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Earth Evolution
3Earth Evolution
2 Reconstruct
Geological History
Solar System
Archean Proterozoic Early
Late Paleozoic Mesozoic Cenozoic

How to reconstruct Geological History?

Index Fossils

By studying fossils found in successive rock layers - from older to younger - Earth Scientists have discovered the evolutionary sequence of life.

Each time interval has an unique array of fossils, which can be used to date the rocks in which they occur. Some are particularly useful because they occured over a short time span before they quickly became extinct and had a wide geographical range. They are called Index Fossils.

Earth Scientists look for such index fossils in sedimentary rocks to figure out the relative ages of rocks within the worldwide geological time scale. When we find the fossils in rocks from different places in the world, we know that the rocks are of the same age.

Relative Age