Thermal evolution of Earth: Models with time‐dependent layering of mantle convection which satisfy the Urey ratio constraint
Bibliographic record
Abstract
We present a new set of Earth thermal history calculations in which the effect of increasing mantle layering with convection Rayleigh number is included in a parameterized mantle convection model. We demonstrate that the inclusion of this effect results in strong buffering of the upper mantle temperature and surface heat flow. Models of this type deliver the observed surface heat flow when geochemically constrained internal heating rates (Urey ratios) are assumed with reasonable initial core temperatures. The surface heat flow is also relatively unchanged for the last 3 Gyr of Earth history in models of this kind, in accord with geological inferences concerning ancient geotherms derived from the study of Archean continental materials. In contrast, models with constant degrees of layering spanning the range from whole mantle to fully layered convection are shown to require unreasonably high initial core temperatures in order to meet the surface heat flow constraint. All successful models require that the coupling of heat flow between reservoirs be smaller than would be expected if mantle viscosities are those inferred on the basis of postglacial rebound (PGR) observations. This may indicate that viscosity for convection is significantly greater than that for rebound and hence that mantle rheology is non‐Newtonian and that the PGR process is governed by transient rather than steady state creep.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 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".