Examine the geologic time scale shown here. Which is the longest-lasting period of geologic time? Which is the shortest period? Why should these periods differ so much in duration?

What will be an ideal response?


Answer: The answer should not confuse eons or eras with periods. The period with the longest duration was the Cretaceous at 80 million years. The Silurian was the shortest period of the Phanerozoic, at 28 million years. (These numbers come from subtracting the "start" and "end" dates for each period from the geologic time scale image. The length of the period is based on changes in the fossil record, so the Cretaceous represents an extended time of relative stability in Earth's ecosystems and therefore its fossil record, while the Silurian was relatively a "flash in the pan," a biosphere that was stable for only a (relatively) short time.

Environmental & Atmospheric Sciences

You might also like to view...

What is the name given to a material which slows down enzyme function?

A) closer B) inhibitor C) isozyme D) substrate

Environmental & Atmospheric Sciences

In 1803, Luke Howard, an English naturalist, developed a cloud classification system that employed ____ words to describe clouds as they appear to a ground observer

a. ?German b. ?Greek c. ?Spanish d. ?English e. ?Latin

Environmental & Atmospheric Sciences

As a geologist working in a foreign country for the first time, you are asked to assess the potential for mass wasting in a particular region

What aspects or characteristics (geologic, geographic, biologic, etc.) of the region are you interested in for your assessment? Also, how could you possibly determine if mass wasting has been active in the recent geologic past (100's or 1000's of years)?

Environmental & Atmospheric Sciences

Soils are formed by a series of processes commonly referred to as

A. weathering. B. diagenesis. C. lithification. D. sedimentation.

Environmental & Atmospheric Sciences