Why are time periods in the geologic time scale are not even in length?
Responses
They are based on the thickness of the Earth's rock layers.
They are based on a different type of calendar used to track Earth’s history.
They are based on the type of fossils found in rock layers of the Earth.
They are based on important events happened in Earth’s history.
The correct answer is: They are based on important events that happened in Earth's history.
The time periods in the geologic time scale are not evenly distributed because they are based on significant events that occurred during Earth's history. These events can include major shifts in Earth's climate, mass extinctions, the formation of significant geological features, and the appearance of key organisms.
To determine the length of each time period, scientists examine a variety of evidence, including fossil records, rock layers, and isotopic dating techniques. By analyzing the characteristics of the rocks and fossils from different time periods, scientists can identify and classify unique events and changes that occurred.
For example, the boundary between the Cretaceous and Paleogene periods is marked by a global mass extinction event commonly referred to as the Cretaceous-Paleogene (K-Pg) extinction event. This event, which led to the extinction of the dinosaurs, serves as a significant marker in the geologic time scale and defines the boundary between these two periods.
In short, the lengths of time periods in the geologic time scale are not uniform because they are based on important events and changes in Earth's history, rather than predetermined intervals of time.