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Q79
(NDA-II/2023)
Geography › World Physical Geography
Official Key
Which one of the following is the oldest era in Geological History determining the age of various rock types ?
Explanation
The Precambrian is the oldest and longest span of Earth's history, accounting for approximately 88% of the total geological time scale. It extends from the formation of Earth, about 4.6 billion years ago, to the beginning of the Cambrian Period, approximately 541 million years ago.
The Precambrian is technically a "Supereon" comprising the Hadean, Archean, and Proterozoic eons. Most of the Earth's oldest igneous and metamorphic rocks, which form the stable cores of continents (cratons), date back to this era. The other options provided belong to the Phanerozoic Eon, which followed the Precambrian:
- Paleozoic Era: 541 to 252 million years ago.
- Mesozoic Era: 252 to 66 million years ago (Age of Reptiles).
- Cenozoic Era: 66 million years ago to the present (Age of Mammals).
Thus, the Precambrian is the oldest among the given choices.
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