YANSHAN AND GAOSHAN VOLCANOES IN THE DAXINGAN MOUNTAIN RANGE-A NEW ERUPTION STYLE

Yanshan and Gaoshan,two Holocene volcanoes in the Halaha River and Chaoer River volcanic cluster,are different from volcanoes with Strombolian eruption.Their early-stage eruptions produced pyroclasts which formed scoria cone,tephra fall-out sheet and small-scale pyroclastic flow,while the late stage eruptions effused a great amount of lava.They have large cones with the elevation above 200～300 meters,and the cones are made up of cinder cone and spatter cone.Tephra fall-out sheet is around the cones.The effused lava flow from the two volcanoes underwent the lava type transition from pahoeoe lava to aa lava.According to the characteristics of volcanic products,the eruption style is presented as follows:explosive eruption with a sustained eruption column,Strombolian eruption,lava fountain eruption.The sustained eruption column characterizes the new style and makes it different from typical Strombolian eruption.The similar eruption as Yanshan and Gaoshan happened in Longgang Quaternary volcanic cluster and Holocene volcanic cluster in Jingbohu.It is a new eruption style in the continental volcanism in China.