According to scientists, the Earth is approximately this many years old.
He was a Scottish naturalist and farmer who came up with the Principle of Uniformitarianism. He is considered the person who developed the idea of geologic time and proposed that the Earth was much older than people thought at the time.
According to this Principle, geologic processes that occur today are similar to those that have occurred in the past.
This is the actual age of something.
This is the age of rocks and geologic features as compared with other rocks and geologic features nearby.
This man developed a set of principles to compare the ages of rocks.
According to this Principle, in undisturbed rock layers, the oldest rocks are on the bottom.
According to this Principle, sediments are deposited in large, flat sheets.
According to this Principle, if one geologic feature cuts across another feature, the feature that it cuts across is older.
According to this Principle, if one rock contains pieces of another rock, the rock containing the pieces is younger than the pieces of rock it contains.
This is a piece of a rock that has been broken off and become part of a new rock.
These are the preserved remains or evidence of ancient living things.
Rocks and fossils preserve many examples of these when many species on Earth died or became extinct within a relatively short time.
These Principles include Superposition, Original Horizontality, Lateral Continuity, Cross-Cutting Relationships, and Inclusion.