An Extraterrestrial Trigger for the Mid-Ordovician Ice Age

The mid-Ordovician field site used in the Schmitz et al. study. Image credit: Schmitz et al.,
Science Advances 2019

About 466 million years ago, in the middle of the Ordovician period, the L-chondrite parent body (approximately 150 kilometers in diameter) collided with another object in the asteroid belt between Mars and Jupiter. The collision caused the breakup of the L-chondrite parent body and created a shower of dust throughout the inner solar system. According to a new study published in the journal Science Advances, measurements of the abundance and composition of cosmic dust in a stratigraphic section in Sweden suggest that shortly after the breakup, the flux to Earth of the most fine-grained extraterrestrial material increased by three to four orders of magnitude. This rain of dust cooled Earth dramatically just prior to the start of Ordovician ice age, which is one of just three major ice ages in the last 500 million years of Earth history. The glaciation event and associated drop in sea level contributed to the faunal turnover in the Great Ordovician Biodiversification Event. READ MORE

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