HR: 16:15h
AN: V14B-02 INVITED     [Abstracts]
TI: Fissure Eruptions Under Various Stress Conditions: Comparison Between Observations and Analog Experiments
AU: * Takada, A
EM: a-takada@aist.go.jp
AF: Geological Survey of Japan, HIgashi, Tsukuba, 305-8567 Japan
AB: Analog experiments for simple fissure eruptions of basaltic magma without volatile effects were investigated under various stress conditions. I prepared a 20-cm high gelatin block, injected silicon oil lighter than gelatin, and gave tensile stress and compressive stress under the displacement control by a jack. Fissure eruptions were observed from cracks filled with silicon oil in gelatin as elastic material. The degree of tensile stress makes eruptive fissure longer, and the volume ratio of intrusion to eruption lager. Relative height of eruption decreased with the degree of tensile condition. Next, temporal variations of eruption rate, height of eruption, and fissure length during an eruption were investigated using analog experiments. For example, the eruption rate decreases exponentially, which was supported by previous theoretical studies. Moreover, the case of open system makes the tail longer with various pulses. I compare the results on analog experiment with natural fissure eruptions. Fissure length, erupted volume, and activity duration are controlled by open or closed magma plumbing system, an initial volume and the local stress field. In the diagram of fissure length vs. erupted volume, fissure eruptions on rifts are plotted on the rift trend. Fissures of polygenetic volcanoes such as Izu-Oshima, Miyake, Hekla, Kilauea, Mauna Loa are in the wide range. In the diagram of fissure lengths vs. activity duration, fissure eruptions on rifts are plotted on the rift trend as those from a closed system,. Data from polygenetic volcanoes expanded in the range of open system. Those of Kilauea are expanded toward an open system eruption such as Puu Oo. Those of Mauna Loa, including NE rift and N fissure eruption, are expanded to the area of Open system. The erupted volume vs. activity duration diagram is distinguished flank eruptions from a closed system from central eruptions as open system.
UR: http://staff.aist.go.jp/a-takada/index-e.html
DE: 6063 Volcanism (5480, 8450)
DE: 8178 Tectonics and magmatism
DE: 8434 Magma migration and fragmentation
DE: 8439 Physics and chemistry of magma bodies
DE: 8445 Experimental volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005