GENERAL GEOLOGY

Detailed explanation-1: -The Precambrian encompasses the Archean and Proterozoic eons, which are formal geologic intervals that lasted from 4 billion to about 541 million years ago, and the Hadean Eon, which is an informal interval spanning from 4.6 billion to 4 billion years ago.

Detailed explanation-2: -In the last few decades, however, geologists have found that there are some hard-to-discern fossils in some Precambrian rocks, so this period is now also known as the Cryptozoic or “obscure life” Eon (from the words “crypt” = “hidden, ” and “zoon” = “life").

Detailed explanation-3: -The term “Precambrian” is recognized by the International Commission on Stratigraphy as the only “supereon” in geologic time; it is so-called because it includes the Hadean ( 4.6–4 billion), Archean (4–2.5 billion), and Proterozoic (2.5 billion-541 million) eons.

Detailed explanation-4: -The Precambrian is the largest span of time in Earth’s history before the current Phanerozoic Eon (the largest division of geologic time, comprising two or more eras) and is a supereon divided into several eons of the geologic time scale.