Fern spike

In paleontology, a fern spike is the occurrence of abundant fern spores in the fossil record, usually immediately (in a geological sense) after an extinction event. The spikes are believed to represent a large, temporary increase in the number of ferns relative to other terrestrial plants after the extinction or thinning of the latter, probably because fern dispersal is more rapid over large geographic areas, since single-celled fern spores are more easily distributed by the wind than are seeds. Fern spikes are most associated with the Cretaceous–Paleogene extinction event, although they have been found at other events such as at the Triassic-Jurassic boundary. Away from the fossil record, fern spikes have also been observed to occur in response to local extinction events, for instance the 1980 Mount St. Helens eruption.