<Li> Oxygenian Period--2420--2250 MYA--named for displaying the first evidence for a global oxidizing atmosphere </Li> <Li> Jatulian or Eukaryian Period--2250--2060 MYA--names are respectively for the Lomagundi--Jatuli δ C isotopic excursion event spanning its duration, and for the (proposed) first fossil appearance of eukaryotes </Li> <Li> Columbian Period--2060--1780 MYA--named after the supercontinent Columbia </Li> <Li> Mesoproterozoic Era--1780--850 MYA <Ul> <Li> Rodinian Period--1780--850 MYA--named after the supercontinent Rodinia, stable environment </Li> </Ul> </Li>

What is the longest era on the geologic time scale