Geologic Time Scale

Geologic Time Scale

Eons

• Largest unit of time in the geologic time scale
• Divided into four eons: Hadean, Archean, Proterozoic, and Phanerozoic
• Each eon represents a major stage in the Earth's development
• Eons are further divided into eras

Eras

• Smaller unit of time than eons
• Divided into several eras, each representing a distinct phase in the Earth's history
• Eras are characterized by significant geological or biological events
• Examples of eras include the Paleozoic, Mesozoic, and Cenozoic eras

Periods

• Smaller unit of time than eras
• Divided into several periods, each representing a specific interval of time
• Periods are characterized by distinct rock formations and fossil records
• Examples of periods include the Triassic, Jurassic, and Cretaceous periods

Epochs

• Smallest unit of time in the geologic time scale
• Divided into several epochs, each representing a short interval of time
• Epochs are often characterized by specific geological or biological events
• Examples of epochs include the Pleistocene and Holocene epochs

Fossil Record

• The fossil record provides a chronological record of the history of life on Earth
• Fossils are remains or impressions of ancient organisms preserved in rock
• The fossil record is used to date rocks and reconstruct the Earth's history
• Fossils are often used to correlate rock formations and determine the relative age of rocks
• The fossil record provides evidence for evolution and plate tectonics

Geologic Time Scale

Eons

• The largest unit of time, representing a major stage in the Earth's development
• Divided into four eons: Hadean ( Earliest phase of Earth's formation), Archean (oldest life forms), Proterozoic (oxygenation of atmosphere), and Phanerozoic (complex life forms)

Eras

• Characterized by significant geological or biological events, such as the formation of oceans or the development of life
• Examples include the Paleozoic (ancient life forms), Mesozoic (age of reptiles), and Cenozoic (age of mammals) eras

Periods

• Characterized by distinct rock formations and fossil records, such as the Triassic (early dinosaurs), Jurassic (dinosaurs dominate), and Cretaceous (flowering plants and modern mammals) periods

Epochs

• Short intervals of time, often characterized by specific geological or biological events, such as the Pleistocene (ice ages) and Holocene (current epoch) epochs

Fossil Record

• Provides a chronological record of the history of life on Earth through fossil remains or impressions of ancient organisms
• Used to date rocks and reconstruct the Earth's history
• Fossils are used to correlate rock formations and determine the relative age of rocks
• Provides evidence for evolution and plate tectonics