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: -The Hadean Eon, named after the Greek god and ruler of the underworld Hades, is the oldest eon and dates from 4.5–4.0 billion years ago. This time represents Earth’s earliest history, during which the planet was characterized by a partially molten surface, volcanism, and asteroid impacts.

Detailed explanation-3: -The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic Eon, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth’s geologic time.

Detailed explanation-4: -The Azoic era is called the Pre-Cambrian or Alogonican or Archaeanis period of the origin of the continental shelf. At that time the origin of the continental shelf (Pangaea) was formed by the silica-rich granite rocks of less density.