2013 Fiscal Year Final Research Report
Fragmentation mechanism of vesicular magma in soild/fluid transition resime
| Project/Area Number |
24656119
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| Research Category |
Grant-in-Aid for Challenging Exploratory Research
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| Allocation Type | Single-year Grants |
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| Research Field |
Fluid engineering
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| Research Institution | Tokyo University of Agriculture and Technology |
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Principal Investigator |
KAMEDA Masaharu 東京農工大学, 工学(系)研究科(研究院), 教授 (70262243)
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| Co-Investigator(Renkei-kenkyūsha) |
ICHIHARA Mie 東京大学, 地震研究所, 准教授 (00376625)
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| Project Period (FY) |
2012-04-01 – 2014-03-31
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| Keywords | 火山爆発 / 破砕 / 気泡 / 粘弾性 / き裂 |
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| Research Abstract |
Magma fragmentation is a key phenomenon controlling volcanic eruptions. The fragmentation of magma, which is a viscoelastic fluid, occurs through a combination of viscoelasticity and rapid deformation. We conducted a rapid decompression experiment to clarify the viscoelastic effect on the fragmentation using a magma analogue, syrup containing gas bubbles. We demonstrated the existence of a brittle-like fragmentation, which occurred even if the response of material should be in a ductile manner. Comparing the realistic decompression time with the viscoelastic relaxation time for magma, it is probable that the fragmentation in the real volcanic system occurs in a brittle-like manner.
Observation indicated that the onset of brittle-like fragmentation was triggered by the sudden release of a considerable amount of gas from a crack in the specimen. Further observation implies that the crack is initiated from the interior of the specimen due to non-uniform spatial distribution of bubbles.
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