Precambrian

History of Earth 4600–539 million years ago

The Precambrian ( pree-KAM-bree-ən, -⁠KAYM-; pre-Cambrian, or Cryptozoic, sometimes abbreviated pꞒ or PreꞒ) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic Eon, which is named after Cambria, the Latinized name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time.

From Wikipedia, under CC BY-SA. More on occurri.