An Extended Rheological Map of Pāhoehoe—‘A‘ā Transition
Bibliographic record
Abstract
Abstract The pāhoehoe—‘a‘ā morphological transition involves a change in the rheological response of the magmatic suspension from pure viscous to complex rheological behavior, resulting in the development of tear‐apart features. Here, we present a suite of concentric cylinder experiments aimed at studying the effects of cooling and shear rates on the rheology of a phonotephrite melt in response to crystallization. Experiments were conducted at: (a) isothermal subliquidus temperatures of 1,167–1,189°C and shear rates of 1–3 s −1 ; (b) constant cooling rates of 1–10°C/min and shear rates of 1–20 s −1 . We defined the viscosity‐temperature‐time window of lava solidification, as well as the transition from coherent flow to shear localization and physical separation (i.e., viscous rupture). Through this approach, we mapped the processes and timescales affecting pāhoehoe—‘a‘ā transition in natural lavas at variable cooling and shear rates. Under disequilibrium conditions, as the cooling rate increases, both crystallization onset and viscous rupture occur at lower temperature and earlier in time. Moreover, the time to reach the crystallization onset and viscous rupture also decreases with increasing shear rate. Both increasing cooling and shear rate reduces the critical crystallinity required for viscous rupture, a consequence of the non‐linear interplay between temperature, crystallization kinetics, and melt viscosity. This outcome expands our knowledge on compositional, thermal, and rheological changes in phonotephritic systems. In addition to shear rate and apparent viscosity, comparison with previous measurements on basaltic systems indicates that the pāhoehoe—‘a‘ā transition is sensitive to the composition and cooling path of lavas.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.011 | 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".