Inferring Earth's discontinuous chemical layering from the 660-kilometer boundary topography.
basic_science · Level V
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- Record sourced from PubMed, PMID 30765566.
- Also identified by DOI 10.1126/science.aav0822.
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Abstract
Topography, or depth variation, of certain interfaces in the solid Earth can provide important insights into the dynamics of our planet interior. Although the intermediate- and long-range topographic variation of the 660-kilometer boundary between Earth's upper and lower mantle is well studied, small-scale measurements are far more challenging. We found a surprising amount of topography at short length scale along the 660-kilometer boundary in certain regions using scattered <i>P'P'</i> seismic waves. Our observations required chemical layering in regions with high short-scale roughness. By contrast, we did not see such small-scale topography along the 410-kilometer boundary in the upper mantle. Our findings support the concept of partially blocked or imperfect circulation between the upper and lower mantle.