Effect of lower mantle viscosity on the time‐dependence of plate velocities in three‐dimensional mantle convection models
Bibliographic record
Abstract
Earth's evolution has featured stages of relatively steady plate motion interrupted by brief periods of rapid change in plate direction. Previous studies have shown that vigorously convecting internally heated systems featuring dynamically determined plate‐like surface motion can also be characterized by predominantly steady periods punctuated by comparatively short reorganization events. Here, we investigate time‐dependence in two mantle convection models featuring significantly contrasting viscosity profiles and assess the influence of lower mantle viscosity on plate velocity time‐dependence. We model a system featuring nine finite thickness viscous plates at the top of a 6 × 6 × 1 Cartesian geometry solution domain. We find that plate reorganization events involving between 1 and 3 plates occur with geologically relevant frequency in a calculation featuring a factor of 36 increase in lower mantle viscosity relative to the upper mantle. Specifying a mantle viscosity at a depth of 2000 km that is 3000 times greater than the upper mantle viscosity suppresses this time‐dependence.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".