Presentation on theme: "Dating Techniques Bell Ringer: Put the letters in order from earliest event to latest event."— Presentation transcript:
1Dating TechniquesBell Ringer: Put the letters in order from earliest event to latest event
2Dating TechniquesBell Ringer: Put the letters in order from earliest event to latest eventHow did you put these pictures in order?How can scientists determine how old geologic formations are, such as the grand canyon?
4Dating TechniquesKey Concept 1: rocks record geological events and changing life forms of the pastKey Concept 2: We have learned that Earth is much older than anyone had previously imagined and that its surface and interior have been changed by the same geologic processes that continue todayErosionPlate tectonicsEarthquakesvolcanoes
5Dating TechniquesKey Concept 3: Uniformitarianism - the forces and processes that we observe today have been at work for a very long timeTo understand the past we must first understand the present-day processes and their resultsThe surface of the Earth is constantly changing, but not necessarily on the human timescale
6Relative DatingGeologists can tell how old certain formations of the earth are based on the age of other things around themKey Concept 4: Relative dating tells us the sequence in which events occurred, not exactly how long ago they occurred
7You can say that layer B is older than layer C, but you cannot say exactly how old either of them areYoungest: EADCOldest: B
8Relative DatingThere are 4 laws used in relative dating of geologic formationsLaw of superpositionPrinciple of original horizontalityPrinciple of cross cutting relationshipsLaw of Unconformities
9Relative DatingKey Concept 5: the law of superposition states that in an undeformed sequence of sedimentary rocks, each bed is older than the one above it and younger than the one below itYoungestOldest
10Relative DatingKey Concept 6: The principle of original horizontality means that layers of sediment are generally deposited in a horizontal pattern
11Relative DatingKey Concept 7: The principle of cross-cutting relationships states that when a fault cuts through rock layers, or when magma intrudes other rocks and crystallizes, we can assume that the fault or intrusion is younger than the rocks affected
12Relative DatingKey Concept 8: an unconformity represents a long period during which deposition stopped, erosion removed previously formed rocks, and then deposition resumed
13Relative DatingKey Concept 9: An angular unconformity indicates that during the pause in deposition, a period of deformation (folding or tilting) and erosion occurred
14Relative DatingKey Concept 10: To develop a geologic time scale that can be applied to the entire Earth, rocks of similar age in different regions must be matched up. This is called correlation.
17Bell Ringer: How could you more accurately relatively date this formation? What information would you want?
18Ms. V needs your helpI need help settling an argument…my dad and I don’t remember how long ago the movie Madagascar came out.We are big Phoenix Suns fans so wecompared the amount of time to theyear certain players were on thePhoenix Suns
19Ms. V needs your helpMy dad thinks the movie came out the same year that Shawn Marion, Amar’e Stoudemire, and Kevin Johnson all played togetherI think it was the year that Shawn Marion, Amar’e Stoudemire, and Steve Nash all played togetherHow can we settle this argument?
20Ms. V needs your help What if I gave you something like this? Name Years197019751980198519901995200020052010Paul WestphalShawn MarionAlvan AdamsConnie HawkinsTom ChambersAmar'e StoudemireKevin JohnsonWalter DavisSir Chrales BarkelySteve Nash
21Ms. V needs your helpWhat if we then filled it in with the years these players all playedNameYears197019751980198519901995200020052010Paul WestphalShawn MarionAlvan AdamsConnie HawkinsTom ChambersAmar'e StoudemireKevin JohnsonWalter DavisSir Chrales BarkelySteve Nash
22Ms. V needs your helpLooking at the table we can determine that the year Shawn Marion, Amar’e Stoudemire, and Steve Nash all played together was 2005So…using this “relative dating” technique we can conclude that Madagascar came out in 2005
23The same principle can be applied to geological relative dating How does the Phoenix Suns relate to earth science?Using the years of the phoenix suns players we were able to determine the relative age of the movieThe same principle can be applied to geological relative datingThe location of fossils within geologic formations can also indicate relative age of different layers.
24Relative Dating - Fossils The longer a species has lived, the better chance it has of being fossilized and preservedKey Concept 11: The type of fossil that is formed is determine by the conditions under which an organism died and how it was buried
25Relative Dating - Fossils Key Concept 12: A fossil is the remains or traces of an organism preserved from the geologic pastKey Concept 13: Two conditions are important for preservation: rapid burial and the possession of hard parts
27Relative Dating - Fossils Key Concept 14: The principle of fossil succession states that fossil organisms succeed one another in a definite and determinable order. Therefore, any time period can be recognized by its fossil content (correlation)Just like we determined the age of the movie based on the Suns players (fossil content)
28Relative Dating - Fossils Index Fossil - a fossil that is only found in a specific time periodKey Concept 15: Index fossils are widespread geographically, are limited to a short span of geologic time, and occur in large numbers
33Absolute DatingHow do we determine the actual age of certain geological features? Or the earth?Relative dating only goes so far, we need a way to actually date thingsKey Concept 17: Absolute dating uses radioactive decay to give scientists an actual age of rocks and mineralsRadioactive decay: a nucleus of an unstable atom loses energy by emitting particles of ionizing radiation
34Structure of the atomIn order to understand absolute dating and radioactive decay you need to understand the structure of the atomKey Concept 18: An atom consists of subatomic particles called protons, neutrons, and electrons; Protons and neutrons are found in the nucleus and electrons are found outside the nucleus
36Structure of the atom The basics: Protons = positively chargedNeutrons = no charge; neutralElectrons = negatively chargedAtomic number = number of protons; the identity of the elementAtomic mass = protons + neutrons
37Absolute DatingKey Concept 19: When nuclei are unstable, they spontaneously break apart, or decay, in a process called radioactivityThere are 3 types of radioactive decay:Alpha emissionBeta emissionElectron capture
39Absolute DatingKey Concept 20: A half-life is the amount of time necessary for one half of the nuclei in a sample to decay to its stable isotopeKey Concept 21: Each radioactive isotope has been decaying at a constant rate since the formation of the rocks in which it occursThis is how scientists can determine how old rocks areThis is how the age of the earth was determined
40Absolute DatingThere are 2 main radioactive isotopes that are used in absolute dating:Carbon-14 (electron emission)Uranium-238
42Absolute DatingKey Concept 22: An accurate radiometric date can be obtained only if the mineral remained in a closed system during the entire period since its formationKey Concept 23: When an organism dies, the amount of carbon-14 gradually decreases as it decays. By comparing the ratio of carbon-14 to carbon-12 in a sample, radio-carbon dates can be determined