GEOLOGICAL TIME SCALEGEOLOGICAL TIME SCALE

Section 18.1,18.2 Section 18.1,18.2 By: Christian By: Christian Flores and Flores and

JordanJordan

Section ObjectionsSection Objections

Summarize the development of the geologic Summarize the development of the geologic column.column.

List the major units of geologic time.List the major units of geologic time. identify the characteristics of Precambrian rockidentify the characteristics of Precambrian rock Explain what scientists have learned from the Explain what scientists have learned from the

geological record about life during the Paleozoic geological record about life during the Paleozoic era.era.

Explain what scientist have learned from the Explain what scientist have learned from the geologic record about life during the Cenozoic era.geologic record about life during the Cenozoic era.

New VocabularyNew Vocabulary

• Cenozoic EraCenozoic Era- The most recent geologic era, beginning 65 million years - The most recent geologic era, beginning 65 million years ago; the Age of Mammals. ago; the Age of Mammals.

• EpochEpoch- Subdivision of a geologic period.- Subdivision of a geologic period.• EraEra- Largest unit of geologic time.- Largest unit of geologic time.• Geologic ColumnGeologic Column- Arrangement of rock layers based on the ages of the - Arrangement of rock layers based on the ages of the

rocks.rocks.• InvertebrateInvertebrate- An animal without a backbone- An animal without a backbone• Mesozoic EraMesozoic Era- Geologic era that lasted from 245 million years ago; the - Geologic era that lasted from 245 million years ago; the

Age of Reptiles.Age of Reptiles.• Paleozoic EraPaleozoic Era- Geologic era that followed Precambrian time, lasting from - Geologic era that followed Precambrian time, lasting from

570 million to 245 million years ago.570 million to 245 million years ago.• PeriodPeriod- Subdivision of a geologic era.- Subdivision of a geologic era.• Precambrian TimePrecambrian Time- earliest and longest geologic era lasting from 4.6 - earliest and longest geologic era lasting from 4.6

billion to 570 million years ago.billion to 570 million years ago.• Theory Of EvolutionTheory Of Evolution- Theory that organisms are derived from ancestral - Theory that organisms are derived from ancestral

types.types.• VertebrateVertebrate- An animal with a back bone.- An animal with a back bone.

The Geologic ColumnThe Geologic Column Using the law of superposition and the Using the law of superposition and the

study of index fossils, nineteenth-century study of index fossils, nineteenth-century scientists determined the relative ages of scientists determined the relative ages of rock layers in the areas throughout the rock layers in the areas throughout the world. No single area on the earth world. No single area on the earth contained a record of all geologic time.contained a record of all geologic time.

Scientist combined their observations Scientist combined their observations from around the world to create a from around the world to create a standard arrangement of rock layers standard arrangement of rock layers called now the called now the geologic columngeologic column..

Rock layers in the geologic column are Rock layers in the geologic column are distinguished by the fossils they contain distinguished by the fossils they contain and the rock type.and the rock type.

Divisions of Geologic Divisions of Geologic TimeTime Is divided into units.Is divided into units. Geologist use events like earth’s Geologist use events like earth’s

geologic history, major changes in geologic history, major changes in the earth’s surface or climate the earth’s surface or climate changes to dived them into units.changes to dived them into units.

A unit is often characterized by A unit is often characterized by fossils of a dominant life-form.fossils of a dominant life-form.

ErasEras

A very large unit of geologic time is an era.A very large unit of geologic time is an era.Earliest is Precambrian Era. It is known more as Precambrian time Earliest is Precambrian Era. It is known more as Precambrian time because it is much longer then other geologic eras. When this era because it is much longer then other geologic eras. When this era started earth’s crust was just beginning to solidify. It lasted for 4.6 started earth’s crust was just beginning to solidify. It lasted for 4.6 billion yearsbillion yearsPaleozoic Era followed Precambrian time. It means “ancient life”. It Paleozoic Era followed Precambrian time. It means “ancient life”. It lasted 325 million years. They contain fossils of marine and land lasted 325 million years. They contain fossils of marine and land plants and animals.plants and animals.Mesozoic Era followed the Paleozoic Era. It “means middle life”. Mesozoic Era followed the Paleozoic Era. It “means middle life”. These fossil's contain more complex forms. It lasted 180 million These fossil's contain more complex forms. It lasted 180 million years.years.The Cenozoic Era followed the Mesozoic Era. It means recent life. The Cenozoic Era followed the Mesozoic Era. It means recent life. The fossils of mammals are common in this era. This era started 65 The fossils of mammals are common in this era. This era started 65 million years ago and still continues today.million years ago and still continues today.

Periods and EpochsPeriods and Epochs

Eras have been divided into shorter times Eras have been divided into shorter times called periods. Each period is called periods. Each period is characterized by specific fossils and characterized by specific fossils and usually named for the location in which the usually named for the location in which the rocks containing the identifying fossils.rocks containing the identifying fossils.

Epochs are even shorter time periods then Epochs are even shorter time periods then periods.periods.

Precambrian TimePrecambrian Time Began nearly 4.6 billion years ago and Began nearly 4.6 billion years ago and

ended 570 million years ago.ended 570 million years ago. It makes nearly 88% of earth’s history.It makes nearly 88% of earth’s history. Large areas of exposed rock Precambrian Large areas of exposed rock Precambrian

rocks, called shields are found in every rocks, called shields are found in every continent, one of these shields covers continent, one of these shields covers much of eastern Canada.much of eastern Canada.

Fossils are rare in Precambrian rocks Fossils are rare in Precambrian rocks because the life forms used to have soft because the life forms used to have soft bodied. These organisms lacked bones, bodied. These organisms lacked bones, shells and other hard parts needed to shells and other hard parts needed to make a fossils.make a fossils.

The Paleozoic era The Paleozoic era

Began 570 million years ago ended 245 Began 570 million years ago ended 245 millions years agomillions years ago

Had Cambrian period, Ordovician period, Had Cambrian period, Ordovician period, Silurian Period, Devonian Period, Silurian Period, Devonian Period, Carboniferous Period, Permian Period.Carboniferous Period, Permian Period.

The Mesozoic EraThe Mesozoic Era

Began 245 million years ago ended 65 Began 245 million years ago ended 65 million years ago.million years ago.

Had Triassic Period, Jurassic Period, and Had Triassic Period, Jurassic Period, and Cretaceous Period.Cretaceous Period.

The Cenozoic Era The Cenozoic Era

Began 65 million years ago and it still Began 65 million years ago and it still continues today.continues today.

Had Quaternary Period, and Tertiary Had Quaternary Period, and Tertiary Period.Period.

Also had these epochs Holocene, Also had these epochs Holocene, Pleistocene, Pliocene, Miocene, Pleistocene, Pliocene, Miocene, Oligocene, Eocene, Paleocene.Oligocene, Eocene, Paleocene.