The Osmium Fingerprint: Visualisation · Signals from the Periphery

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THE FISSURE

Subject

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Value

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Verdict

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THE OSMIUM FINGERPRINT
Fissure eruption vs impact: who spiked the ice?
the sequel to INST-46's one surviving measurement
a 9 km ceiling, and a channel proven in 1783 and 1991
five osmium horizons where one impact should be
no crater on one side; no named vent on the other
pick an eruption · mix the endmembers · read the rows

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Evidence

fact ⇄ what kind of claim · live

Pt in GISP2 ice climbs ×100 to 82.2 ppt at 12,822 BP, over ~14 yr

Petaev 2013 · the one line both sides accept

MEASURED

Hekla 1991 wrote a Pt peak into Summit snow, 1,218 km away

Gabrielli 2008 · the channel, caught working, same metal, same site

MEASURED

Hall's Cave: five unradiogenic Os horizons across ~4,000 yr, Os enriched alone

Sun 2020, Table S1 in full · Ir, Ru, Pt, Pd stay crustal

MEASURED

Eight bipolar sulfate events 13,023-12,871 BP; V8 = 2× Okmok, 25 yr pre-onset

Abbott 2021 · synchronised Greenland + Antarctic cores

MEASURED

The Pt spike sits ~48 yr AFTER the Younger Dryas onset

Green 2025 · too late to be the trigger, whoever made it

MEASURED

The chondrite fraction fitting the Os over-predicts Ir ×250

computed here from Sun's table + CI abundances · the deciding row

MODELLED

Same-depth replicates disagree in BOTH camps' key tables; all drawn

171 cm: 0.12 vs 1.48 · PL 8.51 m: 0.51 vs 0.75 · undiscussed

REPORTED

"Volcanic" is a fingerprint, not a culprit: no vent has been named

no tephra shard in the Pt layer · the case stays open

READING

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The eruption

Discharge feeding the column2,000 m³/s

Not total lava output: Holuhraun poured 100 m³/s and fed its column almost nothing. Mastin 2009: H = 2.0 V^0.241. About 500 m³/s clears the 9 km ceiling.

Eruptionthe curtain plays

The ceilingsubpolar tropopause, ~9 km

Transport to Summitlights only above the ceiling

The mixture

Exotic fraction0.10%

Mass fraction of the selected endmember mixed into local crust. The marker walks the curve; the three rows re-judge every frame.

The record

Eruption ledgerAbbott 2021 sulfate strip

Labels

Readout · live

Column height

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Ceiling threshold

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Mixture (R · Os)

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Ir over-prediction

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P(5 impacts / 4 kyr)

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Pt lag after onset

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What is measured vs modelled here

Measured: both published tables in full (37 + 30 rows, replicate disagreements included), the GISP2 platinum series, the Abbott sulfate events, the Hekla 1991 Summit fallout, Laki's and Eldgjá's ice-core sulfate, and every eruption parameter chip. Reported: Laki's 800-1,400 m fountains (secondary sources only), Young's 153 cm sample (unpublished, both sides), the four-site YD-base comparison where Friedkin is paywalled. Modelled: the column height (Mastin), the two-component mixing, the Ir over-prediction, the recurrence probability. Reading: which suspect made the spike. The bench declines to answer that one.

The model, in full

Mixing is two-component conservation: R_mix = (f·C·R + (1−f)·Cc·Rc)/(f·C + (1−f)·Cc), with ¹⁸⁸Os taken proportional to total Os (error under 3% below R = 2.5). The chondrite test solves f against the sample's Os, then prices the Ir that fraction must deliver at CI proportions. The volcanic band is the envelope of Sun's four published curves, not a fit of ours. The column is H = 2.0·V^0.241 applied to column-feeding discharge, anchored on Laki (2,000 → 12.5 km, observed 9-13), Eldgjá (4,000 → 14.8, observed 11-18) and Holuhraun (3 → 2.6, observed under 4). P(≥5) is Poisson at the generous 100 kyr impact recurrence. All anchors in scripts/osmium-tune.mjs.

Where this drawing takes liberties

The fissure scene's fountains and plume are sprite impressions; their heights, and everything else in the scene, are at true 1-unit-per-km scale. The terrain relief, the twilight sky and the moon are scenery, though honest scenery: the plain by the fissure is flat because flood basalts pool, the ridges stay under real Icelandic relief, the ice cap is a Vatnajökull-class line about 100 km out, and the twilight is June at 64 degrees north, which is when Laki opened. The curtain's flicker is decoration. Sample-to-horizon grouping at Hall's Cave (UR1-UR5) is reconstructed from Sun's text, which never publishes an explicit mapping and never names the 155 cm horizon. Page-Ladson ages other than the dated YD base are stratum-level, so its record is drawn on depth, not age. Petaev's Pt/Ir claim is qualitative in the original and carried here without a number.

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