2004 Fiscal Year Final Research Report Summary
Evolution of layered convection system and mantle dynamics
| Project/Area Number |
14340129
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体地球物理学
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| Research Institution | The University of Tokyo |
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Principal Investigator |
KURITA Kei The University of Tokyo, Earthquake Research Institute, Professor, 地震研究所, 教授 (00111451)
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| Project Period (FY) |
2002 – 2004
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| Keywords | mantle / tomography / convection / plume / temperature measurement / PIV |
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| Research Abstract |
The dynamics of mantle is driven by heterogeneity of temperature and composition. The region of higher temperature gains thermal buoyancy and the region with high Fe content gains negative buoyancy. The dynamics of the Earth's mantle is characterized by thermo-chemical convection system. In this research interaction of thermal convection with density-stratified layered structure has been investigated. Density-stratified layered structure is one of the typical situation of heterogeneity of chemical composition.
Laboratory fluid experiments are conducted to pursue this subject. Localized heat source at the base of fluid layer generates thermal plume, which interacts with the layered structure. We investigated various modes of interaction. Since the chemical composition and the temperature are two important factors we developed reliable measurement system for these two parameters. Te simultaneous measurement syst for velocity field(PIV), temperature field(microcapsule of TLC) and compositional field(LIF) are successfully constructed. Three major experimental series are analyzed by this research grant ; 1) Interaction of thermal plume with layered structure during ascent, 2)formation of plume in layerd structure, and 3)thermal instability of sedimentating system.
Particularly in the formation of plume in layered system several new phenomena have been clarified. Depending on the nature of the layered structure (ex. Density contrast and thickness of the base layer) three types of plume are found. ; successful plume, decoupled plume and failed plume. In the Earth's mantle the nature of the layered structure favors formation of failed plume. The failed plume is important in the interpretation of seismic tomography data because it would shed light on our overlooking at the chemical nature of the plume.
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