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March 29, 2017

Day 2­Precambrian & Paleozoic Era

Precambrian Time & the Paleozoic Era

Day 2­Precambrian & Paleozoic Era

Precambrian time4600 m.y.a ­ 542 m.y.a

• The interval of time in the geologic time scale from Earth's formation to the beginning of the Paleozoic era, from 4.6 billion to 542 million years ago.

• makes up about 88% of Earth's history• know little about its history because the rocks have been so severely deformed and altered by tectonic activity

• Shields: large areas of exposed Precambrian rocks; exist on every continent­­result of several hundred million years of volcanic activity, mountain building, sedimentation, and metamorphism.

precambrian to paleozoic notes.notebook

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March 29, 2017

Day 2­Precambrian & Paleozoic Era

Precambrian time (continued)• Fossils are rare (maybe because life lacked bones, shells, etc.); folding and faulting could have destroyed fossils that formed during this time.> Stromatolites: reef­like deposits formed by blue­green

algae; indicates shallow seas covered much of Earth during this time

> imprints of marine worms, jellyfish, and single­celled organisms have been found from late Precambrian Time.

Day 2­Precambrian & Paleozoic Era

Paleozoic Era542 m.y.a to 251 m.y.a

• the geologic era that followed Precambrian time and that lasted from 542 million to 251 million years ago

• in the beginning, landmasses were scattered• By the end of the Paleozoic, Pangaea had formed• divided into 7 periods

precambrian to paleozoic notes.notebook

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March 29, 2017

Day 2­Precambrian & Paleozoic Era

Cambrian Period542 m.y.a ­ 488 m.y.a

• variety of marine life appeared; more advanced than previous life forms

• new life maybe due to warm, shallow seas that covered much of the continents

• marine invertebrates (no back bone) thrived> trilobites are the index fossil of this time period> brachiopods were the second most common life

form

Day 2­Precambrian & Paleozoic Era

Ordovician Period488 m.y.a ­ 444 m.y.a

• Trilobite population decreases• clam­like brachiopods and cephalopod mollusks became dominant life forms

• large numbers of corals appeared, tiny invertebrates called graptolites flourished the oceans, and primitive fish appeared

• vertebrates appeared (mainly fish)> no jaws or teeth; body covered with thick, bony

plates

Brachiopod ­­ "arm­foot"

Cephalopod ­­ "head­foot"

precambrian to paleozoic notes.notebook

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March 29, 2017

Day 2­Precambrian & Paleozoic Era

Silurian Period444 m.y.a ­ 416 m.y.a

• vertebrate and invertebrate life continued to thrive• echinoderms and corals became more common• eurypterids were scorpion­like creatures that could reach sizes of 3 meters long

• earliest land plants and animals appeared toward end of period

Day 2­Precambrian & Paleozoic Era

Devonian Period416 m.y.a ­ 359 m.y.a

• Age of Fishes• lungfish had ability to breathe air; rhipidistians had strong fins allowing them to crawl onto land

• first amphibians appeared Ichthyostega­­resembled huge salamanders (thought to be ancestors of frogs and toads)

• land plants began to develop (giant horsetails, ferns, seed­bearing plants)

• brachiopods and mollusks thrived

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March 29, 2017

Day 2­Precambrian & Paleozoic Era

Carboniferous Period359 m.y.a ­ 299 m.y.a

• forests and swamps covered much of the land (warm humid climate)

• Coal deposits in Pennsylvania, Ohio, and West Virginia are the fossilized remains of these forests and swamps

• Crinoids flourished in oceans (thought to be ancestors of modern sea lillies

• Giant cockroaches and dragonflies were common on land

Day 2­Precambrian & Paleozoic Era

Permian Period299 m.y.a ­ 251 m.y.a

• marks end of Paleozoic era; mass extinction at end• collision of tectonic plates had joined to form Pangaea, creating the Appalachian Mountains

• shallow inland seas that covered much of the Earth, disappeared, causing trilobites and eurypterids to go extinct

• fossils indicate that reptiles and amphibians survived the environmental changes

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March 29, 2017

Apr 7­8:40 PM