Today our planet is a lively place: the climate swings from greenhouse to icehouse and back again, while earthquakes, volcanoes, mountain ranges and ocean trenches are all signs of its restless surface. But if you go back far enough, you reach a period where Earth was a very dull place. Nicknamed the “Boring Billion”, the period between 1850m and 850m years ago appears to have had hardly any plate tectonic movement, very little change in climate and a stalling of biological evolution. But was this period more interesting than we think?
Geologists have been studying the geochemistry and makeup of continental rocks from the Boring Billion. The geochemistry suggests that the continental crust was hot and thin (40km or less) – not suitable for plate tectonics or building mountain ranges. But curiously the structure and composition of continental rocks indicate that crust did shimmy around and that low mountain ranges existed. The findings are published in Geophysical Research Letters.
Instead of the dodgem-car style of plate tectonics we have on Earth today, the Boring Billion seems to have been more like a waltz on a slippery dancefloor. This gentle form of plate tectonics has long since vanished, but understanding it may give us a clue as to how contemporary plate tectonics got started.
