Observing a Gal�pagos Volcano from Buildup to Eruption

Insights from a 13-year monitoring program of Sierra Negra—one of the many volcanoes that dot the Gal�pagos Islands—shed light on the volcanic evolution of basaltic eruption.

The 2018-2019 Mayotte volcano-tectonic crisis: insights from electromagnetic experiments

<p>Since May 2018, the Mayotte Island (Comoros archipelago) is ongoing the largest basaltic eruption of the three last centuries, with up to several km3 deduced from modeling and direct seafloor observations. During this volcano tectonic crisis, we performed a land and shallow marine Magnetotelluric (MT) survey on the island the closest to the new volcano. Initially designed for shallow geothermal exploration (<2km depth), we extended the duration of the measurements to perform deep MT soundings (>10km depth) and get some insight into the geo-electric structure of the Mayotte island.</p><p>The analysis of the MT data shows a deep geo-electrical anisotropy in the W-NW E-SE direction that is coherent with the expected orientation of the oceanic ridge between the Somalian and the Lwandle plate. Additionally, the 3D inversion of the data shows that a massive conductive body is present at great depth (>15km), possibly related to the presence of partial melt. Interestingly, this conductor seems to become shallower in the direction of the new volcano.</p><p>After the survey, we installed two permanent MT stations in Petite Terre and Grande Terre islands to monitor possible time-lapse conductive anomaly related to fluid migration. We will show the results and discuss the Time Lapse MT strategy, challenges and observations.</p>

GROUNDWATER POTENTIAL IN LY SON ISLAND AND ORIENTATION OF EXPLOITATION AND USE

Ly Son is an island district of Quang Ngai province consisting of two islands: Big island and small island. With an area of about 8.7 km2, big island has 2 aquifers. The unconsolidated formation aquifer (qh) has a narrow distribution in the coastal strip with a small thickness, most of the area of the groundwater is saline, meaningless for water supply. The basaltic eruption formation aquifer (βq) is widely distributed, occupying 85% of the island’s area and has moderate water potential and there is capability for construction of public wellfields with small scale of water supply. Potential for groundwater reserves in the βq aquifer is quite abundant: Exploitation potential reserves is 12,638 m3/day, the exploitable reserve is 5,203 m3/day, the exploited reserve classified as class C1 is 3,531 m3/day, enough to meet the current and future water demand in the island. Groundwater exploitation in the island is mainly spontaneous, leading to the risk of salinity intrusion, contamination. It is necessary to rectify this situation with public exploitation solutions and have solutions to protect and develop water resources in a rational way to ensure sustainable development.