774–775 carbon-14 spike
In 774–775 CE, tree rings show a sudden, worldwide spike in the radioactive carbon-14. The amount of carbon-14 rose about 1.2%, roughly 20 times the normal year-to-year change. This spike was found in Japanese cedar rings and dated by tree‑ring dating, and a similar signal appears in tree rings from Germany, Russia, the United States, Finland, and New Zealand, suggesting the event was global. Ice cores from Antarctica also show a spike in beryllium-10, another sign of a large burst of cosmic radiation at that time. The rise appears almost instantaneous and then slowly declined, pointing to a short, intense event.
The global production of carbon-14 for this event is estimated at about (1.3 ± 0.2) × 10^8 atoms per square centimeter. This 774–775 event is one of several known as Miyake events and is the largest and fastest 14C increase recorded in the last 11,000 years.
Scientists think the cause was a solar particle event from a very strong solar flare, rather than a gamma-ray burst, because the isotopic evidence includes 10Be and 36Cl, which fit a flux of charged particles hitting Earth and are concentrated toward the poles. Historical records around that time mention unusual sky phenomena, such as a “red crucifix” seen after sunset in some chronicles, but linking those tales to the carbon-14 spike is not certain.
The 774–775 spike is the strongest cosmogenic isotope event in the Holocene, with other notable spikes occurring later and earlier—such as around 993–994 CE and around 660 BCE, and a particularly strong one reported for 12,350–12,349 BCE. If a similar event happened today, it could disrupt modern technology and space navigation and pose radiation risks to astronauts.
Scientists still work to understand carbon-14 variations, because detailed, year-by-year records exist only for a few periods. For example, a 2017 study found a 2.0% rise around 5480 BCE, but that event’s cause doesn’t appear to be a solar flare.
This page was last edited on 3 February 2026, at 16:32 (CET).