Volcanic Hazard Assessment of Poás (Costa Rica) Based on the 1834, 1910, 1953–1955 and 2017 Historical Eruptions
Volcanic Hazard Assessment of Poás (Costa Rica) Based on the 1834, 1910, 1953–1955 and 2017 Historical Eruptions
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基于 1834 年、1910 年、1953-1955 年和 2017 年历史喷发的波阿斯（哥斯达黎加）火山危害评估
DOI：
10.1007/978-3-319-02156-0_11
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
C. Ramirez
中科院分区：
文献类型：
--
作者：
Raúl Alberto Mora Amador;D. Rouwet;G. González;P. Vargas;C. Ramirez
波罗·S是一座复杂的层状火山，海拔2708米，位于哥斯达黎加中部的科迪莱拉·沃尔卡尼察山脉。在2017年之前，最近三次历史性喷发发生在1834年2月7日、1910年1月至5月和1953-1955年期间。关于1834年喷发的信息很少。仅有的参考文献指出：这是一次重要事件；火山灰达到了宝岛-S西南偏西53公里处，并损害了火山周围的草原。这次喷发的相关沉积物表明，潜水活动发射了炸弹和积木。此外，火山口附近有火山碎屑流沉积的证据。1910年的火山喷发被描述得更好。尽管只有火山附近有火山灰坠落的报道，但据估计，矿床的体积为1.6亿×107m~3。喷发的沉积物呈白色，许多是热液改变的，并有少量的幼年碎片(泡状青金石)。火山喷发被归类为火山喷发，火山口附近有火山灰落下和火山碎屑流沉积。估计了火山爆炸性指数3(VEI 3)。火山喷发影响了农业。1953-1955年的喷发持续时间更长。据报道，在几个地点发现了各种火山灰沉降物。这次喷发的沉积物很容易在野外辨认出来，是黑色的蝎子状青金石，炸弹带有有时是纺锤形的面包皮结构。在火山口的东段，炸弹大小可达几米；一侧喷发中心附近的这种大炸弹表明喷发行为的倾斜度，即不对称的喷口-火山口系统。在火山口内，一个40米高的圆顶和一股熔岩流在喷发期间被挤出。在目前的拉古纳·卡连特火山口湖东侧，发现了一个8.5米厚的熔岩池的遗迹。在整个喷发过程中，酸湖大概缺少。据描述，这次喷发是一种混合型喷发：斯特龙博尔式喷发、云雾岩浆喷发、火山岩喷发和穹顶挤压喷发。考虑到这次喷发的特点、喷发柱的高度、喷射量(2.1m×107m~3)及其推定的持续时间，估计了VEI为3。火山喷发破坏了农业活动(包括牲畜)，迫使一些人自发疏散。2017年4月，在长达十年的强烈潜水活动期之后，岩浆喷发。这些喷发摧毁了1953-1955年的穹顶，并导致卡连特湖完全干涸。原火山口湖底表现为火山碎屑锥和硫磺火山作用。2017年的火山喷发严重影响了博鳌S及其附近的旅游活动，估计经济损失为2000万美元。到2018年5月至8月，卡连特拉古纳再次出现。与所研究的三次历史喷发有关的火山灾害是：火山碎屑流(距离喷发中心至少1公里，包括到达目前的米拉多尔扇区)、弹道(从发射中心向外抛掷炸弹，最多可达2公里)、火山碎屑的扩散和坠落(数十公里)、气体排放和酸雨，由西南风驱散，以及火山西南部大部分河谷的岩浆。
Poás is a complex stratovolcano with an altitude of 2,708 m a.s.l., located in the Cordillera Volcánica Central of Costa Rica. Prior to 2017, the last three historical eruptions occurred on 7th of February 1834, between January and May 1910 and during the period 1953–1955. Very few information exists on the 1834 eruption. The only references state that: it was an important event; ash reached >53 km W–SW of Poás, and it harmed the grasslands around the volcano. Related deposits of this eruption suggest phreatic activity, which launched bombs and blocks. Moreover, there is evidence of pyroclastic flow deposits near the crater. The 1910 eruption is better described. Despite the fact that ash fall is only reported near the volcano, a volume of the deposit of 1.6 × 107m3was estimated. Deposits of the eruption are white in color with many hydrothermally altered, and minor presence of juvenile fragments (vesicular lapilli). The eruption is classified as vulcanian, with deposits of ash fall and pyroclastic flows close to the crater. A Volcano Explosivity Index 3 (VEI 3) is estimated. The eruption affected agriculture. The 1953–1955 eruptions had a longer duration. Various ash fall deposits at several sites were reported. Deposits of this eruption, easily distinguished in the field, are black scoria lapilli, bombs with, sometimes fusiform, bread crust textures. In the eastern sector of the crater bombs can reach meters in size; such large bombs near the eruption centre at one side suggest the inclination of the eruptive conduct, or an asymmetrical vent-crater system. Inside the crater a 40 m-high dome and a lava flow were extruded during the eruption. Towards the eastern side of the current Laguna Caliente crater lake, relicts of a 8.5 m thick lava pool are found. During the entire eruptive episode, the acid lake presumably lacked. The eruption is described to be of a mixed type: strombolian, phreatomagmatic, vulcanian and dome extrusion eruptions. Considering the characteristics of this eruption, the height of the eruption column, ejected volume (2.1 × 107m3), and its presumed duration, a VEI 3 is estimated. The eruptions damaged agricultural activity (including cattle), and forced the spontaneous evacuation of some people. In April 2017 magmatic eruptions followed a decade-long period of intense phreatic activity. These eruptions destroyed the 1953–1955 Dome and led to the complete dry out of Laguna Caliente. Pyroclastic cones and sulfur volcanism manifested at the bottom of the former crater lake bottom. The 2017 eruption severely affected touristic activities at and near Poás, with an estimated economic loss of 20 million dollars. By May–August 2018 Laguna Caliente reappeared. The volcanic hazards related to the three studied historical eruptions are: pyroclastic flows (at least 1 km from the eruptive centre, including reaching the current mirador sector), ballistics (bomb ejections up to 2 km from the emission centre), dispersion and fall of pyroclasts (tens of kms), gas emission and acid rain, dispersed by WSW dominant winds, and lahars in most of the river canyons SW of the volcano.