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Viscosity jump in Earth's mid-mantle.
Maxwell L Rudolph1, Vedran Lekić2, Carolina Lithgow-Bertelloni3
1Department of Geology, Portland State University, Post Office Box 751, Portland, OR 97207, USA. maxwell.rudolph@pdx.edu.
Science (New York, N.Y.)
|December 15, 2015
Summary
Scientists found a significant increase in deep mantle viscosity between 800-1200 km depth. This discovery helps explain phenomena like stagnant tectonic plates and deflected mantle plumes.
Area of Science:
- Geophysics
- Earth Science
- Mantle Dynamics
Background:
- Deep mantle viscosity influences Earth's thermal evolution, plume dynamics, and material mixing.
- Understanding mantle layering is crucial for comprehending large-scale geological processes.
Purpose of the Study:
- To infer the viscous layering of Earth's deep mantle without prior assumptions.
- To investigate the relationship between viscosity variations and observed deep mantle structures.
Main Methods:
- Reanalysis of long-wavelength nonhydrostatic geoid data.
- Employing a novel method to determine viscosity variations with depth.
Main Results:
- Detected a substantial increase in mantle viscosity at depths of 800–1200 km.
- This viscosity increase occurs below the mantle transition zone.
- The depth of increased viscosity correlates with seismic observations of slab stagnation and plume deflection.
Conclusions:
- The inferred viscosity increase provides a unifying explanation for observed deep mantle phenomena.
- This finding challenges previous assumptions about mantle viscosity layering.
- Highlights the importance of viscosity structure in deep mantle dynamics.
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