Abstract:

Twenty types of volcanic materials ejected from Changbaishan volcanos were classified, such as columnar joint, pyroclastic flow deposits and lahars. Each of them can comprise a stratigraphic unit recognizable in the volcanic successions. Volcanic architectures are composed of these volcanic units bounded by some kind of eruption surfaces or unconformities. Monogenetic volcano fields, flood basalt field, lava shield volcanos, central volcanos and stratovolcanos described by Walker (2000) seem to develop successively from Miocene to Holocene in the area of Changbaishan volcanos. The potential volcanic hazards including both primary and secondary ones should be concerned there. The former indicates re-eruption of Changbaishan volcanos, which can not be predicted at the present but the giant water of 2×10⁹m³ contained in the Tianchi lake would trigger intensive phreatomagmatic eruptions and very large lahars in case of eruption some day. The secondary hazards would mainly come from large scale re-transportation of the pyroclastic deposits and rock slide-avalanche of the columnar joint basalts. Because the basaltic lavas are commonly situated on a soft sediment layer of ca. 3-7m which are composed of polymict gravel, sand, silt and mud. Differential subsidence of the basal sediments above the erosional surface of basement would easily cause the unstable volcanic architectures collapse. Geological survey on volcanic hazards and risk assessment are urgent task in the region of Chanbaishan volcanos.

Key words: volcanic rocks, volcanostratigraphy, volcanic architecture, physical volcanology, Changbaishan Tianchi volcanos, volcanic hazards of northeast China