Which of the following represents the longest time period?

Which of the following represents the longest time period?

In formal usage, eons are the longest portions of geologic time (eras are the second-longest). Three eons are recognized: the Phanerozoic Eon (dating from the present back to the beginning of the Cambrian Period), the Proterozoic Eon, and the Archean Eon. Less formally, eon often refers to a span of one billion years.

What is the difference between the Precambrian eon and Phanerozoic eon?

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.

What fossils were found in the Cenozoic Era?

Common Cenozoic fossils include cat-like carnivores and early horses, as well as ice age fossils like wooly mammoths. Caves can preserve the remains of ice-age animals that died in them or were transported there after death.

Which unit of geologic time is the oldest?

Paleozoic Era
The Paleozoic Era is the oldest of the three Eras and dates from 540 Million to 248 Million Years Ago.

Which of the following represents the longest time period on Earth’s geological timescale?

Explanation: The Precambrian lasted from about 4.6 billion to 541 million years ago.

Which of the following era is considered as the time of ancient life?

Most of our knowledge of the fossil record comes from the three eras of the Phanerozoic eon. The Paleozoic (“old life”) era is characterized by trilobites, the first four-limbed vertebrates, and the origin of land plants.

What is the difference between Precambrian time and Paleozoic Era?

The most significance difference between Precambrian and Paleozoic life forms is that Precambrian life forms had soft body parts and Paleozoic lifeforms had hard body parts. What is the difference between animal life in the Mesozoic Era and the early Cenozoic Era?

Which is a difference between the Paleozoic and Mesozoic era Brainly?

The first birds emerged in the Paleozoic era while mammals first emerged in the Mesozoic. Many different species of dinosaurs lived in the Mesozoic, but they all died off in the Paleozoic. Animal complexity increased during the Paleozoic while the first flowering plants appeared in the Mesozoic era.

What does fossil evidence reveal about the Cenozoic Era?

Those that could adapt to the changes in the environment survived; those that could not were doomed to extinction. A rich fossil record in rocks relatively undisturbed by geological forces reveals the history of both. The Cenozoic is when the continents moved to their current positions.

What is the Cenozoic era best known for?


  • The Cenozoic Era is the age of mammals. They evolved to fill virtually all the niches vacated by dinosaurs.
  • The ice ages of the Quaternary Period of the Cenozoic led to many extinctions.
  • The last ice age ended 12,000 years ago. By that time, Homo sapiens had evolved.

Which unit of time is the earliest and longest unit?

Units of Time

  • Eons, or Eonothems, are the largest division of time, lasting thousands of millions of years.
  • Eras, or Erathems, are the subdivisions of eons.
  • Periods, also referred as “systems”, are the subdivisions of eras and typically last tens of millions of years.

Which unit of geologic time is the oldest quizlet?

The Precambrian is the oldest and longest of the this, comprising 90% of geologic time.

What are the four eons of geological time?

Left: the four eons of geological time. Right: the “Precambrian” eons (Hadean, Archean, and Proterozoic) represent 88% of geological time. Image by Jonathan R. Hendricks.

Which is the youngest eon of geological time?

We live during the Phanerozoic, which means “visible life.” This is the interval of geological time characterized by abundant, complex fossilized remains. Being the youngest eon of time, it is also very well represented by rock at Earth’s surface (because of the Principle of Superposition; see Section 1 ).

Which is the broadest category of geological time?

The eon is the broadest category of geological time. Earth’s history is characterized by four eons; in order from oldest to youngest, these are the Hadeon, Archean, Proterozoic, and Phanerozoic. Collectively, the Hadean, Archean, and Proterozoic are sometimes informally referred to as the “Precambrian.”…

When did the Phanerozoic eon begin and end?

You have already learned that the Earth is 4.54 billion years old. The Phanerozoic eon began 541 million years ago (or, 0.541 billion years ago). Thus, the Phanerozoic eon represents a paltry 12% of Earth’s history! Instead, most of Earth’s history is represented by the three Precambrian eons.

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