Reference · the cadence, rung by rung
Eight rungs, checked
Eight collapses of the Earth's magnetic field, six thousand years apart, all the way down. Even spacing reads as a metronome, so the spacing is the thing to check. Each rung, against the palaeomagnetic literature.
The list being tested
What the card says, and what the literature holds.
From the "Disaster Cycle" presentation: forty-eight, forty-two, thirty-six, thirty, twenty-four, eighteen, twelve, six, now.
| Rung | Standing | What the literature holds |
|---|---|---|
| 48,000 y.a. Laschamp 1 |
Unsupported | No excursion is proposed at this age by anyone. The nearest either side are Laschamp at about 41,000 years and the Norwegian-Greenland Sea at about 60,000 to 64,000. |
| 42,000 y.a. Laschamp 2 |
Known | The strongest rung by a distance: the single Laschamp event, 42,200 to 41,500 years, in lava and sediment on every continent, and the tie point everyone else dates against. The field fell by as much as 90 per cent. |
| 36,000 y.a. Mono Lake |
Known Disputed | In the accepted inventory, and recovered as far off as Drake Passage sediments in 2025, though it sits nearer 34,000 years. The argument is over its own type locality: one line of work reads the Wilson Creek record as Laschamp misdated, with ages there running 30,000 to 41,000 by method. |
| 30,000 y.a. Michoacan |
Unsupported | No excursion of this name appears in the palaeomagnetic literature, confirmed or postulated. The burden sits with whoever put the name on the ladder. |
| 24,000 y.a. Lake Mungo |
Disputed | A much-cited study: magnetic directions from Aboriginal fireplaces and oven stones along the old shoreline in south-western New South Wales, departing by up to 120 degrees, with a second episode near 26,000 radiocarbon years. Follow-up work modelled it as a local source in the core, and it stayed on the postulated list. |
| 18,000 y.a. Hilina Pali |
Disputed | The most alive of the unconfirmed rungs. Ukrainian loess published in 2018 as a possible record drew a formal Comment accusing it of reinforcement syndrome, plus a Reply. Black Sea and Drake Passage records found nothing. Polar Urals lake cores recorded a distinct event near 20,000 years and are being worked on now. |
| 12,000 y.a. Gothenburg |
Disputed | Proposed from southern Scandinavia in 1977, claimed since in Barents Sea sediments, never accepted into the inventory. It is the rung the argument needs most, pairing with the Younger Dryas cold snap and the last claimed event, and the one unconfirmed longest. |
| 6,000 y.a. The "Noah" event |
Speculative | Offered as an inference, and stated as one: a green Sahara peak, volcanic evidence, and a dip in field strength whose datasets scatter between 4,500 and 7,500 years. Averaging datasets that disagree by three thousand years and treating the average as a dated event is the weak step. |
| Now Claimed to be under way |
Disputed | The field is weakening and the poles are moving, both measured. Whether that is an excursion beginning or an ordinary episode in a restless field cannot be told from inside it. |
That the shield has failed and recovered more than once is the settled part underneath the ladder, and it is argued on the claim.
The score
Two accepted, three postulated, two absent.
Most of the rungs are not invented. They are real proposed excursions, named by working palaeomagnetists, on a published list of events put forward and not yet accepted. There the dispute is confirmation, not existence.
A 2020 review holds seven proposals out of the inventory for the last 30,000 years, and its reasons are worth carrying fairly: remagnetised sediment, disturbed layers, changes in the material being deposited, and reinforcement syndrome, the habit of finding an excursion because you went looking for one.
Unconfirmed is not demonstrated absent. The 2025 study that found no Hilina Pali in Drake Passage sediments said so itself: the event may have been regional, or too short for those sediments to catch. The general rule is on the claim.
What takes the metronome away is the spacing, not the rungs
Count every excursion proposed for the last 30,000 years, including the unconfirmed ones the ladder relies on, and they land at roughly 2,700 years, 10,000, 12,000, 13,000, 19,000, 26,000 and 26,000. That is a scatter, with two almost on top of each other and a long gap where the ladder wants a rung. The events that fill the ladder and the events that break it sit at the same standard of proof.
Three of these rungs are live research, with people publishing against each other in the same journals this decade.
What would settle it → · The claim the ladder is offered as evidence for →