汤加王国洪加火山的前世今生  

The past and present activities of Tonga’s Hunga Volcano

作　　者：魏海泉[1] 陈正全[1] WEI Haiquan;CHEN Zhengquan(National Observation and Research Station of Jilin Changbaishan Volcano,Institute of Geology,China Earthquake Administration,Beijing,100029)

机构地区：[1]中国地震局地质研究所,吉林长白山火山国家野外科学观测研究站,北京100029

出　　处：《地质论评》2022年第5期1942-1954,共13页Geological Review

基　　金：国家自然科学基金青年基金项目(编号:41802252);中央级公益性科研院所基本科研业务专项(编号:GCEA1703)的成果。

摘　　要：洪加(Hunga)火山位于新西兰—克马德克—斐济俯冲带,该火山于2021年末又开始活动,并在2022年1月14、15日发生了千年一遇的世纪大喷发。喷发柱穿进平流层,形成了一个最高30 km、最宽800 km的蘑菇云,后期的气体火山灰云团几乎环绕南半球一周。喷发所引起的海啸在太平洋沿岸多地造成了灾害。根据现有的资料分析,洪加火山岩浆成分以安山岩为主,岩浆可能是沿着破火山口边缘由富气岩浆团块的“渗漏”驱动喷发的。这次洪加火山大喷发的一个最重要特征是喷发时产生了极为强烈的大气冲击波,这代表了岩浆内火山气体的极大富集。正是这种“超级富气岩浆”的喷发在喷火口位置形成了远超0.1 MPa(1标准大气压)的出口压强,引发了向全球辐射的冲击波和数千千米以外都能听到的喷发声响。本次火山喷发引发海啸的机制,其一是爆炸冲击波,向外扩张的冲击波推动了海面表层海水的向外扩张;其二是苏特塞式(Surtseyan)喷发本身就有向外排走海水的能力。未来洪加火山喷发形式,很可能是沿着破火山口周边断裂或靠近破火山口中央谷地的熔岩穹丘或熔岩流。苏特塞式喷发会比较常见,但喷发规模不会太大。The Hunga volcano,located in the New Zealand—Kermadek—Fiji subduction zone,reactived in late 2021 and had a millennium-scale centurial eruption on January 14 and 15,2022.The plume penetrated into the stratosphere,forming a plume with 30 km high and 800 km wide at top.The gas—ash cloud circled almost all around the southern hemisphere.The tsunami caused by this eruptive event brought damage in many places around the Pacific coast.According to the existing data the magma composition of Hunga volcano is mainly andesite,and the magma may be driven by the "leakage" of gas-rich magma masses along the edge of the caldera.One of the most important significances of the Hunga eruption is that it produced an extremely strong atmospheric shock wave,which implies a great enrichment of volcanic gases within the magma.It is this eruption of "super-rich gases" that creates an outlet pressure of well over one barometric pressure at the crater,triggering a shock wave that radiates across the globe and an eruptive sound that can be heard thousands of kilometers away.The tsunami was triggered by an outward spreading shock wave in the atmosphere,which pushed the surface water outward.Another mechanism for this tsunami is that Surtseyan eruptions have the ability to expel water outwards.Eruptions of Hunga in future are likely to take the form of lava domes or flows along the perimeter of the caldera rim or near the central depression of the caldera.Surtseyan eruptions are common,but not on a large scale.

关 键 词：海底火山 苏特塞式喷发 破火山口 富气岩浆 未来喷发 

分 类 号：P317[天文地球—固体地球物理学]