Essay on Extinction Event and Period

Submitted By isadorable96
Words: 1926
Pages: 8

Our planet has changed a great deal in its 4.6 billion years of life. Earth’s climate, tectonic plates, and organisms are constantly evolving as time goes on. 4.6 billion years is a very long period of time to study in-depth and it would be too confusing to organize all the events in earth’s geological and biological history into one division of time, so scientist have split them up in order to better organize and understand how earth was like at particular periods of time. We’ll start at the beginning, 4.6 billion years ago, at the beginning of the Hadean Eon. The inspiration for the name of this eon came from the conditions of earth at the time. Earth was nothing more than a large magma ocean of molten rock material. It was very hot and unable to sustain life, therefore it earned the name Hadean, originating from the Greek god of death and the underworld, Hades. These are the reasons why I also chose to use an illustration of an ocean of magma, and also a skull and crossbones to represent this eon on my poster. There were no fossils of living organisms from this eon, therefore it hasn’t been divided into further sections of time. Directly following the Hadean Eon came The Archean Eon, which began 3.8 billion years ago. This eon is know best for its high amounts of volcanic activity, hence the illustration of a volcano on my timeline. There were no large continents on Earth at this time, but there were small fragments of continents dispersed across the globe. These mini continents were the “seeds” of larger continents that were to come later on. One significant detail about the Archean Eon was that it was the period of time where life first emerged on planet Earth. During this time, oxygen was not present in Earth’s atmosphere. Instead, the toxic gases methane and ammonia, byproducts of volcanic activity, filled the air. The only life forms on earth at this time were microscopic bacteria that could survive without the presence of oxygen in Earth’s atmosphere. After the Archean Eon ended 2.5 billion years ago, came the beginning of the Proterozoic Eon. I chose to draw a supercontinent and simple bacteria to represent this eon because during this time on earth, massive continents had just began to develop and bacteria were beginning to evolve with more structural complexity. Rodina, a supercontinent that included almost one-hundred percent of the land on Earth at the time, formed during this eon. Scientists believe that earth was completely covered in ice due to the fact that large glacial deposits have been found dating back to this eon. During the Proterozoic, approximately one billion years ago, trace fossils of simple single, and multi-celled eukaryotes, with complex organelles, have been found. The eon we are currently living in today is the Phanerozoic Eon, which started approximately 542 million years ago following the end of the Proterozoic. The beginning of this eon began with explosion of biodiversity, as many new creatures emerged on Earth for the very first time. Even though it is the youngest of the four eons, the Phanerozoic Eon had had the most variety of life forms, therefore it has been divided into twelve periods of time. The first period of the Phanerozoic Eon was the Cambrian Period, beginning 542 million years ago. This is where metazoans, or multi-celled organisms, began to appear. These organisms included worms, jellyfish, coral, Bilaterians, and the very strange and still poorly understood creatures of the Ediacaran family, like the infamous Hallucigenia. I chose to use a trilobite to represent the Cambrian Period because it was a very common anthropoid swimming in the vast oceans during this time. During the Cambrian Period most of earth’s land was located below the equator in the Southern Hemisphere. Though there was land present during this period, there were no existing land organisms. The next period was the Ordovician Period that began 488 million years ago. This period saw the origin…