Ultra-slow transverse waves during continental extension: A numerical model of the rift-drift transition
Bibliographic record
Abstract
Continental rifting is one of the four fundamental geological processes of the Wilson cycle. Rifting results from the continuous stretching of a continental mass and involves mechanical, thermodynamic, and rheological processes. It may last several tens Myrs and be followed by a catastrophic breakup stage (drifting), which determines cessation of continuous deformation and the final separation of a continent into two distinct tectonic plates that grow by accretion of oceanic lithosphere. To date, the transition to sea-floor spreading and the conditions for the development of a new ocean have not been fully understood. We present numerical experiments showing that a nonlinear viscoelastic model of the cratonic lithosphere, allowing accumulation of elastic strain over several Myrs, may explain the major features of the rift-drift transition. The model incorporates thermodynamic effects associated with viscous shearing, showing how thermal anomalies generated in the lithosphere during rifting play a major role in the break-up style. A fundamental result of the experiments is that extension is always accompanied by transverse material waves in the lithosphere, with wavelengths of the order of thousands km and periods of several tens kyrs. These waves induce an oscillating topography and could be responsible for high−frequency transgressive–regressive cycles in rift lakes. At sufficiently high extension rates, deformation localizes and these ultra-slow waves determine cyclic shear failure, with formation of X-shaped cross structures through the lithosphere that prelude to the final rupture. A comparison with the Red Sea evolution shows that onset of extension could be older than the widely accepted age of 27-30 Ma and that an older phase of uniform stretching without localization could have preceded the formation of a rift valley.
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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 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 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".