Changes in the thermal energy and the diffuse 3He and 4He degassing prior to the 2014-2015 eruption of Pico do Fogo volcano, Cape Verde

Abstract

<p>Cape Verde archipelago is a cluster of several volcanic islands arranged in a westward opening horseshoe shape located in the Atlantic Ocean, between 550 and 800 km-west of the coast of Senegal (Africa). Fogo Island is located in the southwest of the archipelago, and as main feature is a 9-km-north to south wide collapse caldera opened toward the east, within Pico do Fogo volcano rises 2,829 m.a.s.l. Pico do Fogo crater has an area of 0.142 km<sup>2</sup> and its characterized by a fumarolic field composed by low and moderate temperature fumaroles, with temperatures around 95ºC and reaching 400ºC respectively. The last eruption of Fogo volcanic system took place between November 2014 and February 2015, when four new eruptive vents were formed, and destroyed partially the villages of Portela and Bangaeira (Silva et. al., 2015) forcing the evacuation of 1,300 inhabitants. In this work we present the temporal evolution of <sup>3</sup>He/<sup>4</sup>He isotopic ratio, <sup>3</sup>He and <sup>4</sup>He emission and thermal energy released data measured from March 2007 to November 2018 in the crater of Pico do Fogo. In all the studied temporal evolutions, we can observe two main increases in the above parameters, the first in early 2010, suggesting a magmatic intrusion, and the second several months before the eruption onset. We have also observed that changes in the <sup>3</sup>He emission might be accompanied by a significant increase in thermal output if the system is in an eruptive cycle. Our results confirm <sup>3</sup>He emission studies are highly reliable indicator of imminent volcanic eruption and constitute a powerful tool to monitor the activity of volcanic areas around the world.</p><p>Silva et al., (2015), Geophysical Research Abstracts Vol. 17, EGU2015-13378, EGU General Assembly.</p>