3Geologic Time ScaleChart of Earth’s history showing events, time units, & agesEra: the four largest subdivisions of the geologic time scale – Precambrian, Paleozoic, Mesozoic, CenozoicPeriod: subdivisions of eras on the geologic time scaleEpoch: subdivisions of periods on the geologic time scale – ONLY in the Cenozoic
5Traces from our pastIndex Fossils: a fossil of a species that existed briefly and was widespread geographically, used in determining the relative age of rock layers (i.e. trilobites)Fossils and Ancient Environments: fossils can be used to determine what the environment of an area was like long ago.
6Traces from our pastFossils: the remains or traces of a once-living organism preserved in rock.How fossils form:organisms have a better chance of being preserved if they have hard parts (bones, shells, teeth, or wood)usually found in sedimentary rocks
7Petrified RemainsPetrified Remains – plant or animal remains that have been turned to rock; this happens when minerals carried in groundwater replace the original material.
17Age Dating TechniquesRelative Dating: determining the order of events and the relative ages of rocks by examining the positions of rocks in layers
18Age Dating TechniquesRelative Dating – another good diagram
19UniformitarianismIn 1795, James Hutton described a ‘new concept’ stating that:The geologic processes now at work were also active in the past.The present physical features of Earth were formed by these same process, at work over very long periods of time“the present is the key to the past”
20Relative DatingLaw of Original Horizontality: sediments are deposited in a horizontal fashion
21Relative DatingLaw of Superposition: in layers of undisturbed rock, the oldest are on the bottom, and rocks become younger toward the top
25Relative DatingLaw of Included Fragments: pieces of one rock found in another rock must be older than the rock in which they are found
26Relative DatingCorrelation: the matching of rock layers from one area to another to establish a relative date
27Relative DatingUnconformity: one or more missing layers in a sequence of rocks, this is the result of gaps in the time/rock recordangular unconformity – tilted rock layers meet horizontal rock layers, this indicates layers are missing and there is a gap in the time recorddisconformity – the top rock layer is eroded before the next layer can be deposited causing a gap in the time record
33Age Dating TechniquesAbsolute Dating: determining the age of rocks using the radioactive decay of atoms.Radiometric Dating: an Absolute Dating method that uses the rate of decay of radioactive isotopes in rocks.
34Age Dating TechniquesRadioactive Decay: the decay of an atom of one element to form another element, occurring when an alpha particle or beta particle is expelled from the original atom (Ex. parent atom (K) decays to daughter product (Ar))Half-Life: the time it takes for half of the parent atoms of an isotope in an object to decay into the daughter product (K-Ar = 1.3 billion years)
35Age Dating TechniquesTree rings – counting the number of rings on a cross section of a treeRadio-Carbon dating – the radioactive carbon isotope used for dating organic material:Carbon 14 decays to Carbon 12The ‘half life’ of Carbon 14 is 5700 years…Half life – how long it takes for half of the material to decay
37Precambrian Time from 4.6bya to 545mya makes up ~90% of Earth’s historyvery little is known about fossils from this periodcyanobacteria appeared around 3.5 byaresponsible for oxygen andindirectly for ozone inthe atmosphereinvertebrates developedat end of era
38Paleozoic Era: 545mya to 245mya began when animals developed hard parts that could be fossilizedlife moved from ocean to landend signified by mass extinction probably caused by formation of PangaeaEarly - “Age of the Invertebrates”Late – “Age of the Plants”Paleozoic Era:
39Mesozoic Era245 mya to 66 myaLaurasia & Gondwanaland developed from the break-up of PangaeaReptilian eggs developed a hard shellDinosaurs evolved during the Triassic and dominated during the Jurassic and Cretaceous periods
40Mesozoic Era (cont.) “Age of the Reptiles” (Dinosaurs) Mammals appeared during the TriassicBirds appeared during the JurassicAngiosperms appeared during the CretaceousEnd signified by mass extinction“Age of the Reptiles” (Dinosaurs)
41Cenozoic Era 66mya to present Increased tectonics created the Alps, Himalayas, and the AppalachiansGlobal temperature dropMammals evolved anddominatedHomo sapiens emerged500,000yrs. ago“Age of the Mammals”
43Evolution Organic Evolution: gradual change in life-forms through time Species: group of organisms similar to each other and that typically reproduce only with each other.Natural Selection: natural process by which some organisms survive and reproduce because they have traits favorable to survival in an environment, while others die out because they lack those traits
44EvolutionEndangered: describes a species that has a small number living and thus in danger of dying outHabitat: any place where organisms live, grow, and interact
45General Related Facts – (the amazing impact humans have had) Four years ago 19,836sq. km. of Amazon rainforest was destroyedMore than 80% of all deforestation of the Amazon has occurred since 1980More than ¼ of all pharmaceuticals come from rainforest plants
46General Related Facts – (the amazing impact humans have had) only 22% of Earth original forest coverage remains…..Western Europe lost 98% of its primary forests;Asia 94%;Africa 92%;N. America 66%;S. America 54%