Volcanic Geology And Secondary Volcanic Hazards In The Changbaishan-tianchi Volcano And Its Adjacent Areas

Volcanic eruption is not only one of the most spectacular scenes in nature,but also a manifestation of the strong motion of the earth's crust.Magmatic activities and geological phenomena associated with volcanic eruption are the foothold of volcanic geological research,involving the whole process of magma flowing from the depths of the underground to the surface of the eruption and accumulation.However,the eruption of volcanic eruptions must not be separated from the occurrence of secondary volcanic hazards,which are usually accompanied by volcanic eruptions,but can also be caused by the external cause of the products after the eruption of volcanoes.Comparing the volcanic geological characteristics with secondary volcanic hazards,studying the correlation between them has certain practical significance for hazard prevention and reduction.Changbaishan-Tianchi volcano and its adjacent areas are not only the accumulation area of volcanic lavas,pyroclastic lavas and volcanic debris,but also the high incidence areas of secondary volcanic hazards.As the most dangerous active volcano in China,Changbaishan-Tianchi volcano,the top of the volcanic cone is Tianchi,which is the birthplace of the Songhua River,the Yalu River and the Tumen River.Its stability has a great influence on the natural environment and human production and life in the surrounding area.Its own stratigraphic structure and the tectonic environment are likely to trigger a large scale secondary volcanic hazard.Therefore,based on the volcanic geological features of Changbaishan-Tianchi volcano and its adjacent areas,this paper analyses the types,characteristics and distribution of secondary volcanic hazards,based on the regional geological mapping and the distribution map of secondary volcanic hazards in Changbaishan-Tianchi volcano and its adjacent areas,combined with volcanic eruption and stratigraphic lithology,topography and geomorphology,geological structure,water and human activities.The purpose of this paper is to provide some scientific basis for hazard reduction and hazard prevention and government decision-making.The landslides are mainly distributed in basalt,rough rock,alkali fluid rock,andesite,clastic rock,metamorphic rock,granite,shale,limestone and marl.The landslides are mainly distributed in basalt and coarse rock formations,small in andesite and clastic rocks.The main source of the volcanic debris flow is basalt and coarse rock debris,as well as the eruption of volcanic eruption.After the erosion and destruction of the usually weak lithologic layer or the poor cementing diagenesis,it is transported and accumulated in the gully zone or in the gentle terrain.Changbaishan-Tianchi volcano and its adjacent areas above 1500 m altitude is the main body of Tianchi volcanic cone,which belongs to the lava mountain geomorphology,the terrain is undulating,the "V" or "U" valley is developed,the slope of the two sides of the river valley is large,some near vertical,the vertical height of the slope is up to 585 m,the slope below 50° is the main occurrence area of the landslide,and the slope of the slope is more than 50° generally collapse.The hazards,in the near and South Zone of the Wang Tian'e volcano,is a lava plateau,the river network is dense and the river valley is deep,forming a large number of "V" type valleys,and is also a frequent area of landslide and landslide hazards.The landform of the lava platform is below 1500 m.It is distributed in the north and northwest of the Tianchi volcano,and the Wang Tian'e volcano is upward in the west,and the microgeomorphology is more steep and prone to landslide.However,under 1000 m,the terrain began to slow down.The volcanic debris flow was formed in the undulating terrain and deep valley,moving rapidly in the steep slopes and narrow valleys.There are many faults in Changbaishan-Tianchi volcano and its adjacent areas,compared with the distribution of fracture and the location of secondary volcanic hazards,and most of the collapse and landslide hazardss occur in the vicinity of the fault.The complexity of regional tectonics and the increasing frequency of volcanic earthquakes,especially the spatial distribution of volcanic earthquakes in the region,coincide with the distribution of the current landslides and landslides.The primary columnar joint of volcanic lava in the area is developed.Under the influence of fracture structure and volcanic activity,the coarse rock or basalt rock formed by the columnar joints is squeezed and broken along the fracture surface under the stress action,causing the collapse and landslide hazards.In addition,the volcanic lava and the underlying rock layer are sandwiched with a thick layer of complex sand and gravel and Sargent soft layer,which make it unstable.Once it is peristated by the external force,the overlying rock will collapse or slide.At the same time,the collapse or landslide of rock mass provides a good material source for the formation of volcanic debris flow.Under the action of rainwater erosion and freezing and thawing,rock masses which are developed by primary joints and structural fractures are likely to be fragmented,resulting in rock collapse or rock slide.The natural stability of the mountain,the destruction of the vegetation,the serious erosion of soil and water are destroyed,and the collapse,landslide and the volcanic debris flow are easily caused in the harsh climate conditions.Due to the characteristics of sudden,recurrent and extremely strong destructive power,the hazard should be paid enough attention,take the necessary prevention and control measures in time.