Q.49 Arrange the geological history of earth starting from most recent eras
A. Proterozoic
B. Archaeozoic
C. Coenozoic
D. Palaeozoic
E. Mesozoic
Choose the correct answer from the options given below:
- A, B, D, C, E
- A, D, E, B, C
- C, E, D, A, B
- C, D, A, B, E
Cenozoic (C), Mesozoic (E), Paleozoic (D), Proterozoic (A), Archaeozoic (B) represents the correct reverse chronological sequence from most recent to oldest eras. This order follows the geological time scale where Phanerozoic eras precede Precambrian eons.
Question Analysis
The question requires arranging eras from most recent (present → past). Standard geological hierarchy: Phanerozoic Eon (Cenozoic→Mesozoic→Paleozoic) then Precambrian Supereon (Proterozoic→Archean). Archaeozoic = oldest Archean phase.
Option Breakdown
-
A, B, D, C, E: Incorrect. Starts with Proterozoic (2.5-0.54 Ga), not most recent.
-
A, D, E, B, C: Incorrect. Proterozoic first, Cenozoic buried at end.
-
C, E, D, A, B: Correct. Cenozoic (66 Ma-present) → Mesozoic (252-66 Ma) → Paleozoic (539-252 Ma) → Proterozoic (2500-539 Ma) → Archaeozoic (~4000-2500 Ma).
-
C, D, A, B, E: Incorrect. Paleozoic before Mesozoic violates Phanerozoic order.
Correct Answer: C, E, D, A, B.
Geological history of earth starting from most recent eras follows: Cenozoic (Age of Mammals) → Mesozoic (Age of Reptiles) → Paleozoic (Age of Fishes/Invertebrates) → Proterozoic (Early life) → Archaeozoic (First life forms) spanning 4.6 billion years.
Era Timeline & Key Events
Era Code Era Name Time Span Major Events C Cenozoic 66 Ma-present Mammalian radiation, ice ages E Mesozoic 252-66 Ma Dinosaurs, angiosperms, Pangea breakup D Paleozoic 539-252 Ma Cambrian explosion, amphibians A Proterozoic 2500-539 Ma Oxygenation, simple eukaryotes B Archaeozoic 4000-2500 Ma First prokaryotes, stromatolites Memory Framework
“CEM (see ’em) PA (pa) B (baby)”** → Cenozoic, [E]Mesozoic, Paleozoic, Proterozoic, Archaeozoic.
Phanerozoic (visible life) eras first → Precambrian eons. Critical for CSIR-UGC NET Earth Sciences & UPSC Prelims.Exam Trap: Archaeozoic ≠ Archean (Archean includes Archaeozoic + Proterozoic Archean); question uses traditional 5-era classification.
-
