Geologic Time Line

1. Geologic Time Line October 19, 2010

3. Hadean Era • Scientists have generally thought that during the Hadean period the solar system was forming out of a spinning cloud of dust and gases called an accretion disk. At the center of the cloud, heavier particles drew together through gravitational force until nuclear fusion set it ablaze in light and heat….The birth of our sun.

4. Hadean continued • Scientists also believe that the Earth and other planets would have been molten at this stage of development. As the Earth cooled, the heavier molten iron sank into the core, while lighter rock rose to the surface, cooled and became the crust. The oldest known Earth rocks to date are approximately 3.8 billion years old. Meteorites and lunar rocks have been found to be approximately 4.5 billion years old.

5. Archaean Era • The Archaean period was a time of continent-building and the first stages of early life. In fact, 70% of our continental land masses are formed around cores of rock, or shields, that date from this period. • The atmosphere was perfect for bacteria. It was filled with ammonia, methane, and hydrogen.

6. Proterozoic Era • Plate Tectonics begins…the plates were thinner and the magma was hotter so they moved faster. Collisions and fractures were more frequent. • Early plants helped develop an oxygen-rich atmosphere. Because of this, eukaryotic cells developed. • Toward the end of the Proterozoic, multi-cellular algae and the first multi-celled animals were the result.

7. Paleozoic Era • Consists of the following periods • Cambrian • Ordovician • Silurian • Devonian • Carboniferous • Permian

8. Cambrian Period • The climate at the beginning of this period was cold, but over time the climate in all parts of the Earth grew warmer. This made the seas a good place for many species to live. The continents were still forming. They were mostly barren rocks. The land had no plant or animal life on it yet. • During the Cambrian Period there was an explosion of life forms. Most of these were in the water. Many animals with no backbones lived in the shallow seas. These animals were invertebrates.

9. Cambrian Period • The Cambrian Period began with an explosion of life forms. It ended in a mass extinction. Advancing glaciers would have lowered the temperature of the shallow seas where so many species lived. Changes in the temperature and the amount of oxygen in the water would have meant the end for any species that could not adapt.

10. Ordovician Period • Gondwana was a huge supercontinent during the Ordovician Period. • During the first parts of the Ordovician the climate was fairly warm. The land uplifted and the continents moved around. When Gondwana stopped its movement over the South Pole, glaciers formed. This caused the sea level to drop and the climate to change. These changes led to a mass extinction at the end of the Ordovician Period.

11. Silurian Period • The climate was much warmer during the Silurian Period. This caused the glaciers to melt and the seas to rise. Even though the sea level was rising, there were places where the land was slowly rising as well. This was due to mountain building as the continental plates collided. In these places the seas moved away from the coasts or evaporated from the shallow areas. This left salt deposits. Plants that had lived in the coastal water had to adapt to life on land or die. • New Life= coral and jaw-less fish

12. Devonian Period • Two continents would collide to form the supercontinent Pangaea in the Permian Period. • Plants cover the land • Insects and other animals find homes on the land • Fish with jaws developed, so did sharks • Devonian Period ended with another mass extinction that hurt water species more than those on land.

13. Carboniferous Period • New plants developed in the warm, humid climate and swampy conditions of the Carboniferous Period. Large trees covered with bark and huge ferns grew in the middle Carboniferous swamps. The plants gave off so much oxygen that the air had much more oxygen in it. This allowed plants and animals to reach sizes that are not known in today’s atmosphere. When the huge trees and ferns died, they fell into waters that did not have bacteria to help them decompose. These plants formed peat beds. Eventually, with the weight of layers and layers, these peat beds turned to coal.

14. Permian Period • For most of the Permian, life on Earth was much like it had been in the Carboniferous. Temperatures were cooler because the continent of Pangaea was moving northward. Mountains were forming as the supercontinent Pangaea moved. • Conditions become dry and plants adapt to it. • The Permian Extinction was largest mass extinction that had ever occurred. No extinction since has killed so much of the life on the planet. In the seas, 90 to 95 percent of the species went extinct or were severely harmed.

15. Mesozoic Era • Consist of the following periods: • Triassic • Jurassic • Cretaceous

16. Triassic Period • It had a special climate because of the way the land was placed on the Earth. At the beginning of the Triassic, the land was all together in one supercontinent, Pangaea. It straddled the equator, so the climate was warm. • Pangaea started to break up. • The most important development was happening to the reptiles. These animals would dominate the land, sea and air throughout the Mesozoic Era.

17. Triassic continued • The first dinosaurs were evolving. The dinosaurs were different from the reptiles. 1)First, they were warm-blooded. This means the temperature of their blood was kept constant inside their body instead of changing with the outside temperature. 2) Their bone structure was different in the hips, legs and hands.

18. Triassic continued • Another land animal developing around the same time as the dinosaurs were the mammals. These mammals were very small. They weren’t very important until millions of years later in the Cenozoic Era. • Tree-ferns and lycopods could not live in the dry climate of the Triassic Period. • Instead, the conifers and ginkgos survived the Permian extinction and developed during the Triassic. The evergreen plants were much more able to cope with the dry climates.

19. Triassic continued • The extinction that marked the end of the Triassic Period seemed small compared to the one that ended the Permian Period. Only about 20% of life in the oceans and on land died out completely. The species that were affected came back with strength and would soon dominate the world of the Jurassic and Cretaceous Periods.

20. Jurassic Period • Pangaea continued to split apart during the Jurassic. • The climate was warm and stable. Many types of animals and plants developed. The numbers of different species increased greatly during the Jurassic Period. • As the land pulled apart, the seas rose. Warm shallow seas again covered parts of Laurasia (North America and Eurasia). With the warm seas touching the land, the climate became more humid and tropical. Plants grew thick and tall.

21. Jurassic Park FYI • There are many misunderstandings about dinosaurs. Movies and TV have led us to believe many things that aren’t really true about how and when dinosaurs lived. For example, the movie Jurassic Park included Tyrannosaurus Rex and Velociraptors as some of the “star” dinosaurs. In fact, neither T-Rex nor Velociraptors existed until long after the Jurassic Period was over.

22. Jurassic continued • Mammals continued through the Jurassic Period. They remained small. Many different species developed, but the mammals were still not playing a large part in the day-to-day life of the Jurassic. • There is a minor mass extinction at the end of the Jurassic Period.

23. Cretaceous Period • The changes to the continents continued in the Cretaceous Period. Laurasia and Gondwana continued to move apart. • In Gondwana, South America and Africa broke apart. • The most famous dinosaur of all, the Tyrannosaurus rex, finally came along during the Cretaceous Period. They ruled the land at the end of the Cretaceous Period.

24. Cretaceous continued • The most important development of the Cretaceous Period was the growth of flowering plants. Before this, most of the trees had been gymnosperms or plants with cones. Now trees began to produce flowers. • With flowers came many insects including butterflies, ants, termites and bees.

25. Mammals continued to exist during the Cretaceous Period, but they were not very important. These were tiny creatures compared with the giant dinosaurs.

26. KT Event • There seems to have been a major event that caused the mass extinction at the end of the Cretaceous Period. It is called the KT event. • A popular theory is that a meteor hit the earth in the Gulf of Mexico off the Yucatan Peninsula. This caused many geologic activities. Volcanoes erupted. Clouds, smoke and dust covered the skies keeping the sun’s light away from the planet for years. This would have caused huge changes in the climate and vegetation.

27. Major Extinction • The KT event caused the extinction of more than 70 % of the species that lived in the oceans and 15% of the species on land. In fact, all land animal species over 50 pounds seem to have become extinct. Nearly all dinosaurs became extinct at this time.

28. Cenozoic Era • Cenozoic Era consists of 2 Periods, but each is broken down into smaller epochs. • Paleogene • Neogene

29. Paleogene Period • The beginning of the Paleogene Period was very warm and moist compared to today’s climate. Much of the earth was tropical or sub-tropical. Palm trees grew as far north as Greenland! • By the end of the Paleogene, during the Oligocene Epoch, the climate began to cool.

30. Geographic Events in the Paleogene • Oligocene Epoch • Australia separates from Antarctica • India crashes into Asia creating the Himalayan Mountains • Antarctica is covered by glaciers • Sea levels are low • Eocene Epoch • North America and Europe separate • Paleocene Epoch • Europe and North America are joined together • Australia is joined with Antarctica • India is not yet connected with Asia • The Atlantic Ocean is small because South America and Africa have just separated

31. Mammals appearing during Paleogene • Oligocene • Dogs • cats • pigs • toothed whales • Eocene • bats • elephant ancestors • whales • eohippus-the first horse • Paleocene • The condylarths-ancestors of mordern hoofed herbivores • rodents • the first primates

32. Neogene Period • The Neogene Period was a time of big changes for the earth. The climate became cooler and drier. Grasslands replaced forests. The animals had to adapt to these changing conditions or face extinction. • Drop in sea levels opened up land bridges between continents. This allowed animals to migrate between continents.

33. Neogene continued • South America moved to the north. By the Pliocene Epoch it merged with North America forming the Isthmus of Panama. Armadillos, porcupines, ground sloths and opossums migrated from South America to North America. Dogs, cats, bears, and horses from North America crossed into South America.

34. Neogene continued • Many of the areas that had been covered by forests were changing to grasslands. Grasses were better suited to the cool dry weather. • Changes in the plants meant that the animals had to adapt or die. • New predators evolved for the grassland environments of the Neogene Period. The grazing animals could run fast. Predators had to adapt or go hungry.

35. Neogene continued • Sharks developed new species. One of these new sharks was Megalodon. It appeared first in the Miocene Epoch about 16 million years ago. Megalodon was the largest of all the sharks.

36. Neogene continued • By the end of the Pliocene Epoch the earth was locked in an Ice Age. There were many reasons that this happened. The lower sea levels, new mountains and shifting ocean currents all contributed. Ice caps grew over the polar regions. They stretched far beyond their present locations. Glaciers, growing from the ice caps, reached down as far as Ohio in the United States.

37. Quaternary Period • The Quaternary Period began with an ice age about 1.8 million years ago. It is often called the Age of Humans. • It continues up to the present time and is the period that we live in. • During the quaternary period the positions of the continents were much the same as they are today. What has changed during this time is the climate.

38. Quaternary continued • There is a reason the polar ice advances and retreats. It isn’t random. The variations are because of changes in the Earth's orbit. These are called Milankovitch cycles. The last major glacial advance was about 18,000 years ago. Some scientists say that we are still in an ice age and the current warming trend is just an interglacial period or temporary retreat of the polar ice.

39. Quaternary continued • For us, the most important development of the Quaternary Period is the development of the hominids: Humans. From the first primates in the Tertiary Period to modern man, the hominid species has evolved amazing abilities. • Their larger brains allowed a level of thought and feeling that was, and is, unique among the animals