The Age of the Earth.docx

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Department
Earth & Environmental Sciences
Course
EESC 1175
Professor
Alan Kafka
Semester
Spring

Description
TheAge of the Earth How old is the Earth? • James Ussher o Age of the Earth = 6,018 years old  Based on biblical events in the Old Testament, he found that the world was crated on October 23 , 4004 BC at 9 a.m. • Scientists’calculations o Age of the Earth = 4.6 billion years old  Based on evidence found in rocks and radiometric dating Rocks and Geological Time Scale • Oldest Rocks = 4.0 billion years old • Oldest Minerals = 4.5 billion year old • 540 million years ago (“Pre-Cambrian”)  beginning of life o The first evidence of fossilized life within rocks • Time Scale: o 14 billion years ago  The Big Bang o 3.5 to 4.0 billion years ago  earliest form of life o 100,000 years (more or less)  modern human life Anthropocene = most recent period of time in Earth history (past few hundred years) in which humans have significant global impact on the planet • Paul Crutzen Holocene = last 10,000 years since the end of the last IceAge Geologic Time: • Geochronology = the science of determining the age of rocks • Nicholas Steno (1669)  studied strata rocks to determine age o Principle of Superposition: in any sequence of “undisturbed” strata of sedimentary rocks, the oldest layer is on the bottom and the higher layers and younger o Sedimentary Rocks = rocks formed from weathered products of pre- existing rocks (sediments) that have been transported, deposited, and lithified  converted into rock • Principle of Uniformitarianism: the physical, chemical, and biological laws that operate today have also operated in the geologic past • Sequence of Geologic Events 1. Deposition 2. Folding and Uplifting 3. Erosion 4. Subsidence and Renewed Deposition RelativeAge vs.AbsoluteAge • Absolute age of the Earth  amount of time since the Earth solidified o When did the Earth cool and solidify into its present state from the hot, molten, rocky material it used to be? Methods to Estimating theAge of the Earth  Fossils and evolution  Rates of deposition of sediments  Cooling of the Earth from a molten state  Radiometric Dating Principle of Parsimony • Oscam’s Razor • Fossils  remains of ancient life o Charles Lyell (mid-1800s): used evolution to estimate absolute ages of rocks  He needed to find a natural process that leaves a tangible record in the rocks
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