Influence of Upper Plate Structure on Flat‐Slab Depth: Numerical Modeling of Subduction Dynamics
Bibliographic record
Abstract
Abstract Western North and South America have been affected by flat‐slab subduction where a segment of the subducting plate becomes horizontal below the overlying continent. Modern observations and constraints on past geometries show that the depth of the flat‐slab varies from just below the continental Moho to >100 km depth. Thus, in some areas, there is little to no continental mantle lithosphere (CML) above the flat‐slab, whereas other flat‐slab areas are overlain by CML thicknesses >50 km. The mechanisms causing different slab depths are unclear. We examine flat‐slab subduction dynamics and slab depth through 2‐D thermal‐mechanical modeling. The models investigate plate structures and velocities similar to those of the Cretaceous western United States and present‐day South America. Models show that flat‐slab depth is primarily determined by continental structure. A deep flat‐slab occurs if the continent is initially thick, as its mantle lithosphere is cool and thus too strong to be displaced by the flat‐slab. The CML rheology plays a secondary role. A weak, hydrated lithosphere is easily displaced, leading to a shallower slab. The flat‐slab can displace up to 50% of the thickness of the CML, and no model exhibits displacement of the full CML thickness. This suggests that shallow flat‐slabs below Mexico and Peru require a thin continent prior to slab flattening. The models also show that a flat‐slab is deflected downward when it encounters thick craton lithosphere, with a larger depth for a chemically depleted craton. This has implications for modification of the Wyoming craton during Farallon flat‐slab subduction.
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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 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".