We think you have liked this presentation. If you wish to download it, please recommend it to your friends in any social system. Share buttons are a little bit lower. Thank you!
Presentation is loading. Please wait.
Published byAdolfo Leeder
Modified over 2 years ago
Science and Creationism 5. Radiometric Dating © Colin Frayn,
© Colin Frayn, Background What is radiometric dating? –A method for ascertaining the age of a sample –Uses the known decay rate of different radioactive elements Naturally present in the sample when it was formed Decay over time –Different techniques Using different elements –Applicable across a range of timescales Centuries to billions of years –Based on fundamental physics –Error-correcting
© Colin Frayn, Assumptions Does radio-isotope dating rely on assumptions? –Original quantity needs to be known Not true Isochron dating allows us to determine the original quantity –Decay rate doesnt change Decay rates never change This is fundamental physics –No contamination Again, not actually an assumption We can easily test for contamination
© Colin Frayn, Isochron Dating Measure the parent, daughter, and sister elements –Sister is a different isotope of daughter element –E.g. 87 Rb/ 86 Sr plus 87 Sr Benefits –Initial amount of daughter need not be known We can work it out! –Contamination can be spotted We know if contamination has occurred because the points will not be colinear –Loss/gain of daughter isotope can be spotted Again, we can test for this and avoid calculating dates for unreliable samples Checks –We can test dating methods by using several different tests on the same sample If 3 or 4 independent methods all agree on the same age then the chance that they were all wrong by the same enormous factor seems impossible –We can test some recent dating methods by calibration Check with dates from other sources e.g. volcanic eruptions, the Earths orbital cycles etc. C 14 C 12 N 14 N 15 Decay DaughterSister ParentStable Parent
Isochron Dating Example © Colin Frayn, Parent : Sister Ratio Daughter : Sister Ratio
© Colin Frayn, Examining Isochron Dating Possible problems: –Rock didnt form in one epoch For example, by repeated re-melting Geological samples are usually very obviously cogenetic (formed at the same time) or not Isochron methods would give the youngest age in this case –So the sample could only be older! –Rock is mixed from two sources This can be detected Other tests show that this is a very rare occurrence All possible mishaps either… 1.Have a small effect, at most a few 10s of % 2.Underestimate the true age of the sample
© Colin Frayn, Time ladder Are radiometric dating methods just calibrated from each other? No – they can also be calibrated using many other methods –C-14 dating can be calibrated against known archaeological remains –Dating of the Hawaiian archipelago is consistent with tectonic models –(Dating is consistent with Milankovitch cycles) –Dating is consistent with the luminescence method –Dating is consistent with geological models of deposition
© Colin Frayn, Errors An understanding of exponentials helps… A measurement error of 2 times does not mean a date error of 2 times –It means a date error of 1 half life C-14 dates down to 6,000 years from 40,000 years –Requires an error of roughly a factor of almost 80 in measurement! If a sample is polluted with extra parent isotope –Then ages would be an underestimate! Multiple different, independent dating methods can be applied to one sample –You can check that they agree
© Colin Frayn, Dating Mammoth Remains One part dated 29,500 yrs, another 44,000 yrs? –No, this is a lie The dates refer to two samples in one paper The samples are of different animals! –The paper referenced: USGS Professional Paper 862, Troy Péwé (1975) A similar dishonesty is also used to claim that a Siberian mammoth was dated unreliably –Again, these were samples from different sources
© Colin Frayn, Carbon-14 in Coal Baumgardner, 2003 –Claims that there is C-14 in very old coal deposits From the Carboniferous, 300 Myr ago –Proves that the deposits are young? C-14 can be produced in minute amounts by other processes –Natural decay of Uranium-Thorium isotopes –Possibly also from bacteria/fungi in some circumstances C-14 is only found in some, not all oil/coal deposits Contamination could also be a factor Research is ongoing into this discovery
© Colin Frayn, Anomalous Carbon-14 Keith & Anderson, 1963 –Living mollusc shells were dated as 2300 yrs old –This claim ignores two things: The snails were living in an extreme environment with poor access to atmospheric carbon Dating shells doesnt work! Molluscs get much of their carbon from dissolved limestone (which is old!) Wakefield, 1971 –A recently dead seal was dated as 1300 yrs old –This is due to the (well-known, documented) effect of lower C-14 activity around Antarctica –Old water upwells from the ocean, skewing ages –This only affects (some) ocean-dwelling creatures Riggs, 1984 –Living snails were dated to 27,000 yrs old –Snails were living in artesian springs –Yet another example of how dating shells is dodgy –Has no implications for the validity of the rest of C-14 dating
© Colin Frayn, K-Ar Anomalies This method has been largely replaced by more reliable 40 Ar/ 39 Ar methods Funkhouser and Naughton, 1968 Recent volcanic lava dated to 1.6Myr Not quite true – they dated xenoliths in the lava Examination of the lava showed that the Argon levels were raised So this was a clear that the K-Ar method wouldnt work This is a known flaw with K-Ar dating in some rocks Other methods date these rocks just fine Dalyrmple, 1969 Analysis of historic lava flows using 40 Ar/ 36 Ar More anomalous readings Effect on old rocks is negligible Dalrymple showed that the 40 Ar/ 39 Ar method worked fine
1 Section 8.2 Determining Absolute Age. Objectives Summarize the limitations of using the rates of erosion and deposition to determine the absolute age.
Absolute Age Finding a rocks birthday. Absolute Age? Give an example of an absolute age of a rock layer… That rock layer is 200 million years old. Remember,
Lecture 13: Box Models and Mixing Theory, Origin of Atmosphere and Hydrosphere Questions –How do geochemists interpret compositional data in terms of mixing.
LESSON 10 – Earths History: Estimating Geologic Time Modified from
Sedimentation and the Fossil Story. The evidence supporting evolution comes from many sources. You could think of it as a jigsaw puzzle which produces.
Fossils are usually formed when an organism is covered by sediments that then harden into sandstone, slate, mudstone or flint. Most organisms do not fossilize.
The. of and a to in is you that it he for.
CHAPTER 20 Nuclear Chemistry and Radioactivity 20.3 Rate of Radioactive Decay.
What pieces of evidence do scientists use to back up the theory of Evolution? What pieces of evidence do scientists use to back up the theory of Evolution?
Geological Time - really, really, really long! Motion pictures are generally projected at 32 frames per second. Therefore, each frame (image) is on the.
1 Evidence For a Young World Dr. Heinz Lycklama What I see convinces me God exists. What I cannot see, confirms it. Albert.
1 Lecture 19: Noble Gas Geochemistry Questions –What are the isotopic and elemental distributions of the noble gases He, Ne, Ar, Kr, Xe, and Rn in the.
P1 - The Earth in the Universe. Big Bang 14 thousand million years ago Theory was proposed by the Catholic Priest George Lemaitre.
The Rock Record Chapter 8. Preview the chapter pages Look at headings Look at pictures Read the yellow highlighted words.
The Greenhouse Effect on Earth Earths atmosphere is slightly warmer than what it should be due to direct solar heating because of a mild case of greenhouse.
1 Lecture 18: Chemical Geodynamics, or Mantle Blobology Questions –What can geochemistry tell us about the deep interior of the Earth? –Is the mantle homogeneous.
APOLOGETICS Session 5 – Science of Creation 1 Creation (what the Bible says) 1. Theophanies and who created the world? 2. How old is the world/life? 1.
The Rock and Fossil Record Chapter 6 Earths Story and Those Who First Listened Relative Dating: Which Came First? Absolute Dating: A Measure of Time Looking.
Geologic Time and Earth History Dr. R. B. Schultz.
How do we collect the data?. Who collects the data? IPCC – Intergovernmental Panel on Climate Change NASA Universities Meteorological Centres Environmental.
Geologic Time (History as told by Rocks). The Rock Record Geological Time Scale Dividing the Earth’s history into sections based on the fossils and.
1 Lecture 12: Radioactivity Questions –How and why do nuclei decay? –How do we use nuclear decay to tell time? –What is the evidence for presence of now.
Term Test 2 Click Here. This presentation is completely interactive In order for this presentation to work you MUST follow the indicated tabs on each.
1 Costing 2 Accounting Prof. Clive Vlieland-Boddy Academic Year
The meaning of Reliability and Validity in psychological research.
SAMPLE EXERCISE 21.1 Predicting the Product of a Nuclear Reaction What product is formed when radium-226 undergoes alpha decay? Solution Analyze: We are.
SADC Course in Statistics Putting the Life Table in Context (Session 15)
Geologic Time 1. Which geologic event took place first and when? when? Which rock layer is older, and how is earth Which rock layer is older, and how.
Intro to Evolution Evolution simply means change over time. many things evolve, including languages, and your view of the world.
By Tabitha Odutayo What is carbon footprint How we calculated our carbon footprint Finding out your carbon footprint Comparison Why carbon footprints.
© 2016 SlidePlayer.com Inc. All rights reserved.