Geological Time Periods of the Earth

By: Matthew Bassett

Cenozoic eraContinents and Oceans

•The size and formation of continents finally took on their modern shapes, as seas developed and continents became joined by other land

masses.◦They reached their modern locations by the Pleistocene.

•North America became a dryer continent than during the Cretaceous as sea levels dropped due to glacier formation.

•Modern mountain ranges appear.

Climate

•The climate changed from a tropical greenhouse to a world where 1/3 of the land masses were covered in deep glaciers.

◦For the last 150 years, the climate has begun to gradually warm again.

The Paleogene Period

• 65 to 23 Million Years Ago

• •By 55 million years ago, the climate became a greenhouse environment with tropical temperatures covering most of the globe.

• •As the continents moved about, the ocean currents changed, lowering the worldwide temperatures and increasing the seasonal nature of the climate.

• Plant Life

• •Most of the Cretaceous plant life died out with the calamitous events surrounding the asteroid impact, but it wasn’t too long until the flowering plants were flourishing once again.

• •Conifers, too, made a comeback and appeared on all continents.• •With the cooling temperatures in the middle of the Paleogene, the lush vegetation of the greenhouse

climate was replaced by open savannahs as the forests disappeared in the increasingly seasonal climate.• •With the savannahs came all types of grasses which appear now for the first time.

• Animal Life • •Mammals• ◦Immediately after the Cretaceous the size of mammals, especially herbivores, increased dramatically as

they filled in the vacant niches left by the dinosaurs.• ◦Other mammals included the camel, rhinos, proto-horses, primates such as lemurs and bats.• ◦The first animals with a rumen (another type of stomach) appeared in the late Oligocene. This allowed

the animals to digest the tough vegetation and enabled a diverse group of animals to develop.• .

65 to 23 Million Years Ago

The Paleogene Period•Birds

◦Large flightless birds appeared, dominating the niche of top predator in South America for most of the Cenozoic Era.

◦By the middle of the Paleogene, modern birds appeared in the forms of eagles, vultures and even pelicans.

•Insects◦Insects seemed to have suffered a serious setback after the Cretaceous Extinction and it wasn’t until nearly 10 million years had passed that the insects began to recover in

numbers and variety.•Marine LIfe

◦Marine life looked more like our modern forms than had the Cretaceous and sharks became plentiful with many different body types.

◦There were many types of bony fishes as they continued to diversify.◦Early whales appeared in the Eocene, and by the Oligocene they had diversified into

toothed whales and baleen whales. Extinction Events

•Around 55 million years ago an extinction event decimated the plankton in certain areas of the oceans. It is thought by some that the warming temperatures caused the

release of frozen methane hydrates at the bottom of the oceans, killing the more vulnerable species.

•A second extinction occurred around 35 million years ago

Neogene period

• 23 Million Years Ago to Present day• One of the significant attributes of the Neogene

was the occurrence of geological events that shape our modern world. Many of the world’s great mountain ranges arose as the continents and tectonic plates continued in their relentless movement. Where once the continents were separate islands, many continents began to be joined by land bridges (North and South America) or by smaller land Damasses

Mesozoic Era250 to 65 Million Years Ago

Mesozoic means "middle animals," and is the time during which the world fauna changed drastically from that which had been seen in the Paleozoic. Dinosaurs which are perhaps the most popular organisms of the Mesozoic, evolved in the Triassic, but were not very diverse until the Jurassic. Except for birds, dinosaurs became extinct at the end of the Cretaceous. Some of

the last dinosaurs to have lived are found in the late Cretaceous deposits of Montana in the United States.

Triassic The Triassic is a time of tremendous and phenomenal change, and a major

reason for this innovation is the Triassic falls upon the heels of the great Permian Extinction when as much as 95% of life on Earth was destroyed in a mass extinction event of vast proportions. What makes the Triassic so very

interesting is it provides insight into how Life was able to rebound and adapt to the new and difficult environment that dominated most of the Triassic Period.

Main Events for the Triassic Period•There was slow recovery after the Permian Extinction

•Oxygen levels in the atmosphere reached its lowest in 500+ million years•The supercontinent Pangea began to break apart

•The Triassic extinction at the end of the Period eliminated more species than any other extinction

•The following made their first appearance:◦Dinosaurs◦Pterosaurs◦Mammals

◦Bees, ants, mosquitoes and flies

Jurassic period

• 200 to 145 Million Years Ago Climate

• •The climate began to warm as Pangea broke apart. The ocean currents could now flow around each individual continent, moderating the climate and providing shallow marine habitats with the increase in available coastlines.

• •By the Late Jurassic, the climate was warm and tropical with lush vegetation – very park-like!• •No glaciers were present at the poles.

• Plant Life

• •Seed ferns, horsetails, ginkgos, conifers and cycads continued to be common.• •The plant species multiplied in response to the higher CO2 levels, and at first, enjoyed the

warmer weather; but as temperatures began to climb higher and higher, the plants became more and more stressed.

• Animal Life

Jurassic period part 2

• •Birds • ◦The first birds appeared (such as Archaeopteryx). • ■We now have many fossils bearing the unmistakable imprint of feathers as scientists try to piece together

the lineage and origin of birds• •Pterosaurs • ◦Pterosaurs continue to diversify and multiply, branching out into the Pterodactyl line, creating some

magnificent varieties of these flying reptiles.

• ■Pterosaurs appear on every continent in all shapes and sizes.

• •Dinosaurs• ◦Sauropods like Apatosaurus (aka Brontosaurs) continue to diversify into many different types. While not

abundant in the Early Jurassic, by the Late Jurassic they were dominant, coming in many forms and sizes. These giant creatures were some of the largest animals to have every lived.

• ■Dinosaur physiology remains controversial. Were they warm-blooded or cold-blooded? How did they grow so enormous? How did they breathe?

• ■Respiration, oxygen levels and air sacs played a significant role, both in the context of oxygen efficiency as well as the accommodation of the enormous dimensions attained by many dinosaurs during this period.

• ■Other familiar dinosaurs included Stegosaurs, Iguanodons, Ankylosaurs and Allosaurs (forerunners of the Tyrannosaurus Rex).

Jurassic period• •Mammals• ◦Mammals continued to be small, although they were able to diversify and fill many biological niches filled by insects

today. These small creatures scurrying through the underbrush were still millions of years away from their future dominance.

• •Marine LIfe• ◦Inhabiting the oceans were various forms of marine reptiles: Plesiosaurs and Ichthyosaurs, all types of sharks and bony

fishes, as well as numerous types of ammonites and shell fish.• ◦The warm, shallow seas of the Late Jurassic promoted thriving communities of bivalves and other shallow water

creatures.

• ■Coral reefs flourished in a multitude of shapes and sizes, providing habitat for many species.• ■Sponges flourish and diversify adding their variety to the great coral reefs.• •Fresh Water • ◦The first modern-type crocodiles appear in the fresh waters joining the many turtles and amphibians and croc-like

relatives already enjoying the warm waters.• •Insects• ◦Wasps first appear.• ◦Beetles develop into a myriad of forms and even today they are the most common form of insect.

• Extinction Events

• •A minor extinction occurred at the end of the Early Jurassic, approximately 190 million years ago.

• •Another, more devastating extinction occurred at the end of the period. Many of the well-known dinosaurs disappeared from the landscape: the giant sauropods (Apatosaurus, Diplodocus, etc.) as well as Stegosaurs. The marine communities also suffered considerably. The cause of this extinction is unknown .

The Cretaceous Period• 145 to 65 Million Years Ago• Most of the Cretaceous was warm and tropical, giving rise to a variety of plants and animals many of which still exist in

one form or another in our modern world – dinosaurs not included, thankfully.Flowering plants flourished early in the Cretaceous, revolutionizing the diet of most animals and spurring on the development of diverse forms of insectsPlant Life

•Angiosperms (flowering plants) become the dominant plant of the Cretaceous, revolutionizing insect and dinosaur development alike.

◦There is debate among the scientists as to what made the angiosperms so successful.

Animal Life

•Dinosaurs◦Dinosaurs of every shape and size are in abundance

■Tyrannosaurs were a major predator in the Cretaceous. The most well-known member of this group being the Tyrannosaurus Rex.

■Joining Tyrannosaurus in the super predator category were the Spinosaurs and Carcharodontosaurs (“shark-toothed lizard”). (The Spinosaur was actually larger and heavier than a T Rex.)■Some of the familiar dinosaurs that emerge in the Cretaceous are Iguanodons, the duck-billed Hadrosaurs and Triceratops.

■For the Pterosaurs it was their high point, their giant size dwarfing the smaller proto-birds who were developing rapidly and would dominate the skies of the post-Cretaceous world

Paleozoic EraThe Paleozoic Era is the beginning of an explosion of life forms. The Cambrian Explosion marks the era with thousands of new

life forms in the ancient seas.

There was certainly life before the Cambrian Period. There were even many complex life forms. In late Precambrian time was a period called the Ediacaran. Ediacaran fossils are found in the

Ediacaran Hills of Australia, Northwest Territories, Yukon, British Columbia, and Newfoundland in Canada. There are many

different types of Ediacaran fossils. What distinguishes these fossils is that there are no hard body parts to fossilize. This makes

them very rare. Generally soft tissue disintegrates long before fossilization can take place except in these few locations. The

other distinguishing characteristic is that Ediacaran life forms are nothing at all like those of the Cambrian Period!

The Cambrian Period

540 to 490 Million Years Ago

The Cambrian was inhabited by wondrous life forms, many of which would seem alien

to our modern senses and it is the “Cambrian Explosion” that sets this period apart. Early in this period a large number of experimental,

unprecedented life forms appeared, differing greatly from one another. Remarkably these creatures did not differ on the species level,

as does a tiger from a whale, but their differences were more profound

The Ordovican Period 490 to 440 Million Years Ago

• •After the Cambrian Extinction, life rebounded during the Ordovician as the oxygen levels began to rise and the seas receded from the continents for a time. Life began to thrive on the land and in the sea. While the number of phyla in the Ordovician was few compared to the Cambrian, there were families in abundance: 150 families existed during the Cambrian compared to the 400 in the Ordovician. This means that while there was not the huge variety of body plans as those found in the Cambrian, there were greater numbers and varieties within each body structure: more types of trilobites, more types of brachiopods, etc.

The Silurian Period

440 to 415 Million Years AgoThe melting of the Ordovician glacial ice produced a warm, stable climate during the Silurian, providing the perfect conditions for Life to flourish. Silurian plants developed a vascular structure giving their stalks the strength to grow as high as three feet without the support of a watery environment. This new vascular structure also allowed them to transport nutrients to both stem and stalk. And while they were as yet leafless, these early plants were able to photosynthesize their nutrients through their stems.

The Devonian Period

• 415 to 360 Million Years Ago• The Devonian period was a time of many “firsts”:

the first amphibians, the first sharks, the first plants with roots, leaves and stomata. Despite such significant innovations, the Devonian is best known for its diversity and abundance of fish. Not only did fish with cartilage first appear (such as sharks), but fish with bony skeletons developed and it is this type of fish which today comprises a majority of our modern fishes.

The carboniferous period

• 360 to 300 Million Years Ago• During this period, the advancement of Life is moving

at an astonishing pace. Amphibians lose their fish-like appearance and become more familiar to our modern eyes. Reptiles arrived on the scene, preferring dry land to the wet environments of their amphibious relatives. By the end of the Carboniferous, three great lines of reptiles have emerged: the diapsids, ancestors to dinosaurs, lizards and birds; the synapsids, ancestors to mammals; and the anapsids, ancient ancestors of turtles.

The Permian Period • The geography of the Permian was spectacularly different from today. All the

continents had joined together to form the great supercontinent of Pangea. With one ocean and one land mass, the climate of Earth began to warm and become more arid.

• A significant factor in the Permian was the dramatic drop in oxygen levels. After reaching its high during the Carboniferous, oxygen began to disappear from both the atmosphere and the oceans, severely impacting all walks of life with one exception: plants, which thrive on carbon dioxide.

• Paradoxically it was the rising carbon dioxide levels that most significantly affected the plants. As CO2 levels rose, plant life flourished for a while; but then the world became warmer and drier to the point that plants could no longer cope with the excessive heat and aridity

Web links http://www.google.com/imgres?imgurl=http://cdn.dipity.com/uploads/events/

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http://www.google.com/imgres?imgurl=http://eonsepochsetc.com/Cenozoic/Neogene/Neog_Images/Wolly_Mammoth.jpg&imgrefurl=http://eonsepochsetc.com/Cenozoic/Neogene/

Neogene_home.html&usg=__15dTk9c_AJ_xWLrj1k5sQA0Wsg8=&h=321&w=500&sz=39&hl=en&start=4&zoom=1&tbnid=X4dfr5J-PAWvUM:&tbnh=83&tbnw=130&ei=KRetT8zLLOeS0QH28diDDA&prev=/search%3Fq

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http://eonsepochsetc.com/Mesozoic/mesozoic_home.htmlhttp://www.ucmp.berkeley.edu/mesozoic/mesozoic.php

http://disney-clipart.com/Meet-Robinsons/T-Rex.php

http://www.fossils-facts-and-finds.com/paleozoic_era.html

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