Three‐dimensional numerical simulations of mantle flow beneath mid‐ocean ridges
Bibliographic record
Abstract
We perform three‐dimensional (3‐D) numerical simulations of an oceanic lithosphere cooling above a convective mantle to investigate mantle flow geometry and its associated lithospheric features. A constant horizontal velocity (half spreading velocity) of 2 (or 4) cm/yr is applied at the box surface to mimic plate motion. In all cases, because of the temperature‐dependent viscosity, a rigid conductive lithosphere cools progressively beneath the two plates separated by the ridge. After 16–40 Ma, cold downgoing instabilities develop at the base of the lithosphere. Small‐scale convection is then superimposed on the large‐scale circulation. It produces, and then interacts with, a slowly evolving short‐wavelength isotherms topography at the base of the lithosphere. The influence of the imposed ridge geometry on the mantle flow appears by comparison of simulations with case A, a linear ridge perpendicular to the plate motion; case B, a linear ridge strongly oblique to the plate motion; and case C, a ridge with transform faults along the spreading center with a mean orientation strongly oblique to the plate motion. All simulations reveal complex interaction between the isotherm topography within the base of the lithosphere, the small‐scale flow generated at or just below the base of the lithosphere, and the large‐scale flow dominating in the mantle below. The large‐scale flow appears always controlled by the mean ridge axis direction and thus may be oblique to the imposed plate motion direction. It is enhanced by the instabilities development. We argue that the large‐scale flow orientation results from the interaction with the small‐scale velocity field which flows down the isotherm topography at the base of the lithosphere. The latter is either inherited (lithospheric cooling, transform faults) or develops as boundary layer instabilities.
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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 | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".