Geologic History of the Earth

Ch 13 April 14, 2010

Warm up 4/14

• What span of time does the geologic time scale cover?

• Rank eons, eras, epochs, and periods in order from LARGEST to smallest

• What is the “era of ancient life” called?• A footprint of a dinosaur would be what type

of fossil?

The Early Earth- Precambrian

• The Precambrian Era covers an immense amount of geologic time– Started at the beginnings of Earth 4.6 billion years

ago and lasted over 4 billion years– The fossil record extends back only 3.5 billion years

• Stromatolites are distinctively layered mounds or columns of calcium carbonate. They are not the remains of actual organisms but are the material deposited by algae.

Precambrian

Everything else

The Early Earth- Precambrian

• Originally, the Earth’s atmosphere had no free oxygen

• The atmosphere was made of gases similar to those released in volcanic eruptions- water vapor, carbon dioxide, nitrogen, and other gases to a small extent

• WHY WOULD THIS BE A PROBLEM?

Because with no free oxygen humans can’t live

The Early Earth- Precambrian

• What releases O2?• GREEN PLANTS• The major source of the free oxygen in our

atmosphere is green plants through photosynthesis

The recent 540 million years

• After the Precambrian the Phanerozoic era is divided into three eras that cover about 540 million years– Paleozoic– Mesozoic– Cenozoic

Paleozoic• Early Paleozoic

– During the Cambrian, Ordovician, and Silurian periods the continents of South America, Africa, Australia, Antarctica, and part of Asia formed the super-continent of Gondwana

Paleozoic

• Life in the early Paleozoic was restricted to the seas

Paleozoic

• Late Paleozoic• By the end of the

Paleozoic, all of the continents were fused together to form Panagaea

Paleozoic

• Late Paleozoic Life–About 400 million years ago plants had

adapted to survive on the water’s edge–Plants then began to move inland

• This made it possible for animals to move onto land

• WHY?

Paleozoic

• Amphibians (animals that spend part of their time in the water and part on land) diversified

• Reptiles became the first true terrestrial animals

• Large tropical swamps in the Pennsylvanian period in North America eventually formed the vast coal deposits that support the US economy

Paleozoic

Watch video here.

Paleozoic

• The great extinction at the end of the Paleozoic was the caused by dramatic climate changes

• The Paleozoic extinction was the largest of at least five mass extinctions to occur over the past 500 million years

Mesozoic- Age of Reptiles

• Pangaea began to break up• Dinosaurs were the land-dwelling reptiles that

thrived during the Mesozoic• See a video of dinosaurs here!• Gymnosperms are plants with seeds that do

not depend on free-standing water– These became the dominant plants of the

Mesozoic

Mesozoic- Age of Reptiles

• Reptiles have eggs with hard shells• This allows the eggs to be laid on land so that

organisms no longer needed water to reproduce and develop

• Reptiles dominated the Mesozoic• At the end of the Mesozoic many reptile

groups and plants died– A meteorite collision caused large amounts of dust

to fill the atmosphere and block sunlight

Cenozoic- Age of Mammals

• The Earth is currently in the Cenozoic era• The Cenozoic is also known as the Age of

Mammals• See video here!• The Cenozoic is divided into two periods

– Tertiary (almost all of the Cenozoic)– Quaternary (relatively short period in which we

live)

Cenozoic- Age of Mammals

• During the Cenozoic, Western North America was subject to a lot of plate interactions that caused earthquakes, mountain building, and volcanism

Cenozoic- Age of Mammals

• Dominant Life Forms• Mammals- animals that bear live young and

have a steady body temperature• Angiosperms- flowering plants with covered

seeds- seeds could now travel and plants could spread

• DINOSAURS WERE NO LONGER LIVING

Filling out your Geologic Time Scales• Using your notes and your text book (Ch. 13, page 353

and 365) fill in any missing eon, era, period, and epoch information

• Fill in the Development of Plants and Animals column of the time scale– You need to have a major event for each block of the paper.– HINT: start with the Cenozoic and move backward in time,

it’ll be slightly easier• Color each Era and period to distinguish them from the

others.• When you finish, begin working on your study guide

ALONE, quietly.

Exit Ticket

• True or False: Mammals became dominant after dinosaurs were extinct

• The current geologic age is the Age of ______• What caused the mass extinction at the end of

the Paleozoic?• What caused the mass extinction at the end of

the Mesozoic?• What was formed in the swamps of the North

America during the Pennsylvanian period?

Warm-up: 4/15/10

• OPEN NOTES QUIZ• Collect together all of your notes for CH. 12

and CH. 13• Make sure you have a book on your desk

AGENDA 4/15/10

1. Quiz2. Project Description3. Work on study guides to prepare

for tomorrow4. Earth Revealed video on

Geologic Time

AGENDA 4/15/10

1. Quiz2. Project Description3. Work on study guides to prepare

for tomorrow4. Earth Revealed video on

Geologic Time

AGENDA 4/15/10

1. Quiz2. Project Description3. Work on study guides to prepare

for tomorrow4. Earth Revealed video on

Geologic Time

AGENDA 4/15/10

1. Quiz2. Project Description3. Work on study guides to prepare for

tomorrow4. Earth Revealed video on Geologic Time

Do not forget, you have a test tomorrow and your study guides will be turned in!!!

Warm up 4/16

1. A gap in the rock record is what?2. The time it takes for 50% of the nuclei in a

radioactive sample to decay to its stable isotope is called what?

3. What length of time does the geologic time scale cover?

4. How far back does the fossil record extend?5. Mammals became dominant only after what

became extinct?

Essay Question• In a full paragraph (5-8 sentences) Explain the

difference between relative dating and radiometric dating. – Make sure to:

• Define relative dating• Define radiometric dating• Explain the difference• Relate them to the geologic time scale.

• When you finish get the article report and continue to work quietly.