Chapter 11: Problem 3

How is the geologic time scale organized? What is the basis for the time scale in relative and absolute terms? What era, period, and epoch are we living in today?

Short Answer

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The Geologic Time Scale is organized by eons, eras, periods, epochs, and ages, based on stratigraphy and radiometric age dating. Currently, we are living in the Phanerozoic eon, Cenozoic era, Quaternary period, and Holocene epoch.

Step by step solution

Understanding the Geologic Time Scale

The Geologic Time Scale is the 'calendar' for events in Earth’s history. It subdivides all time into named units of abstract time called—in descending order of duration—eons, eras, periods, epochs, and ages. These segments of time are based on Earth's stratigraphy, studying rock layers and layering (stratification).

Relative and Absolute Time

The basis for the time scale in relative terms is stratigraphy; older rocks and fossils are found deeper within Earth. Superposition is the principle that in an undisturbed sequence of rocks, the youngest rocks are on top and the oldest are on the bottom. In absolute terms, the time scale is based on radiometric age dating which allows us to precisely determine, in years, how old a rock or fossil is. This method uses decay rates of radioactive isotopes, such as Carbon-14 or Uranium-238, to determine the absolute age of the rocks or fossils.

Identifying Our Current Time

Currently, we are living in the Phanerozoic eon, Cenozoic era, Quaternary period, and Holocene epoch.

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How is the geologic time scale organized? What is the basis for the time scale in relative and absolute terms? What era, period, and epoch are we living in today?

Short Answer

Step by step solution

Understanding the Geologic Time Scale

Relative and Absolute Time

Identifying Our Current Time

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