The Rhyacian (IPA: /rʌɪˈeɪsiən/, Greek: Ρυαξ (rhyax), meaning "stream of lava") is the second geologic period in the Paleoproterozoic Era and lasted from 2300 Ma to 2050 Ma (million years ago). Instead of being based on stratigraphy, these dates are defined chronometrically.
The Bushveld Complex and other similar intrusions formed during this period.
2.1 billion year old fossils could be the earliest known multicellular life form. There were found in Gabon, west Africa in 2010. "The 250 or so irregular blobs, up to 12 centimetres in length, have scalloped edges, suggesting an organised and growing colony of coordinated cells." "While other soft-bodied creatures of that age have long since vanished, these organisms were preserved because their body parts were replaced by pyrite, and the sediment around them wasn't buried or cooked.
It is thought likely they emerged at this time to take advantage of a rise in atmospheric oxygen, which began around 200 million years earlier."
2.1 Billion years ago - End of Huronian glaciation. The Huronian glaciation (or Makganyene glaciation) extended from 2400 Mya to 2100 Mya, during the Siderian and Rhyacian periods of the Paleoproterozoic era, triggered by the Great Oxygenation Event (GOE), which oxidised the atmospheric methane (a greenhouse gas). It was one of the most severe and longest ice ages in geologic history, similar to the Snowball Earth ice ages that happened in the Neoproterozoic era.
- Nature, DOI: 10.1038/nature09166