Clocks in the Rocks

August 29th 2008Kimberly Samson

ENG 5300

Earth Systems Science

http://images.google.com/imgres?imgurl=http://etudesproject.org/sofia/gallery/geography/images/at-hyd-lith.gif&imgrefurl=http://etudesproject.org/sofia/gallery/geography/lessons/lesson01.html&h=235&w=243&sz=11&hl=en&start=12&um=1&tbnid=9dzH89O1AdfhTM:&tbnh=106&tbnw=110&prev=/images%3Fq%3Dearth%2Bscience%2Bsystems%2Bvenn%2Bdiagram%26um%3D1%26hl%3Den%26rlz%3D1T4BBYA_en___US251%26sa%3DN

How Old Are Rocks?Relative Age

Relative Age can be determined by the Principle of Superposition -assuming no change in the layers, the oldest are on the bottom and the youngest are on the top.

How Old Are Rocks?Absolute Age

Radioactive dating can determine the Absolute Age of rocks.

Isotopes

Isotopes are elements that differ in number of neutrons.

Some isotopes decay emitting energy Radioactive Rate at which elements decay

determines rocks absolute age Radioactive isotopes include:

Potassium, rubidium, strontium, uranium, and lead.

Radioactivity

Unstable nuclei emits one or more particles or energy in the form of electromagnetic radiation

Nuclear radiation is the energy or matter released during the decay

Types of Nuclear Radiation

Alpha +2 chargeα

Beta -1 chargeβ

Gamma 0 charge γ

What happens to the Atomic Number?

Alpha-Atomic # goes down by 2-Mass goes down by 4;can penetrate a piece of paper

Uranium-238 decays through a decay into Thorium-234

Beta-Atomic # goes up by 1-Mass has no change; can penetrate a piece of aluminum

Gamma-Atomic # and mass have no change; very powerful light energy; can penetrate lead

238 92

U ______________ 23490 Th

23490 Th ______ 234

91 Pa ______ 23492 U

Neutron Emission

Release of high-energy neutron by a neutron-rich nuclei during radioactive decay

No Charge Travel farther than alpha and beta

particles

Radioactive Decay Rates-Half Life

Half-life is the time required for half a sample of radioactive nuclei to decay

Half-life rates of common isotopes:Carbon-14 5,730 yearsThorium-229 7,340 yearsLead-202 52,500 yearsUranium-238 4,468,000,000 yearsRubidium-87 4,750,000,000 years

Radiometric Dating-Clocks in the Rocks

Virtual Dating Science Courseware viewed on July 19th 2008

Radiometric Dating Cont.

Radiometric Dating Berkley on July 19th 2008

Half-Life Activity

http://turbulentdensity.com/uploaded_images/pennies-721745.jpg

http://images.google.com/imgres?imgurl=http://www.sfondideldesktop.com/Images-Games/Half-Life-2/Half-Life-2.jpg&imgrefurl=http://www.freewebs.com/metroid003/photolab.htm&h=768&w=1024&sz=198&hl=en&start=7&um=1&tbnid=TbQwGeWJPBClNM:&tbnh=113&tbnw=150&prev=/images%3Fq%3Dhalf%2Blife%26um%3D1%26hl%3Den%26rlz%3D1T4BBYA_en___US251%26sa%3DN

Nuclear Strong Force

Nuclear Strong Force-interaction that binds protons and neutrons together in a nucleus

Contributes to stable nuclei Too many neutrons or

protons cause nucleus to become unstable

http://www.atomki.hu/atomki/NuclSpect/nucleus.jpg

Nuclear Fission Nuclear Fission-process when a nucleus

SPLITS into two or more smaller fragments

Energy is released Neutrons released can start a chain

reaction Chain reactions can be controlled

http://ozymandias1.files.wordpress.com/2008/05/chain-reaction.jpg on August 21st 2008

Nuclear Fusion Nuclear Fusion-process when light

nuclei combine at extremely high temperatures, forming heavier nuclei and releasing energy

http://images.google.com/imgres?imgurl=http://news.bbc.co.uk/nol/shared/spl/hi/pop_ups/05/sci_nat_iter___the_next_generation_fusion_reactor/img/2.jpg&imgrefurl=http://news.bbc.co.uk/2/shared/spl/hi/pop_ups/05/sci_nat_iter___the_next_generation_fusion_reactor/html/2.stm&h=300&w=300&sz=14&hl=en&start=9&um=1&usg=__pJbSvkXpHCoit9iMZ47jR9UXpYc=&tbnid=snU7uPDsocrZ6M:&tbnh=116&tbnw=116&prev=/images%3Fq%3Dsun%2Bfusion%26um%3D1%26hl%3Den%26rlz%3D1T4BBYA_en___US251%26sa%3DN

http://www.atomicarchive.com/Fusion/Images/fusion.jpg accessed on August 21st 2008

Resources

http://www.idahogeology.org/FieldWorkshops/Island_Park_2007b/Cash_Activities/Half-life_activity.pdf accessed on July 18th 2008

http://richardbowles.tripod.com/chemistry/radio/radio.htm accessed on August 21st 2008

http://nemo.sciencecourseware.org/VirtualDating/ access on July 18th 2008

http://astro.berkeley.edu/~dperley/areopagus/isotopetable.html accessed on August 21st 2008

Dobson, K., Holman, J. and Roberts, M. Holt Science Spectrum : A Physical Approach. (2001) New York: Holt, Rinehardt and Winston.(Chapters 7 and 17)

Note: All websites accessed on July 18th, July 19th or August 21st 2008.