Biology of the Earth - Chapter 11 Simple History of Earth...

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Unformatted text preview: Chapter 11 Simple History of Earth The geological biography of Earth from its birth , 4.57 billion years ago, to the present simply put: Continents came into existence and have migrated across the globe ever since Mountain-building events occurred Climate and sea level have changed through time Life has evolved Abbreviations: Ga - billion years ago Ma - million years ago Ka - thousand years ago http://paleo.cortland.edu/tutorial/Timescale/timescale.htm Geologic Time Scale 1 st vertebrates, fish Land plants spread over land surface Amphibians appeared Reptiles appeared Dinosaurs appeared; and small mammals Dinosaurs disappeared MESOZOIC: AGE OF DINOSAURS Diversification of mammals CENOZOIC: AGE OF MAMMALS Birds appeared Hadean Eon The mysterious time interval between the birth of the Earth and 3.80 Ga From the Greek word Haedes- the god of the underworld Hadean History: Earth formed within 30 million years of the time when the Suns nuclear furnace began Earth formed by the accretion of planetesimals As planets grew, collection and compression of matter into a dense ball generated much heat; meteorite collisions and radioactive decay produced even more heat within the planet Hadean History Earth became so hot that it partially melted, occurring around 4.5 Ga The planet underwent internal differentiation : Gravity pulled molten iron down to the center of the Earth, where it accumulated to form the core The mantle, composed of ultramafic rock, remained as a thick shell surrounding the core Internal differentiation process may have occurred relatively quickly, generating enough heat to make the Earth even hotter Earths Structure The Earths interior consists of a series of concentric layers: CRUST : not very dense, composed of rocks like granite, basalt, and gabbro MANTLE : lies below the crust CORE : very dense center Earths Structure Earths CORE is differentiated into 2 regions: 1. Inner Core : solid iron at temperatures higher than the melting point of iron remains solid due to the extremely high pressure 5,155 to center at 6,371 km Consists of an iron alloy (iron mixed w/lesser amounts of oxygen, nickel, silicon, or sulfur) 1. Outer Core : molten metallic iron with a lighter density 2,900-5,155 km deep http://www.seismo.unr.edu/ftp/pub/louie/class/100/interior.html http://www.phschool.com/atschool/science_activity_library/images/earths_interior.jpg Earths Structure MANTLE : Forms a 2,885-km-thick layer surrounding core Largest part of the Earth, by volume...
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This note was uploaded on 04/01/2012 for the course GEOLOGY 1122 taught by Professor Sethrose during the Fall '10 term at Georgia State University, Atlanta.

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Biology of the Earth - Chapter 11 Simple History of Earth...

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