Where did scientist get information to develop the geologic time scale?

a) They collected and studied rock samples in Africa.

b) They studied rock layers and index fossils around the world.

c) They conducted research at libaries.

d) They didn't have any information; they just made an educated guess.

http://pubs.usgs.gov/gip/fossils/numeric.html

The correct answer is b) They studied rock layers and index fossils around the world.

To develop the geologic time scale, scientists used a combination of methods and information from various sources. One key source of information came from studying rock layers, which are formed over millions of years and contain important clues about Earth's history. By examining the sequence and characteristics of different rock layers in different locations worldwide, scientists were able to identify patterns and establish a timeline of Earth's past.

Another important factor in developing the geologic time scale was the use of index fossils. Index fossils are specific types of fossils that are found in a particular time period and can be used to correlate and match rock layers from different regions. Scientists relied on the presence of index fossils to determine the relative ages of rock layers and establish a standardized chronological framework.

These methods were not based on an "educated guess," but rather on careful observation, evidence, and analysis. It's important to note that scientific understanding is always subject to revision and refinement as new evidence emerges.