A new item in the Proceedings of the National Academy of Sciences (PNAS) hypothesizes that the Late Devonian mass extincion was a result of a supernova.  It would need to have been much closer or more powerful than Kepler’s supernova of 1604 to destroy the ozone layer and kill much of Earth’s life, but not enough to wipe out the planet.  It’s comparable to being in the survival zone of a nuclear blast (e.g. 10km away from the bomb dropped on Hiroshima).

If the blast were a very short term event (i.e. a single burst lasting a few hours) and not prolonged, being on the far side of the planet might be enough to survive.  Africville was spared the brunt of the 1917 Halifax explosion because it was on the far side of a hill.

Supernova triggers for end-Devonian extinctions

PNAS first published August 18, 2020

Abstract

The Late Devonian was a protracted period of low speciation resulting in biodiversity decline, culminating in extinction events near the Devonian–Carboniferous boundary. Recent evidence indicates that the final extinction event may have coincided with a dramatic drop in stratospheric ozone, possibly due to a global temperature rise. Here we study an alternative possible cause for the postulated ozone drop: a nearby supernova explosion that could inflict damage by accelerating cosmic rays that can deliver ionizing radiation for up to ∼100∼100 ky. We therefore propose that the end-Devonian extinctions were triggered by supernova explosions at ∼20 pc∼20 pc, somewhat beyond the “kill distance” that would have precipitated a full mass extinction. Such nearby supernovae are likely due to core collapses of massive stars; these are concentrated in the thin Galactic disk where the Sun resides. Detecting either of the long-lived radioisotopes Sm146 or Pu244 in one or more end-Devonian extinction strata would confirm a supernova origin, point to the core-collapse explosion of a massive star, and probe supernova nucleosynthesis. Other possible tests of the supernova hypothesis are discussed.

This is testable.  If the right Samarium or Plutonium isotopes are found in the environment, it would back up the theory.  Cool.