Crustal deformation induced by mantle dynamics: insights from models of gravitational lithosphere removal
Bibliographic record
Abstract
Mantle-based stresses have been proposed to explain the occurrence of deformation in the interior regions of continental plates, far from the effects of plate boundary processes. We examine how the gravitational removal of a dense mantle lithosphere root may induce deformation of the overlying crust. Simplified numerical models and a theoretical analysis are used to investigate the physical mechanisms for deformation and assess the surface expression of removal. Three behaviours are identified: (1) where the entire crust is strong, stresses from the downwelling mantle are efficiently transferred through the crust. There is little crustal deformation and removal is accompanied by surface subsidence and a negative free-air gravity anomaly. Surface uplift and increased free-air gravity occur after the dense root detaches. (2) If the mid-crust is weak, the dense root creates a lateral pressure gradient in the crust that drives Poiseuille flow in the weak layer. This induces crustal thickening, surface uplift and a minor free-air gravity anomaly above the root. (3) If the lower crust is weak, deformation occurs through pressure-driven Poiseuille flow and Couette flow due to basal shear. This can overthicken the crust, producing a topographic high and a negative free-air gravity anomaly above the root. In the latter two cases, surface uplift occurs prior to the removal of the mantle stress. The modeling results predict that syn-removal uplift will occur if the crustal viscosity is less than ∼1021 Pa s, corresponding to temperatures greater than ∼400–500 °C for a dry and felsic or wet and mafic composition, and ∼900 °C for a dry and mafic composition. If crustal temperatures are lower than this, lithosphere removal is marked by the formation of a basin. These results can explain the variety of surface expressions observed above areas of downwelling mantle. In addition, observations of the surface deflection may provide a way to constrain the vertical rheological structure of the crust.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 teacher head, 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".