Glass geochemical compositions from widespread tephras erupted over the last 200 years from Mount St. Helens
Bibliographic record
Abstract
ABSTRACT Building reliable chronologies from lake sediments, peat and other paleoenvironmental archives can be challenging, especially for historical times where radiocarbon is unreliable. Nineteenth‐ and 20th‐century eruptions from Mount St. Helens (MSH) provide important chronostratigraphic markers for regional paleoenvironmental studies within this time frame, but are constrained by poorly geochemically characterized tephra and/or limited published data. Here, we present glass geochemistry from the most significant eruptions from this time. This includes proximal, medial and distal deposits of the 18 May 1980 MSH eruption, layer T ( ad 1799/1800), a new tephra that we argue represents the ad 1842 eruption, and the 22 July 1980 eruption that had reported ashfall in Canada. Our results indicate that most tephras ejected during these eruptions, within a time frame of ~200 years, have distinct glass geochemical characteristics that can be used to identify distal deposits for tephrochronological studies. Layer T is on trend with analyses of the 1980 eruption but has a distinct dacitic glass population. The 1980 and ad 1842 eruptions are similar, both having rhyolitic glass compositions, but the ad 1842 event can be differentiated by a more constrained SiO 2 range in the main geochemical population, and the presence of a unique SiO 2 sub‐population.
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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; both teacher heads agree on what is shown here.
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".