Evolution of the Ecuadorian arc: construction periods, magmatic productivity and erosion rates

Abstract : In the northern volcanic zone of the Andes, the Ecuadorian arc presents a large number of Quaternary volcanoes, spread over a rather restricted and populated surface area. The activity of the southern termination of the arc seems partly related to the tectonic activity, while the northern part is located above the inland prolongation of the oceanic Carnegie ridge. In this study, we focus on two E-W transects, in the northern and the southern termination of the arc. The former includes Mojanda, Imbabura and Cusín, and the later Igualata, Huisla and Tungurahua volcanoes. We performed numerical reconstructions of the volcanoes flanks morphology before their erosion by using the available DEM. These reconstructions allow us to estimate the total volume of magma emitted, and the amount of eroded material due to abundant precipitations and glacial-interglacial alternating periods. Together with new groundmass K-Ar ages, these volumes are used to quantify the rates of volcanic emission of these volcanoes, as well as their erosion rates during quiescence periods. The volcanic emission rates obtained here are rather similar for both segments, ranging between 0.1 and 5.6 km3.ka-1, while the erosion rates vary between 0.01 and 0.14 km3.ka-1. Both rates are not related to the geodynamic or tectonic settings. The highest emission rates are obtained for volcanoes constructed over less than 100 ka, and could represent sporadic eruptive pulses, whereas rates calculated over longer time periods include quiescence phases and do not exceed 1 km3.ka-1. The highest erosion rates are obtained for young volcanic edifices, whose activity ended recently. These results highlight that the volcano morphology is carved by chemical and physical erosion processes that mainly depend on the age and degree of weathering of rocks.
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https://hal.archives-ouvertes.fr/hal-02365906
Contributor : Mathilde Bablon <>
Submitted on : Friday, November 15, 2019 - 3:43:48 PM
Last modification on : Tuesday, November 19, 2019 - 2:43:52 AM

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  • HAL Id : hal-02365906, version 1

Citation

Mathilde Bablon, Xavier Quidelleur, Pablo Samaniego, Jean-Luc Le Pennec, Silvana Hidalgo. Evolution of the Ecuadorian arc: construction periods, magmatic productivity and erosion rates. Cities on Volcanoes 10, 2018, Napoli, Italy. 2018. ⟨hal-02365906⟩

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