Fractal Properties And Their Geneses Of Lava Flows Of Laoheishan Volcano, Wudalianchi

Volcanism is a basic geological process. It shapes the earth's landscapes and contributes to its evolution and magmatic differentiation. Much work has gone into unraveling the eruptive mechanism by studying the products of volcanism in the past. This research emphasizes on the fractal properties of Laoheishan lava flows in Wudalianchi area.Through field observation and measurement of Laoheishan lava flows, we find that the area has various lava landforms. There are two main types of lava flows (a'a lava flow and pahoehoe lava flow). The margins of pahoehoe lava flows are more irregular than a'a lava flows, and the margins of a'a lava flows are straighter. The profiles of lava flow show the characteristics of layered distribution of vesicles. The closer to the top of lava flows, the more and bigger vesicle distribution and the more obvious deformation. The closer to the inner parts of lava flows, the smaller vesicles and the less obvious deformation.Utilizing the data of GPS measurements of the boundaries of lava flows and the digital photos, we calculate the fractal dimensions of boundaries of Laoheishan lava flows, and the fractal dimensions of vesicles in the lava profiles. The results show that the boundaries of lava flows and the vesicles are statistically fractal. The margins of lava flows and the vesicles are fractal in the definite scales. The higher fractal dimensions, the more irregular lava margins. The lower fractal dimensions of the characteristics of vesicles, the closer to the top of lava flows, the bigger vesicles and the more obvious deformation of vesicles. The calculated fractal dimensions of five boundaries of lava flows are respectively 1.040, 1.100, 1.110, 1.135 and 1.289. The fractal dimensions of vesicles in the twenty-six profiles of lava flows are the range from 1.22 to 1.68. The type of fractal characteristics of boundaries of lava flows is suitable to the finite scale of 5-80 meters.The fractal properties of boundaries of lava flows suggests that nonlinear processes are operating during the emplacements of lava flows because linear equations cannot produce fractals. The boundaries of high fractal dimension values are related to the low viscosities of lava, and the fractal dimensions of vesicles are related to the internal shear stresses in the lava flows.