1. Topic: Geologic Time PSSA: 3.5.7.A / S8.D.1.1

2. Objective: TLW identify the major divisions of geologic time (eons, eras, periods, and epochs). TLW identify the major divisions of geologic time (eons, eras, periods, and epochs). TLW identify the characteristics and life forms of the Paleozoic Era and the periods of the Mesozoic and Cenozoic Eras TLW identify the characteristics and life forms of the Paleozoic Era and the periods of the Mesozoic and Cenozoic Eras

3. MI #1: Geologic Time Scale The geologic time scale is the standard method to divide the Earth’s long geologic history into manageable parts. The geologic time scale is the standard method to divide the Earth’s long geologic history into manageable parts. Geologic Time is divided into four major divisions: eons, eras, periods, and epochs) Geologic Time is divided into four major divisions: eons, eras, periods, and epochs) Eon>Era>Period>Epoch Eon>Era>Period>Epoch

4. MI #2: Eons Geologic Time is divided into four eons: Hadean, Archean, Proterozoic, and Phanerozoic. Geologic Time is divided into four eons: Hadean, Archean, Proterozoic, and Phanerozoic. The first three eons are often referred to as Precambrian, while the Phanerozoic eon is subdivided into three eras: Paleozoic, Mesozoic, and Cenozoic. The first three eons are often referred to as Precambrian, while the Phanerozoic eon is subdivided into three eras: Paleozoic, Mesozoic, and Cenozoic.

5. MI #3: Paleozoic Era The Paleozoic era lasted from 543mya to 248mya. (Note – mya stands for million years ago) The Paleozoic era lasted from 543mya to 248mya. (Note – mya stands for million years ago) Marine life was dominant during the first part of the Paleozoic, however, by the end of the era there was abundant life on land. Marine life was dominant during the first part of the Paleozoic, however, by the end of the era there was abundant life on land. The Paleozoic ended with a mass extinction that killed about 90% of all species. The Paleozoic ended with a mass extinction that killed about 90% of all species.

6. MI #4: Mesozoic Era (Part 1) The Mesozoic era is also known as the “age of dinosaurs.” The Mesozoic era is also known as the “age of dinosaurs.” The Triassic Period is the beginning of the era (248mya-206mya); dinosaurs first appear in these rock layers; cone- bearing plants (conifers) were common The Triassic Period is the beginning of the era (248mya-206mya); dinosaurs first appear in these rock layers; cone- bearing plants (conifers) were common

7. MI #5: Mesozoic Era (Part 2) The Jurassic Period (206mya- 144mya) featured the large sauropod dinosaurs and meat eaters like Allosaurus. The Jurassic Period (206mya- 144mya) featured the large sauropod dinosaurs and meat eaters like Allosaurus. The Cretaceous Period (144 mya- 65mya) featured duckbills, ceratopsians, and T-rex; flowering plants appear in the fossil record. The Cretaceous Period (144 mya- 65mya) featured duckbills, ceratopsians, and T-rex; flowering plants appear in the fossil record. The Mesozoic era ended with a mass extinction that was most likely caused by a meteor impact. The Mesozoic era ended with a mass extinction that was most likely caused by a meteor impact.

8. MI #6: Cenozoic Era The Cenozoic era began 65mya and is the current geologic era. The Cenozoic era began 65mya and is the current geologic era. It is often referred to as the “age of mammals.” It is often referred to as the “age of mammals.” It is divided into the Tertiary and Quaternary Periods. It is divided into the Tertiary and Quaternary Periods.

9. So What…? Real Life Application Understanding how scientists interpret geologic time allows us to understand how Earth has changed since its beginning. Understanding how scientists interpret geologic time allows us to understand how Earth has changed since its beginning.