Calymmian

The Calymmian (from Ancient Greek: κάλυμμα, romanized: kálymma, meaning 'cover') is the first geologic period in the Mesoproterozoic Era. It lasted from 1600 to 1400 million years ago (Ma) and spanned 200 million years. This period followed the Statherian Period from the Paleoproterozoic Era and came before the Ectasian Period. These dates are set using special scientific methods instead of studying rock layers.

During the Calymmian, existing areas of land grew larger, and new ones formed on bases that had recently become stable.

Around 1500 million years ago, the huge landmass called the supercontinent of Columbia began to break apart. Also, special ancient life forms known as the Volyn biota lived around this time.