Geologic Time Overview

Multiple Select

How many years old is the Earth?

• 4.6 byo

• 4,567 myo

• 600 years old

• Unknown

Multiple Choice

What Epoch are we currently living in?

• Eocene
• Holocene
• Miocene
• Pleistocene

Open Ended

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Multiple Choice

Which of the following best describes a mass extinction?

• A time period when a large percentage of all known living species go extinct

• A time period when only one species goes extinct

• A time period when new species evolve rapidly

• A time period when climate remains unchanged

Multiple Select

Which of the following are types of fossils?

• Petrified

• Mold

• Carbon film

• Coprolite

Open Ended

What characteristics make index fossils useful for dating rock layers?

Multiple Choice

Which law states that in any undisturbed sequence of rock layers, the oldest layer is at the bottom and the youngest layer is at the top?

• Law of Superposition

• Law of Cross-Cutting

• Law of Relative Dating

• Law of Radioactive Decay

Open Ended

Explain how the Law of Superposition and the Law of Cross-Cutting help scientists determine the relative ages of rock layers.

Multiple Choice

Which of the following statements about radioactive decay and half-life is correct?

• Half-life is the time needed for all atoms in a sample to decay.

• Radioactive decay helps scientists determine the numeric age of rocks.

• Radioactive decay only occurs in sedimentary rocks.

• Half-life is not related to radioactive decay.

Multiple Choice

What is the primary basis for dividing the history of Earth into time units according to geologists?

• The color of rocks

• The location of rocks

• The fossils contained within the rocks

• The size of rocks

Open Ended

Describe how the geologic time scale organizes Earth's history and what information it provides about the relationships between eons, eras, periods, and epochs.

Multiple Choice

Which eon is the largest unit of geologic time and encompasses the others?

• Phanerozoic

• Proterozoic

• Archean

• Eon

Open Ended

Explain the significance of the Precambrian in Earth's history and describe the types of life forms that existed during this time.

Multiple Choice

Which of the following statements about cyanobacteria during the Proterozoic eon is correct?

• They were the first animals to evolve.

• They added oxygen to the atmosphere via photosynthesis.

• They caused mass extinction events.

• They were responsible for the formation of continents.

Open Ended

Describe how periods within the geologic time scale are named and what distinguishes them from eras.

Multiple Choice

Which event marks the end of the Paleozoic Era?

• The appearance of land plants

• The diversification of multicellular life

• The largest mass extinction event in Earth's history

• The formation of large coal deposits

Open Ended

Describe the types of life forms that dominated the oceans during the Paleozoic Era, as shown in the illustration.

Multiple Select

Which of the following periods are part of the Mesozoic Era?

• Triassic

• Jurassic

• Cretaceous

• Carboniferous

Open Ended

How did the diversity of mammals and birds change during the Cenozoic Era?

Multiple Choice

Which of the following animals would most likely be found in the Cenozoic Era, based on the illustration?

• Trilobite

• Woolly mammoth

• Tyrannosaurus rex

• Ammonite

Multiple Choice

Which era on the geologic time scale is characterized by the appearance of modern seed-bearing plants and dinosaurs?

• Cenozoic

• Mesozoic

• Paleozoic

• Precambrian

Open Ended

How do fossils help scientists understand the history of life on Earth?