|Title||The influence of deep water cycling on plate tectonic transitions and the thermal histories of the Earth and rocky planets|
|Author||Fuentes, J; Crowley, J W; Mitrovica, J X|
|Source||American Geophysical Union Fall Meeting 2019, abstracts; DI43A-0031, 2019 p. 1 Open Access|
|Links||Online - En ligne|
|Alt Series||Natural Resources Canada, Contribution Series 20190252|
|Publisher||American Geophysical Union|
|Meeting||American Geophysical Union Fall Meeting 2019; San Francisco, CA; US; December 9-13, 2019|
|File format||html; pdf|
|Subjects||tectonics; extraterrestrial geology; Nature and Environment; Science and Technology; plate tectonics; thermal history; mantle; viscosity; convection; mid-ocean ridges; subduction zones; tectonic
setting; stress analyses; plate motions; models; thermal analyses; temperature|
|Program||Canadian Geodetic Survey Geodetic Analysis and Development - Gravity and heights systems|
|Released||2019 12 01|
|Abstract||Deep water cycling has been shown to have a strong influence on mantle dynamics in both numerical and analytic studies (e.g. Sandu et al., 2011, Nakagawa et al., 2015). Small increases in mantle water
content can significantly reduce mantle viscosity and thus have a strong influence on the style of plate tectonics and the thermal evolution of the mantle. In this study, we investigate the influence of mantle water cycling on the thermal history of
the Earth using the analytical mantle convection model of Crowley and O'Connell (2012) with degassing occurring at ocean ridges and regassing at subduction zones. Previous analytic models that investigate water cycling in the mantle often assume a
constant scaling between the Nusselt number and the Rayleigh number, implying a constant style of plate tectonics (e.g. Sandu et al. 2011, Crowley et al., 2011, Seales and Lenardic, 2017). In contrast, the model we have developed allows for natural
transitions between sluggish- and active-lid plate tectonics. Both styles are forms of mobile-lid plate tectonics; however, active-lid tectonics refers to the case where the plate is driven by stresses at the plate-mantle boundary and plate speed
scales with mantle temperature, while in the sluggish-lid case the plate is driven by local internal body forces, and plate speeds tend to be much smaller than mantle speeds. The model is run forward in time from 4 Ga to present using a wide range of
realistic mantle and lithospheric parameters. Results show that active-lid tectonics acts to regulate the mantle temperature and water content such that the initial values have little influence over the final values. In contrast, sluggish-lid
tectonics is very sensitive to the starting conditions. Furthermore, the initial water content and temperature have a strong control on the initial tectonic state and whether transitions will occur between states. |
|Summary||(Plain Language Summary, not published)|
This study explores how the movement of water in the Earth's deep mantle affects the way our planet's interior works. Researchers used a mathematical
model to simulate how water circulates in the mantle and influences the Earth's history over billions of years.
They focused on two types of plate tectonics: active-lid and sluggish-lid. Active-lid tectonics involve plates moving due to stresses
at their boundaries, while sluggish-lid tectonics result from internal forces, making the plates move more slowly.
The study revealed that active-lid tectonics help regulate the mantle's temperature and water content, so the starting conditions
don't have a big impact on the final state. In contrast, sluggish-lid tectonics are very sensitive to the initial conditions. The amount of water and the temperature at the beginning play a significant role in determining the type of tectonics and if
transitions between them occur.
The scientific impact lies in our understanding of how water in the deep Earth affects the movement of tectonic plates. This knowledge can help us comprehend the planet's geological history and how it continues to
change. It's important because it sheds light on the processes that shape our world, influencing everything from earthquakes to the formation of continents.