Summary in seconds: The Great Unconformity may have begun forming much earlier than the Snowball Earth glaciations, with major erosion occurring between about 2.1 and 1.6 billion years ago. This evidence challenges the traditional picture of the “Boring Billion” as a relatively quiet period in Earth’s history and complicates the idea that erosion directly helped trigger the Cambrian explosion. However, the findings are based on evidence from a limited number of sites in northern China, and scientists continue to debate how widely they can be applied. The Great Unconformity may therefore represent not one catastrophic event, but a long and