Week Eight Notes-Geology G-104
Week Eight Notes-Geology G-104 GEOL-104 20584
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This 2 page Class Notes was uploaded by Ashley Hughes on Wednesday March 11, 2015. The Class Notes belongs to GEOL-104 20584 at Indiana University taught by Laura Wasylenki in Spring2015. Since its upload, it has received 98 views. For similar materials see Evolution of the Earth in Geology at Indiana University.
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Date Created: 03/11/15
3315 G104 I What types of rocks can be used for relative dating 0 Limestone Shale Granite Metamorphic schist Basalt 0 How were named periods in the geologic timescale defined 0 Randomly by old white men with beards O Boundaries were placed where each big ood shows up in the rock record 0 Boundaries were placed where many fossil species disappeared all at once 0 Boundaries were placed regularly every few million years 0 Inheritance of characteristics from parents 0 O O O 0 Random variations among offspring I Struggle to survive to reproduce natural selection I Gradual change of morphology and species over time 0 Early strategies for getting the age of the Earth 0 Salt content in sea water I Assume salt is constantly added over time I 100 million years 0 Sediment accumulation I Thickness I Assuming constant rate of accumulation ie no erosion movement etc not good I 24 million years 0 Temperature of the center of the Earth I Same rate same temperature completely at the beginning I Time to cool off I 2040 million years I 87Rbl87sr rubidiumljstrontium O Neutron turns into proton O Radioactive decay O 484 billion years halflife of rubidium 87 I Length of ip Probability ratio 0 3515 Age1decay constantlogarithimdaughterparent 1 0 Equation describes exact shape of behavior 0 The decay constant is directly related to the halflife 0 Each kind of radioactive isotope has its own decay constanthalf life suppose you analyze an ancient rock and exactly two halflives have gone by Halflife is 150 million 0 300 million years old RbSr dating is good for really old rocks 0 Very long halflife KAr dating is good for medium aged rocks Carbon dating is good for young rocks and archeological items Choose a rock or mineral that contained the parent when it formed 0 Kfeldspar crystal takes up Rb at time it crystalizes from magma but little or no Sr 0 Amainis of Rbg7 and Srg7 tell us how long since the crystal formed What can we date this way 0 Igneous rock 0 Sedimentary rock Put relative dating and absolute dating together to put numbers on the times cave Relative dating sedimentary So how old is the earth 0 Uraniumlead age456 billion years Oldest mineral year dated 44 billion years old dating done in 1999 0 So we have a 456 billion year old earth How did we get here 0 Observation 1 a bunch of planets orbiting around a star in a plane in the same direction 2 nebula are full of stars like ours and the stars have stuff around them Some of the stars have a big blob of gas around them Some have a attened disk of gas Some have a lot of small solid and gaseous bodies in a plane 0 Some have a handful of planets revolving around the star Chandrites O Accredited to making rocky planets 0 Bulk composition of rocky planet OOOO