The turnover-pulse hypothesis, formulated by paleontologist Elisabeth Vrba, suggests that major changes to the climate or ecosystem often result in a period of rapid extinction and high turnover of new species (a "pulse") across multiple different lineages. Changes may include climate change, tectonic plate shifting, and catastrophes, among other things.[1] It can be seen as an extension of the concept of evolutionary radiation from a single to a multi-clade context.[2]