RESUMO
The remote North Patagonian region is a sparsely populated territory and a world famous tourist destination located on the leeward side of the Andes Mountains. Recent disasters triggered by various types of geoenvironmental hazards (including volcanic eruptions, mass-wasting processes and extreme weather events) heavily disrupted ground transport networks in a region with already limited territorial accessibilities. All these catastrophes prompted the need to evacuate or assist a number of secluded visitors, locals and livestock extemporaneously on board of coastguards and tourist passenger-ships from the shores of the many glacial lakes that make up part of the regional attraction. Despite the recurrence of these types of events, water evacuations in the region continue to be spontaneous, improvised and hazardous procedures. This contribution reconstructs and assesses a number of recent local-scale cases of lake evacuations and assistances from a number of Patagonian urban centers, rural areas and tourist sites. For each case study, we systematically elaborated on the prime components of an evacuation process, which enabled us to recognize key achievements, failures and conditioning factors for managing emergencies via water transport, most of them inherent to the studied region. Some of the complexities to emerge from case studies referred to: complex hazard-related scenarios; limited ground-based accessibilities and risk of isolation; various inter- and intra-organizational issues, incidental to natural reserves and tourist regions; a wide range of particular demographic features; and the availability and vulnerability of water transport resources. We suggested fundamental and replicable recommendations for developing water evacuation plans, also identifying forthcoming problems to solve in order to improve the management of emergencies through this alternative means of transport.
RESUMO
Very fine silicate-rich volcanic ash, generated by explosive volcanic eruptions, can efficiently be traced downwind with infrared satellite sounders. Their measurements can also be used to derive physical parameters, such as optical depths and effective radii. However, one of the key requirements for accurate retrievals is a good knowledge of the complex refractive index (CRI) of the ash under investigation. In the past, the vast majority of the studies used the CRIs from Pollack et al. [Icarus19, 372 (1973)ICRSA50019-103510.1016/0019-1035(73)90115-2], which are based on measurements of thin slices of volcanic rock, and therefore are not representative for airborne volcanic ash particles. Here, we report measurements of the CRI of volcanic ash in suspension, generated from samples collected from recent high-impact eruptions in Chile (Puyehue-Cordón Caulle, Calbuco, and Chaitén), Iceland (Eyjafjallajökull and Grímsvötn), and Italy (Etna). The samples cover a wide range of ${{\rm SiO}_2}$SiO2 content (46% to 76%) as confirmed by an X-ray fluorescence analysis. In the experimental setup, volcanic ash was suspended in nitrogen through mechanical agitation. Extinction spectra were recorded in the infrared, visible, and ultraviolet spectral regions. The particle size distribution within the airflow was also recorded. An iterative algorithm allowed us to obtain fully consistent CRIs for the six samples, compatible with the observed extinction spectra and the Kramers-Krönig relations. While a good agreement is found with other recently reported CRIs in the UV/Vis, larger differences are found in the longwave infrared spectral region.
