Absolute Age of Rocks Notes

Absolute Dating exact age properties atoms exact When you find the ______ ____ of a rock. Process uses the __________ of ______ in rocks to find their ______ ages. exact age properties atoms exact

three particles neutrons same element same protons different neutrons Atoms have _____ kinds of ________: protons, _________ and electrons Atoms of the ______ ________ have the ______ number of ________, but can have a ________ number of _________ particles neutrons same element same protons different neutrons

6 7 8 element neutrons different Isotope: atoms of an ________ that have ________ numbers of _________ Ex: These are some isotopes of carbon Carbon-12 has __ neutrons Carbon-13 has __ neutrons Carbon-14 has __ neutrons different neutrons 6 7 8 Carbon-12 stable Carbon-13 stable Carbon-14 unstable

unstable isotope breaks down new elements Radioactive Isotope: an _________ isotope Radioactive Decay: when a radioactive ________ (parent isotope) _______ ______ into ____ isotopes (daughter isotope) of different _________. unstable isotope breaks down new elements radioactive isotope new isotope

radioactive isotope new Parent isotope: another name for the ___________ isotope Daughter isotope: ____ ________ formed when the parent isotope breaks down radioactive new isotope parent isotope daughter isotope

Radiometric Dating exact ratio parent daughter radiometric only The process of determining the ______ age of a rock sample based on the _____ of _______ isotope to _________ isotope is called ___________ dating. Can _____ give _________ ages for rocks that have _____ been melted or __________ exact ratio parent daughter radiometric only accurate NOT weathered

calculate age rock amount parent amount daughter half-life parent To _________ the ____ of a _____ you need to know: 1. The ________ of _______ isotope in the rock 2. The ________ of _________ isotope in the rock 3. The ________ of the _______ isotope calculate age rock amount parent amount daughter half-life parent

% of parent isotope remaining Click here & scroll down for the demo Half-life: amount of _____ it takes for ____ of the original amount of ______ isotope in the rock sample to ______, or change ____ the _________ isotope. time half parent decay into daughter % of parent isotope remaining Click here & scroll down for the demo half-lives

12 6 10,000 parent half parent left When the rock formed it had 12mg of parent isotope (100%). 12 Ex: There are ___mg of _______ isotope in the rock to start and the ____-life of the parent is _______ years. After 10,000 years there would be ___mg of the _______ isotope ____ in the rock (half of the original amount). parent 10,000 years pass (1 half-life) half 10,000 Now there is 6mg (50%) of the parent left and 6mg (50%) of daughter isotope have formed. 6 parent Another 10,000 years pass (2 half-lives) left Now 3mg (25%) of the parent left & 9mg (75%) of the daughter formed.

1.3 two commonly used daughter argon-40 rocks 1 million There are ____ parent isotopes __________ _____ in radiometric dating. 1. Potassium-40: Has a half-life of ___ billion years. Decays into the _________ isotope _________. Used to date ______ older than about ________ years. two commonly used 1.3 daughter argon-40 rocks 1 million

4.5 Decays lead-206 older 10 million 2. Uranium-238: Has a half-life of ___ billion years. ________ into the daughter isotope _________. Used to date rocks _____ than about _________ years. Decays lead-206 older 10 million

Some of the Radioactive Isotopes Used in Radiometric Dating

Radiocarbon Dating Carbon-14 is used to date fossils, ______, and wood up to _______ years old. bones 75,000

used organisms bodies carbon constant Carbon from the environment is _____ by ___________ to build tissue in their _______. Throughout their lives, the amount of _______ remains _________. used organisms bodies carbon constant

carbon-14 decays remaining measured age After the organism dies, __________ slowly _______. The __________ carbon-14 can be __________ to determine the ____ of the fossil. carbon-14 decays remaining measured age

How Old is the Earth? age estimated meteorites rocks moon The ____ of the earth is __________ by finding the absolute ages of ___________ from our solar system and ______ from the ______. age estimated meteorites rocks moon

Based on this information, the ____ of the ______ is estimated to be around 4.6 ______ years old age earth billion

Can’t rocks recycled history ______ use rocks on the earth to find the earth’s exact age because the ______ have been _________ or changed over the course of earth’s _______. (the rock cycle) Can’t rocks recycled history