Late Precambrian, Paleozoic, Mesozoic, and Cenozoic Era Study Guide


Continents shifted, carbon dioxide levels varied, and temperatures altered during the late Precambrian. Many creatures were unable to adapt and died as a result of the changes. Precambrian, Paleozoic, Mesozoic, and Cenozoic are the four primary eras in order of age.

Four primary eras

Four primary erasSource

Late Precambrian era:

Snowball earth during the late Precambrian Source

  • From roughly 2 billion to half a billion years ago, it was the late Precambrian.
  • Earth underwent numerous major geologic and climatic changes throughout this considerable length of time.
  • Continents moved around. They clashed to form a massive supercontinent, then split apart and drifted apart again. Continental drift altered global temperatures and triggered a surge in volcanic activity.
  • The amount of carbon dioxide in the atmosphere fluctuated. This occurred due to a combination of circumstances, including volcanic activity.
  • There was a greenhouse effect when the levels were high.
  • The climate warmed as more heat was trapped on the Earth’s surface. When the levels were low, the globe cooled because less heat was trapped.
  • Earth has experienced extreme cooling on several occasions, leading to the onset of ice ages.
  • One ice age was so cold that it entirely blanketed the earth in snow and ice. Snowball Earth was the name given to Earth during this ice age.

Paleozoic era:

Paleozoic eraSource

  • The Paleozoic Era is the “Age of Life,” spanning from 544 to 245 million years ago. It is divided into six periods: Cambrian Period, Ordovician Period, Silurian Period, Devonian Period, Carboniferous Period, and Permian Period.
  • With a magnificent explosion of fresh life, the age started. The Cambrian explosion is the name given to this event. The period came to an end with the world’s largest mass extinction. The Permian extinction is the name given to this event.
  • The end of the Permian Period prepared the way for a fresh rush of life at the start of the Mesozoic Era. This includes the dinosaurs’ evolution.

Mesozoic era:

Mesozoic eraSource

  • The Mesozoic Era is known as the “Middle Life” era. It’s also known as the Dinosaur Age.
  • It lasted from 245 to 65 million years ago and was separated into three periods: the Triassic, Jurassic, and Cretaceous periods.
  • The Jurassic Period (200–145 million years ago) began following the Triassic Period’s great extinction.
  • Dinosaurs flourished throughout the Jurassic Period as a result of this great extinction.
  • Dinosaurs were at their peak at this period. During the Jurassic, the first birds descended from reptile forebears, as did all of the major mammalian groupings, albeit individual mammals remained tiny.
  • For the first time, flowering plants arose, and new insects evolved to fertilize the flowers.

Cenozoic era:

  • The Cenozoic Era is defined as the era of “modern life”. It is also known as the Mammalian Age.
  • The extinction of the dinosaurs provided an opportunity for mammals. They thrived and soon became the most powerful animals on the planet.
  • The Cenozoic Era began 65 million years ago and is still going on now.
  • The Tertiary period and the quaternary period are the two periods that it may be separated into.


  • The Cambrian explosion marked the start of the Paleozoic Era. The Permian extinction marked the end of the period.
  • Invertebrate creatures in the waters diversified during this time. Plants, amphibians, and reptiles all made the transition to the land.
  • Dinosaurs dominated the Mesozoic Era. They developed from previous reptiles to fill niches on land, sea, and air.
  • Mammals developed as well, although they were much smaller.
  • For perhaps the first time, flowering plants appeared.
  • Dinosaurs died out at the end of the Mesozoic period.
  • Mammalian epochs are known as the Cenozoic Era. They developed to fill almost all of the voids left by dinosaurs.
  • Many extinctions occurred during the Cenozoic Quaternary Period’s ice ages.
  • 12,000 years ago, the last ice age ended. Homo sapiens had evolved by that time.


1. What are the 4 eras in order?

Precambrian, Paleozoic, Mesozoic, and Cenozoic are the four primary eras in order of age. In the geological time scale, periods are a finer subdivision.

2. What are the 4 major divisions of the geologic time scale?

Eons, eras, periods, epochs, and ages are the geologic time divisions, with eons being the longest and ages being the smallest.

3. What is the correct order of eras from oldest to youngest?

Precambrian, Paleozoic, Mesozoic, and Cenozoic are the four primary eras in order of age.

4. What are the 3 eras after the Precambrian era?

Paleozoic (542 million to 251 million years ago), Mesozoic (251 million to 65.5 million years ago), and Cenozoic (65.5 million years ago) are the three primary eons of the Phanerozoic Eon after the Precambrian era.

5. What are different eras?

The geologic time scale (GTS) divides the earth’s history into four periods, each defined by significant events such as the emergence, evolution, and extinction of certain species that help identify one era from the next.

6. What was the late Paleozoic known for?

The Permian Period was the last of the Paleozoic Era, lasting from 299 to 252 million years ago. All continents merged at the start of this epoch to form the supercontinent Pangaea, encompassed by a single ocean named Panthalassa.

7. What is the order of the four eras from longest to shortest duration?

Precambrian Era, Paleozoic Era, Mesozoic Era, and Cenozoic Era are the order of the four eras from longest to shortest duration.

8. How are the eras and periods of the geologic time scale named?

It divides all time into designated abstract time units termed eons, eras, periods, epochs, and ages, in declining order of duration. Stratigraphy, or the correlation and categorization of rock strata, counts these geologic time units.

9. Which is the era of the longest duration?

The Precambrian era was the longest geologic period. It began around 4.53 billion years ago with the world’s creation and concluded roughly 542 million years ago.

10. Which era has the most periods?

The Paleozoic era has the maximum number of periods in it. It is divided into six periods.

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  1. Mesozoic Era. Accessed 11 Dec, 2021.
  2. Paleozoic Era. Accessed 11 Dec, 2021.
  3. Late Precambrian. Accessed 11 Dec, 2021.

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