Photo: Early in our planet's history, volcanoes stopped spewing out lava for around 250 million years (Image: Denis Hallinan / Alamy)From New Scientist:
A 250-million-year shutdown of volcanic activity which is thought to have occurred early in Earth's history may be what turned the planet into a glacier-covered snowball. It could also have helped give rise to our oxygen-rich atmosphere.
Previous studies have noted that very little volcanic material has been dated to between 2.45 and 2.2 billion years ago, but it was widely assumed the gap would vanish as more samples were dated. Now an analysis of thousands of zircon minerals collected from all seven continents indicates that the gap may be real after all. Zircons provide a record of past volcanic activity, as the date they were formed can be calculated from the radioactive isotopes they contain.
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