Vincenzo Nesi , Oscar Bruno , Davide Zaccagnino , Corrado Mascia , Carlo Doglioni
{"title":"岩石圈的潮汐拖曳和向西漂移","authors":"Vincenzo Nesi , Oscar Bruno , Davide Zaccagnino , Corrado Mascia , Carlo Doglioni","doi":"10.1016/j.gsf.2023.101623","DOIUrl":null,"url":null,"abstract":"<div><p>Tidal forces are generally neglected in the discussion about the mechanisms driving plate tectonics despite a worldwide geodynamic asymmetry also observed at subduction and rift zones. The tidal drag could theoretically explain the westerly shift of the lithosphere relative to the underlying mantle. Notwithstanding, viscosity in the asthenosphere is apparently too high to allow mechanical decoupling produced by tidal forces. Here, we propose a model for global scale geodynamics accompanied by numerical simulations of the tidal interaction of the Earth with the Moon and the Sun. We provide for the first time a theoretical proof that the tidal drag can produce a westerly motion of the lithosphere, also compatible with the slowing of the Earth’s rotational spin. Our results suggest a westerly rotation of the lithosphere with a lower bound of <span><math><mrow><mi>ω</mi><mo>≈</mo><mo>(</mo><mn>0.1</mn><mo>-</mo><mn>0.2</mn><mo>)</mo><mi>°</mi></mrow></math></span>/Myr in the presence of a basal effective shear viscosity <span><math><mrow><mi>η</mi><mo>≈</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>16</mn></mrow></msup></mrow></math></span> Pa<span><math><mrow><mo>·</mo></mrow></math></span>s, but it may rise to <span><math><mrow><mi>ω</mi><mo>></mo><mn>1</mn><mi>°</mi></mrow></math></span>/Myr with a viscosity of <span><math><mrow><mi>η</mi><mspace></mspace><mi>≲</mi><mspace></mspace><mn>3</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>14</mn></mrow></msup></mrow></math></span> Pa<span><math><mrow><mo>·</mo></mrow></math></span>s within the Low-Velocity Zone (LVZ) atop the asthenosphere. This faster velocity would be more compatible with the mainstream of plate motion and the global asymmetry at plate boundaries. Based on these computations, we suggest that the super-adiabatic asthenosphere, being vigorously convecting, may further reduce the viscous coupling within the LVZ. Therefore, the combination of solid Earth tides, ultra-low viscosity LVZ and asthenospheric polarized small-scale convection may mechanically satisfy the large-scale decoupling of the lithosphere relative to the underlying mantle. Relative plate motions are explained because of lateral viscosity heterogeneities at the base of the lithosphere, which determine variable lithosphere-asthenosphere decoupling and plate interactions, hence plate tectonics.</p></div>","PeriodicalId":12711,"journal":{"name":"Geoscience frontiers","volume":null,"pages":null},"PeriodicalIF":8.5000,"publicationDate":"2023-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"3","resultStr":"{\"title\":\"Tidal drag and westward drift of the lithosphere\",\"authors\":\"Vincenzo Nesi , Oscar Bruno , Davide Zaccagnino , Corrado Mascia , Carlo Doglioni\",\"doi\":\"10.1016/j.gsf.2023.101623\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>Tidal forces are generally neglected in the discussion about the mechanisms driving plate tectonics despite a worldwide geodynamic asymmetry also observed at subduction and rift zones. The tidal drag could theoretically explain the westerly shift of the lithosphere relative to the underlying mantle. Notwithstanding, viscosity in the asthenosphere is apparently too high to allow mechanical decoupling produced by tidal forces. Here, we propose a model for global scale geodynamics accompanied by numerical simulations of the tidal interaction of the Earth with the Moon and the Sun. We provide for the first time a theoretical proof that the tidal drag can produce a westerly motion of the lithosphere, also compatible with the slowing of the Earth’s rotational spin. Our results suggest a westerly rotation of the lithosphere with a lower bound of <span><math><mrow><mi>ω</mi><mo>≈</mo><mo>(</mo><mn>0.1</mn><mo>-</mo><mn>0.2</mn><mo>)</mo><mi>°</mi></mrow></math></span>/Myr in the presence of a basal effective shear viscosity <span><math><mrow><mi>η</mi><mo>≈</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>16</mn></mrow></msup></mrow></math></span> Pa<span><math><mrow><mo>·</mo></mrow></math></span>s, but it may rise to <span><math><mrow><mi>ω</mi><mo>></mo><mn>1</mn><mi>°</mi></mrow></math></span>/Myr with a viscosity of <span><math><mrow><mi>η</mi><mspace></mspace><mi>≲</mi><mspace></mspace><mn>3</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>14</mn></mrow></msup></mrow></math></span> Pa<span><math><mrow><mo>·</mo></mrow></math></span>s within the Low-Velocity Zone (LVZ) atop the asthenosphere. This faster velocity would be more compatible with the mainstream of plate motion and the global asymmetry at plate boundaries. Based on these computations, we suggest that the super-adiabatic asthenosphere, being vigorously convecting, may further reduce the viscous coupling within the LVZ. Therefore, the combination of solid Earth tides, ultra-low viscosity LVZ and asthenospheric polarized small-scale convection may mechanically satisfy the large-scale decoupling of the lithosphere relative to the underlying mantle. Relative plate motions are explained because of lateral viscosity heterogeneities at the base of the lithosphere, which determine variable lithosphere-asthenosphere decoupling and plate interactions, hence plate tectonics.</p></div>\",\"PeriodicalId\":12711,\"journal\":{\"name\":\"Geoscience frontiers\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":8.5000,\"publicationDate\":\"2023-04-27\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"3\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Geoscience frontiers\",\"FirstCategoryId\":\"1089\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S1674987123000907\",\"RegionNum\":1,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"GEOSCIENCES, MULTIDISCIPLINARY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geoscience frontiers","FirstCategoryId":"1089","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1674987123000907","RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
Tidal forces are generally neglected in the discussion about the mechanisms driving plate tectonics despite a worldwide geodynamic asymmetry also observed at subduction and rift zones. The tidal drag could theoretically explain the westerly shift of the lithosphere relative to the underlying mantle. Notwithstanding, viscosity in the asthenosphere is apparently too high to allow mechanical decoupling produced by tidal forces. Here, we propose a model for global scale geodynamics accompanied by numerical simulations of the tidal interaction of the Earth with the Moon and the Sun. We provide for the first time a theoretical proof that the tidal drag can produce a westerly motion of the lithosphere, also compatible with the slowing of the Earth’s rotational spin. Our results suggest a westerly rotation of the lithosphere with a lower bound of /Myr in the presence of a basal effective shear viscosity Pas, but it may rise to /Myr with a viscosity of Pas within the Low-Velocity Zone (LVZ) atop the asthenosphere. This faster velocity would be more compatible with the mainstream of plate motion and the global asymmetry at plate boundaries. Based on these computations, we suggest that the super-adiabatic asthenosphere, being vigorously convecting, may further reduce the viscous coupling within the LVZ. Therefore, the combination of solid Earth tides, ultra-low viscosity LVZ and asthenospheric polarized small-scale convection may mechanically satisfy the large-scale decoupling of the lithosphere relative to the underlying mantle. Relative plate motions are explained because of lateral viscosity heterogeneities at the base of the lithosphere, which determine variable lithosphere-asthenosphere decoupling and plate interactions, hence plate tectonics.
Geoscience frontiersEarth and Planetary Sciences-General Earth and Planetary Sciences
CiteScore
17.80
自引率
3.40%
发文量
147
审稿时长
35 days
期刊介绍:
Geoscience Frontiers (GSF) is the Journal of China University of Geosciences (Beijing) and Peking University. It publishes peer-reviewed research articles and reviews in interdisciplinary fields of Earth and Planetary Sciences. GSF covers various research areas including petrology and geochemistry, lithospheric architecture and mantle dynamics, global tectonics, economic geology and fuel exploration, geophysics, stratigraphy and paleontology, environmental and engineering geology, astrogeology, and the nexus of resources-energy-emissions-climate under Sustainable Development Goals. The journal aims to bridge innovative, provocative, and challenging concepts and models in these fields, providing insights on correlations and evolution.