The document discusses the geological time scale, which is a system used by geologists and other earth scientists to describe events in Earth's history. It relates rock layers and the order in which they were formed to specific time periods. The geological time scale is constructed by studying rock strata and using principles like uniformitarianism, as well as fossils, artifacts, and other evidence found in the different layers to determine the relative and absolute ages of formations. It divides Earth's history into eons, eras, periods, epochs, and ages at different timescales from hundreds of millions of years to millions of years.

1. The
Geological
Time
Scale (GTS)
Bedashree Choudhury
14109MWS

3. What is it?
a system of chronological measurement that relates stratigraphy to
time, to describe the timing and relationships between events that
have occurred throughout Earth's history.
Who uses it?
Geologists, paleontologists, archaeologists, anthropologists, and other
Earth scientists.

4. Why do we need to know about it?
History Important events Exploration
Record Calendar Evolution
Dating General knowledge Links; Chains

5. How does one construct a geological time scale?
By studying rock layers [Stratigraphy]
Mining
Bottom-most layer = oldest; topmost layer = newest ← Principle of
Uniformitarianism (geology)
Fossils, artifacts, ecofacts, biofacts; evidence in the different layers

6. Segments of rock
(strata) in
chronostratigraphy
Units
Time spans in
geochronology
Notes to
geochronological
units
Eonothem Eon Half a billion years or
more
Erathem Era Several hundred
million years
System Period Few hundred million
years
Series Epoch Tens of millions of
years
Stage Age Millions of years

7. Age of the Earth : 4.54 ± 0.05 billion years

8. Comparatively...

11. Major extinction events ( The “Big Five”)

12. en.wikipedia.org