Exam 3 - o Introduction to Paleontology o Fossils made when...

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Unformatted text preview: o Introduction to Paleontology o Fossils made when things die 99.9% died without leaving a trace- very rare for fossils to form Bones with high mineral content will survive long enough to get buried by sediments and theres a chance that organic material in bones will be replaced with inorganic materials & become a rock Teeth have better chance than bonesmore mineralized v. Soft tissues have little/no chance of fossilizing Overtime, things get buried- hillsides are constantly eroding Can be buried anywhere Our dirt is from the rockies o Taphonomy: study of how fossils are made/form o Preservation determined by surroundings & chemicals- bird feathers Nariokotome boy- homo ergaster- preserved the sinus cavity (interior) Pompeiionly the exterior was preserved o Deformation- weight & pressure of the ground has effect on fossils- Chad Skull hominid sahelanthropus tchadnesis Ground is always shifting, so fossils can become bent/tweaked o Dmanisi, Republic of Georgia- found rhinoceros fossils by complete luck Dmanisi people kept stuff cool by digging cellars to store things Led to discovery of most productive hominid site in the world o Olduvai Gorge- African Savanna- land & erosion covers stuff up East Africa is being split into 2 (geologically speaking) and tears in ground are causing layers to be exposed Find something small- set up mini excavation o How old is it? Relative Dating: includes techniques were you get a general idea of how old something is, Law of Superposition: the lower an item is discovered, the older it is (but geographic layers can get tilted up over tiem) Flourine: the larger amount of fluorine in a fossil, the older it ishugely variable from site to site Biostratigraphy: the use of animal & plant fossils as a comparative way to date fossils Paleomagnetism: the north pole is magnetically north, but polarity has switched throughout history and the directionality is preserved in iron/metal elements o Chronometric/Absolute Dating: take advantage of the fact that the earth is full of radioactive elements 14 C Dating: has 8 neutrons in nucleus & is unstable, so it breakdowns into 14 N, and is absorbed by plants, which is eaten by animals and then eaten by animals who eat those animals (everyone emits 14 C) Takes about 5730 years for half of 14 C to decay= half-life Rate of emission tells you how old something because the rate decreases with half-lifes 14 C is only good for fossils dating back 40,000 years 40 K-Ar- 1/100 th % of potassium in the world is unstable- it has 40 neutrons- it breaks down into argon Potassium very common in igneous/lava rocks The more argon, the older the sample Amount of argon relative to amount of potassium tells us how long its been since lava flowed Basalt: once-flowing lava More recent version is argon-argon dating Good for anything older than 100,000 years Half-life of 40 K is 1.28 billion yearsK is 1....
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Exam 3 - o Introduction to Paleontology o Fossils made when...

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