Hekla 3

So now Baxter has started on the Bronze Age Collapse. He's following Cline, 1177 B.C.: The Year Civilization Collapsed. Cline proposed that the Hekla 3 eruption did what the late AD 530s blowups would do, except to a less-resilient civilisational network. Cline relied on Baillie's date for the Hekla 3 eruption over in Iceland.

I never took Cline seriously. As for Baillie: when he ate a retraction about the 1645 BC volcano (Alaska, not Thera) I figured that Baillie might have been wrong about other stuff when, like all of us once were, he was young and excitable. Still, Stone Spring depends on that thesis; Baxter's world is more resilient than ours was. And the man is a normie. To the extent midwits stuff Internet comment-boards with Kewl Kuttin'-Edge Idears; Baxter will clutter the science-fiction shelves with that rubbish, too.

To some level the shift of water-mass away from Europe might deform the crust enough to change when, and how, Hekla went up. But that's a copout. Hekla 3 is a hoax. A "false-flag". Didn't happen; it is a meme.

So let's look in on this. After the Norse landing AD 870, our mountain blew up AD 1104 in a Plinian kaboom (creating a rhyolite) and then AD 1158 (dacite). Before known human habitation, absent the odd castaway or monk, geologists identify several layers: 3, ‐S, ‐4, ‐Ö, and -5. Because we aren't moles so dig from top to bottom, the higher layers bear the lower cardinality. H-4 was the worst at esplod'ity index (VEI) 5. The worst VEI elsewhere since we were Africans were the Kawakawa/Oruanui at Tia's Cloak (Taupō) and Toba at 8; Tambura and the more recent Taupō were 7. H-4 would rank with Vesuvius and Mt. St. H., at 5.

Sure, Iceland's incessant VEI 3-4 tephra is annoying for Brits and even for Finns. And as Laki proves, Iceland doesn't need a Plinian to mess up the northwestern Old World - a year of steady outgassing will do. But a Plinian is what Baillie was arguing: the H-3. For an Icelandic kaboom to bounce its ash over the Alps to affect the Eastern Mediterranean, I demand for VEI a 6 (Pinatubo) - at least. That was not H-4 and, as for H-3, which is what Baillie wants, that wasn't even a 5. Baxter illustrates, of course, Icelandic Vesuvius.

H-3 presaged "A shift in eruption mode of Hekla volcano", as Guðrún Larsen et al. wrote (doi 10.1002/jqs.3164). The mountain erupted more frequently but didn't gouge itself out, as H-4 had done. These flows made a literal mountain of what had been more like Thera, a flattish crater. One advantage of a more regular, moderate eruption cycle is that its layers are better for constraining when they happened.

Hekla‐D is found just above Katla‐E, which together come to 2940 years ago (¹⁴C 2790 ± 45 BP). Below / before K-E is H-O, which is more difficult to constrain... since it came soon enough after the big H-3 that some important metrics were distorted. We don't get tree-rings; Iceland ain't exactly known for its bountiful forests. (We'd thank the Vikings but, we're talking the Hekla and Katla belts.)

TL;DR - H-3 and then H-O should get treated together. Their dating is churned up. Consensus currently states that they happened very late 11th century. Consensus meanwhile pins the Bronze Age Collapse to Rameses III's forts ringing the Gaza / Ashqelon coast; that's usually set early 12th. (It helps we own a vita of this Rameses from his son's reign: the Harris Papyrus.) That presents a gap of, what, 150 years. And anyway H-3 was too weak to matter past the English British Channel, at a time when Britain itself was backward.