Table Of Contents page

Introduction..............5

chapter 1...................6

Chapter 2...................8

Chapter 3...................10

Chapter 4...................13

Conclusion.................14

Glossary.........................16

Work Cited...................17

Introduction:

The Introduction of our book introduces the four major geological eras that shaped our world today.

• chapter 1:

The Precambrian era began about 4.5 billion years ago and ended about 4 billion years later. First is started with the formation of the earth from dust and gas orbiting the Sun. The Precambrian era Makes up 87% of earth's history. Also Organisms developed sponges and jellyfish and developed photosynthesis.

Chapter 2

The Paleozoic Era, which ran from about 542 million years ago to 251 million years ago , was a time of great change on Earth. One major event was the Cambrian explosion which was an event approximately 541 million years ago in the Cambrian period when most major animal phyla appeared in the fossil record. It lasted for about 20–25 million years. This was the time when plants evolved, though they most likely did not yet have leaves or the vascular tissue that allows modern plants to siphon up water and nutrients. There was also a Mass extinction 90% marine and 70% land. 

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Chapter 3

The Mesozoic Era is an interval of geological time from about 252 to 66 million years ago. At the start of the Mesozoic, the continents were all joined together forming one large continent called Pangaea. During Mesozoic time, they pulled apart from one another. Continents move due to plate tectonics. Also Much larger and more complex organisms such as dinosaurs, mammals, and birds developed during this era. There was also a mass extinction. During the last part of the Mesozoic the climate warmed very much. Earth was several degrees warmer than it is today. There was much less variation in temperature between the equator and the poles at this time.