长白山天池火山造伊格尼姆岩喷发及气候效应

长白山天池火山属新生代多成因中央式火山。火山喷发活动经历了早更新世造盾喷发、中－晚更新世造锥喷发和近代造伊格尼姆岩喷发三个阶段。造伊格尼姆岩喷发时布里尼喷发柱高度曾达２５ｋｍ，伞状云顶部高度达３５ｋｍ。初始喷发温度为７８０℃，喷发速度３００ｍｓ－１。岩浆质量喷发率为１０８．３６ｋｇｓ－１，释放能量１．３４３６×１０１９Ｊ。喷发持续时间为四天半到十四天之间。高速流动的伊格尼姆岩最大流速１７０ｍｓ－１，流体前锋定位时仍保持了５０ｍｓ－１的运动速度。天池火山１２１５±１５Ａ．Ｄ．喷发物释放出了５×１０１０ｋｇ卤素元素和２×１０１０ｋｇ的Ｓ。喷发后导致了强烈的持续７年左右的“火山冬天效应”。在欧亚大陆中部地区最大降温幅度超过２．２５℃。

IGNIMBRITE FORMING ERUPTIONS FROM TIANCHI VOLCANO AND THEIR CLIMATE EFFECT

Tianchi volcano, located at the border of NE China and N Korea, is a Quarternary polygenetic central volcano. The eruptions are featured by a shield forming eruption, a composite cone forming eruption, and a ignimbrite forming eruption respectively. It is stated that the Plinian column once reached up to 25 km high with a initial temperature of 780 ℃ and velocity of 300 ms -1 of eruption, about a total energy of 1.3436×10 19 J had been released from the vent with a mass discharge rate of 10 8.36 kgs -1 which lasted for a time of 4～14 days. A maximum flowing velocity of the ignimbrite reached to 170ms -1 while around 50ms -1 setting velocity remained at the flow front. The ignimbrite forming eruption released 5×10 10 kg of F+Cl and 2×10 10 kg of S, which had left a serious “volcano winter” effect. That is, an average temperature decreasing of 1.5 ℃ happened on the north half hemisphere with a maximum transient temperature falling of 2.25℃ over the middle part of Eurasian continent.