive or posteruptive periods, which shows a good agreement of both the experimental and the GPS data. Therefore, understanding the flank instability and flank stability at Mount Etna requires consideration of both tectonic and magmatic forcing.

Description: Published

Description: 5356-5368

Description: 1V. Storia e struttura dei sistemi vulcanici

Description: JCR Journal

Description: restricted

Keywords: analogue models ; strain ; stress ; eruption ; flank dynamics ; GPS ; faults ; Etna ; 04. Solid Earth::04.03. Geodesy::04.03.08. Theory and Models

Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

Type: article

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