Resolving a One-Year Ecesis Interval for Alaska Paper Birch: Dating a Rockfall Event, Wishbone Hill, Southcentral Alaska
Bibliographic record
Abstract
Numerous large boulders at the base of Wishbone Hill, northeast of Anchorage, Alaska, suggest a historic rockfall event and potential for future surface instability, putting lives and property at risk. The source of the rockfall-boulders is an exposed syncline with a cliff face composed of conglomerate. The age of trees growing atop boulders provides a minimum exposure-age of those boulders and, thus, the rockfall event. To determine when the rockfall occurred, we dated trees growing atop the boulders using tree-ring samples collected from 30 Alaska paper birch trees. After mounting and polishing, each tree-ring sample was dot-counted, and tree-ring widths were measured using Measure J2X software to generate a master chronology (1938-2017). To estimate the youngest age for the rockfall event, we recorded pith-year for each sample. For samples lacking a pith (n=21), we used pith indicators to match existing rings to diagrams of corresponding ring widths, projecting approximate pith for each sample. All samples we corrected for sampling height (mean=0.8m) using a low estimate growth rate (0.6m/yr). The oldest birch tree sampled included pith and, with height correction, we estimate a germination year of 1936. When using first-year growth as an event’s temporal marker, accounting for the ecesis interval, the time between the availability of a new surface (i.e., boulders) and germination provides a more representative date of the event than using the pith/germination date alone. Considering birch ecesis and primary observations recorded in 1935, we propose that the rockfall event most likely occurred in 1934-1935. This finding suggests an ecesis interval as low as one year for Alaska paper birch in fresh rockfall areas. The risk of another destabilizing event may prompt those utilizing this area for recreational and residential purposes to reconsider future use.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.002 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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; 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".