
NSF Org: |
EAR Division Of Earth Sciences |
Recipient: |
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Initial Amendment Date: | March 1, 2019 |
Latest Amendment Date: | July 6, 2020 |
Award Number: | 1853856 |
Award Instrument: | Continuing Grant |
Program Manager: |
Eva Zanzerkia
EAR Division Of Earth Sciences GEO Directorate for Geosciences |
Start Date: | March 15, 2019 |
End Date: | February 29, 2024 (Estimated) |
Total Intended Award Amount: | $375,000.00 |
Total Awarded Amount to Date: | $375,000.00 |
Funds Obligated to Date: |
FY 2020 = $260,000.00 |
History of Investigator: |
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Recipient Sponsored Research Office: |
110 INNER CAMPUS DR AUSTIN TX US 78712-1139 (512)471-6424 |
Sponsor Congressional District: |
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Primary Place of Performance: |
10100 Burnet Rd., ROC196 Austin TX US 78758-4445 |
Primary Place of
Performance Congressional District: |
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Unique Entity Identifier (UEI): |
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Parent UEI: |
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NSF Program(s): | Geophysics |
Primary Program Source: |
01002021DB NSF RESEARCH & RELATED ACTIVIT 01002122DB NSF RESEARCH & RELATED ACTIVIT |
Program Reference Code(s): |
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Program Element Code(s): |
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Award Agency Code: | 4900 |
Fund Agency Code: | 4900 |
Assistance Listing Number(s): | 47.050 |
ABSTRACT
Plate tectonics is fundamental for Earth's evolution and the surface expression of mantle convection. However, it is unclear how the narrow and strongly deforming boundaries between the more rigid plates form. The reactivation of plate boundaries, in particular, gives the continental plates a long-term hysteresis with profound implications for tectonics. This project seeks to better understand the causes and consequences of damage memory in convection. Funding will support a female graduate student and speak to issues outside geodynamics including the quest for a general law describing fault behavior from the seismic cycle to long-term Earth evolution. The project will also support new international collaborations, and research outcomes will be disseminated widely, including for UT Austin's GeoFORCE K-12 outreach program.
This project will implement strain-dependent weakening into global, numerical convection models in order to explore the style of "plate tectonics" that is generated by visco-plastic mantle flow. Incorporating such rheological memory will allow study of the full range of tectonic behavior, including how plate boundary evolution and plate motions are linked with the deep mantle. A range of viscous damage formulations will be explored and benchmarked against grain-size evolution theories and other suggested mechanisms for strain-localization, such as formation of shear bands and mechanical anisotropy due to lattice preferred orientation of olivine. Model results will be compared with geological constraints including plate kinematics, with particular focus on the time-dependence of plate boundary geometry, plate speeds and sizes, and seafloor age distributions. The overall goal is to develop a theoretical understanding of the role of tectonic inheritance in terrestrial planet evolution and heat transport.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
The Earth's surface geology records billions of years of tectonic activity where the plates on which we live are continuously reworked due to the effects of subduction and mantle plumes, the down and upwelling limbs of mantle convection, respectively. This project supported the development of new numerical methods and computational models that allowed for the study of the effects of the memory of deformation on rock behavior in regional and global planetary tectonics. Eight publications results so far on a range of topics within the realm of the interaction between mantle convection and surface tectonics. For example, we were able to show that ductile, creeping deformation memory is an important ingredient for the generation of plate tectonics from global, visco-plastic convection. The accumulation of damage appears to counteract a decrease in convective vigor over terrestrial planetary evolution. Preservation of ductile damage is enhanced once continental plates with inherently different preservation qualities are considered, and such, more complete, models can reproduce a range of observations from plate reconstructions as well as the deep record of tectonics, the internal structure of the Earth as inferred from mantle seismic tomography. If ductile damage is combined with brittle damage mechanisms, such as might be expected in the bending regions of the trench in subduction zones, a new phenomenon, plate segmentation or boudinage, arises. Such segmentation can explain a range of puzzling observations from subduction zones, such as large offset normal faults and lower plate localized low flow strength. Importantly, the segmentation phenomenon is emergent from the interactions between the two dynamical weakening mechanisms. This discovery is an example of the power of geodynamic models where new findings arise from theoretical analysis. We were also able to show that once damage is included, hot mantle plumes have more pronounced tectonic consequences than is typically thought. Those effects include the ability of plumes to potentially terminate subduction, in an interesting top to bottom to top interaction loop. The project supported the training of a graduate student in US STEM workforce relevant topics, and the student is now working as a researcher at a US national lab, applying her training in societally relevant fluid transport problems. The project also supported the training of a post-doc, who is now a researcher in academia.
Last Modified: 03/13/2024
Modified by: Thorsten W Becker
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