Unit 9 Geological Time

Earth’s History

1. How old is the earth?

1. 4,600,000,000 years (give or take)

Earth’s History

2. What is Geologic Time?

2. A time scale of the history of the earth and life on it

Earth’s History

3. What are the theories about earth forming?

3. A collapsing cloud of dust became the solar systemEarth was one of several clumps of stuff that formed The biggest clump became the sun

Earth’s History

4. Describe earth’s early history.

4.A. The surface was hot with nooceans

B. Gasses from volcanoes formed an atmosphere

C. Some gasses cooled to formliquids and a worldwide ocean

D. 3,800,000,000 years ago, small landmasses formed in the oceans

E. Life started in the oceans

Life on Earth

5. What is a fossil?

5. Fossils are remains or evidence of an organism that lived in the pastUsually an organism that had been buried in sediments

Could be footprints, imprints, petrified, etc.

Used to show how organisms have changed over time

Earth’s History

6. Describe life on earth 2 million years ago.

6. The earth began to settle down from its rumbling, destructive origins. • Changes happened more slowly since then• Processes of Change

a) Weathering – rocks are broken down into smaller particles

b) Erosion – small rock particles are carried away by wind, water, ice, gravity, etc.

c) Deposition – buildup of sediment in low places

d) Uplift – parts of the earth are pushed up to form mountains or plateaus

Geological Time Scale

7. What does it mean, “ record in the rocks?”

7. The rocks contain records of geological time. Geologic time is divided into stages based on important changes of the rocks. The layers of sedimentary rock contain information

Geological Time Scale

8. What isrelative age?

8. Relative age is the age of rocks determined by position of the layers.

Geological Time Scale 9. What is the principle of superposition?

9. The principle of superposition states that the younger layers of rock form layers on top of older rocks. Unconformity, or a line between rock layers that show a break in geological time does occur. Rock layers are horizontal before they deform; faults and igneous intrusions are younger than layers they cut across.

Geological Time Scale

9A: Sketch

Geological Time Scale 10.What is absolute age?

10. Absolute Age is an approximate age in years of a rock as determined by radiometric dating• isotopes decay into more stable atoms• half-life – time it takes for half of a sample to decay

Divisions of Geological Time Scale 11. What is

an era?11. Eras are one of the larger units of geologic time ( eons are the largest) Include 4 major divisions: Precambrian, Paleozoic, Mesozoic, and Cenozoic

Divisions of Geological Time Scale 12. What is

a period of time?

12. A period of time is a subdivision of a geological era; based upon types of life

Divisions of Geological Time Scale 13. What is

an epoch?

13. An epoch is a subdivision of a geological time period.

The Eras: Geological Time Scale14. The Precambrian Era.

14. •4,600 to 640 million years ago• began with the formation of the earth• Cyanbacteria – one of the oldest life forms on Earth which first appeared 3,500 million years ago; began to release oxygen into the atmosphere.• first many-celled organisms over 1,000 million years ago

Paleozoic Era

15. Describe the Paleozoic era.

15. Paleozoic Era – 640 to 245 million years ago• First animals with backbones in oceans• Simple plants on land about 430 million years ago arthropods (bugs) on land about 400 million years ago• Ended with a mass extinction

The Mesozoic Era

16. Describe the Mesozoic Era

16. Mesozoic Era – 245 to 66 million years ago• dinosaurs and flowering plants• most of earth was warm & wet• ended with a mass extinction

The Cenozoic Era

17. Describe the Cenozoic Era? 17. Cenozoic Era –

66 million years ago to now• mammals began to take over• cooler and drier• several ice ages• ends with ?