precambrian to paleozoic notes.notebook
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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
precambrian to paleozoic notes.notebook
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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
precambrian to paleozoic notes.notebook
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March 29, 2017
Apr 78:40 PM
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