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Geol 1003 Test 2

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GEOL 1003
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Wednesday February 20Radiometric decay is constantit doesnt change with any conditions therefore the ratio of parent to daughter isotopes is a function of timeHalflivesthe amount of time that it takes for HALF of the parent isotopes to change into the daughter isotopesAfter so many halflivesRatio of Parent to Daughter111214343187841161516Table 62 Shows some common isotopes used for radiometric datingA good range for these is from around 15 halflive to 5 halflivesThere will be a test question about this so look at the tableHe will ask which isotope you should you use for something of a specific ageIsotopesHalfLifeRubidiumStrontium488 billion yearsThoriumLead14 billion yearsPotassiumArgon13 billion yearsUraniumLead7 billion yearsCarbonNitrogen5730 yearsIf you look between two igneous rocks and find a sedimentary formation of unknown age you can infer that it must be older than the rock it is under and younger than the rock it is aboveEvent DepositsMarker Bedsbeds laid down in a short time over a large areaThis helps ussee correlation between beds far away from each otherImpact Layerlayer of ash from the meteor crash that supposedly wiped out all life on the EarthWe also see transitions in sedimentary rocks with a change in the level of the oceans transgression to regression or vise versaThis sort of change is seen worldwide but just in one areaChange in Sea Level1Eustatic EventsEustatic changes in sea levelIn the past 65 million years the sea level worldwide used to be much much higher by 150300 mHowever we are now higher than 2000015000 years agoThis period was known as the LGM last glacial maximumIce was piled up on the continents so sea level was about 100120 m lowerIce meltingcauses high frequency in sea level changesA global sea level rise doesnt necessarily result in a transgression in all areasA global change in sea level is known as a Eustatic changeExIf the global sea level drops but the land in a certain area is sinking faster sea level in that area would actually riseFor the opposite if sea level rises globally and the land also rises sea level in that area would dropIn areas like Scandinavia ice will melt and sea level will rise but due to isostacy the land will rise due to the weight of the ice being removedPlate tectonics will also change sea levelsThis however will not have as high of a frequency and will occur over millions of yearsFriday February 22 What causes Eustatic changes in Earths historyExpansion and contraction of continental glacierso100 m in a few tens of thousands of yearsChanges in volumes of midocean ridgeso10 m in 1 million yearChapter 7Evolution and the Fossil RecordUniversal common decentis the hypothesis that all living terrestrial organisms are genealogically related All existing species originated gradually by biological reproductive processes on a geological timescale Modern organisms are the genetic descendants of one original species or communal gene pool Charles Darwin1Showing that species had evolved in nature Different from Cuviers viewaSloths and armadillos ONLY in AmericabIsthmus of PanamacGalapagos Islands Tortoise and FinchdAnatomical Evidencehomology vestigial organs2
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