南极洲乔治王岛柯林斯冰帽冰芯火山喷发记录

矿物和结构分析揭示了南极洲乔治王岛柯林斯冰帽一支 80 .2 m冰芯中的 9层深褐色沉积物的火山灰特征。本文从冰川处于稳定状态的假定出发 ,根据 Dansgaard- Johnsen流动模式断代结果 ,建立了南设得兰群岛火山喷发序列。依冰芯记录判断 ,该区 1 650年以来的 340年间 ,共有 7轮火山喷发。1 875～ 1 92 5年间似为火山活跃期 ,喷发地点可能主要在欺骗岛 ;1 650～ 1 80 0年间为一相对平静期 ;此后一个世纪不太稳定 ;而过去的 1 0 0年间基本平静 ,只是世纪初和 50～ 70年代间各有一段动荡期。冰芯中记载的大多数火山喷发可在该区有关文献中找到记录。没有记录在案的几例喷发事件需进一步调查。冰芯中缺失 1 967～ 1 970年欺骗岛火山灰层位表明 ,研究得到的火山序列仍未包含所有的喷发事件。但本文展示的该区过去 340年间火山活动基本趋势并不因此而改变。

VOLCANIC ERUPTIONS RECORDED IN AN ICE CORE FROM COLLINS ICE CAP,KING GEORGE ISLAND,ANTARCTICA

Careful mineral and structural analyses have revealed the characteristics of volcanic ash in the 9 horizons of a 80.2m ice core from Collins Ice Cap,King George Island,Antarctica. Under the assumption of steady state,Dansgaard Johnsen flow model was employed to date the core. The volcanic eruptive sequence established for South Shetland Islands region since A.D.1650 shows that 7 volcanic eruptive cycles could be distinguished during the past 340 years,as covered by the ice core. It seems that during the period of 1875-1925 there were frequent volcanic activities,with perhaps many eruptions at the Deception Island. The years between A.D.1650 to A.D.1800 appeared to be a quiet period,followed by an unsteady century in volcanic action. The past century is basically a tranquil era except for two turbulent epochs at the beginning of the century and in the 1950-70s. Many of the volcanic eruptions in the ice core sequence are found in the previously reported records for this region. A few of that are not in the records should be further investigated. The absence of 1967-1970 eruptive trace in the core suggests that the volcanic eruptions obtained by present study could still be the minimum number of the actual eruptions,although the general outline was exhibited by present study.