GEEslidesSet2 27Jan2010

GEEslidesSet2 - GEOLOGICAL FUNDAMENTALS ROCK FORMATION Igneous rock created from molten material Ex from lava Sedimentary rock deposition and

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Unformatted text preview: GEOLOGICAL FUNDAMENTALS ROCK FORMATION Igneous rock -- created from molten material. Ex from lava Sedimentary rock -- deposition and solidification of sediments. Most fossils are found in sedimentary rock. Metamorphic rock -- results from the transformation of igneous or sedimentary rock under high pressures and temperatures. PLATE TECTONICS The outer layer of the earth is made up of plates that move across the face of the planet. The maximum velocity is about 5-10 cm per year. Not fully accepted until the 1960s. GEOLOGICAL FUNDAMENTALS MEASURING GEOLOGICAL TIME Astronomers think the universe is about 14 billion years old. The solar system and the Earth are about 4.6 billion years old. The oldest known rocks on Earth are about 3.8 billion years old. Living things existed starting at least 3.5 billion years ago. The first evidence of metazoan animal life is about 800 million years old. THE AGE OF THE EARTH ANALOGY If the age of the Earth is represented by a single year : • First life appears in late March. • First marine animals debut in late October. • Dinosaurs become extinct and the mammalian radiation begins on December 26. • The human and chimpanzee lineages diverge about 13 hours before midnight on December 31. • Christ is born about 13 seconds before midnight on December 31. SOME DATING CONCEPTS RELATED TO FOSSILS Igneous rocks can be dated using techniques based upon the decay of radioactive elements (e.g., Potassium-Argon dating), because radioactive isotopes decay at known, constant rates. Carbon-14 dating can be used on organic material up to about 50,000 years old. You have to use other tools if older. SUPERPOSITION-- With some detectable exceptions, younger rocks are on top of older rocks. STRATIGRAPHIC COLUMN-- The local series of STRATA , or sedimentary layers. These simple principles can be used to date most fossil- containing layers of rock. HOW GOOD IS THE FOSSIL RECORD? It is “dreadfully” incomplete. Organisms without hard skeletons don’t fossilize well. Best fossil records have been left by marine invertebrates with hard skeletons. The gradual origins of species and higher taxa have not been documented for the most part. Why have the origins of higher taxa not been documented? HOW GOOD IS THE FOSSIL RECORD? Many kinds of organisms rarely leave remains, because they are completely consumed by other organisms. Sediments usually form only sporadically g& & at a given location. Fossil-bearing sediments must solidify into rocks and persist for millions of years. The rock must be exposed and accessible to paleontologists. g & & & There is little reason to suppose that the evolutionary changes in which we are interested occurred at the few localities of a time interval that actually allowed fossilization. HOW GOOD IS THE FOSSIL RECORD?...
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This note was uploaded on 04/09/2010 for the course BIOL 214 taught by Professor Pepper during the Spring '08 term at Texas A&M.

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GEEslidesSet2 - GEOLOGICAL FUNDAMENTALS ROCK FORMATION Igneous rock created from molten material Ex from lava Sedimentary rock deposition and

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