absolute time
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Absolute Time. Mrs. Wright 8 th Grade Science Bath County Middle School. Absolute Ages of Rocks. Absolute age is the age, in years, of a rock or other object. Geologists determine absolute ages by using properties of the atoms that make up materials. Radioactive Decay. - PowerPoint PPT PresentationTRANSCRIPT
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Absolute TimeAbsolute Time
Mrs. WrightMrs. Wright
88thth Grade Science Grade Science
Bath County Middle SchoolBath County Middle School
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• Absolute age is the age, in years, of a rock or other object.
• Geologists determine absolute ages by using properties of the atoms that make up materials.
Absolute Ages of Rocks Absolute Ages of Rocks
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Radioactive Decay
• Some isotopes are unstable and break down into other isotopes and particles.
• Sometimes a lot of energy is given off during this process.
• The process of breaking down is called radioactive decay.
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Half-Life
• The half-life of an isotope is the time it takes for half of the atoms in the isotope to decay.
• After two half-lives, one fourth of the original isotope still remain.
• After three half-lives, one eighth of the original isotope still remain.
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Radiometric Ages
• As time passes, the amount of parent isotope in a rock decreases as the amount of daughter product increases.
• By measuring the ratio of parent isotope to daughter product in a mineral and by knowing the half-life of the parent, in many cases you can calculate the absolute age of a rock. This process is called radiometric dating.
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Radiometric Ages
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Uniformitarianism
• Before the discovery of radiometric dating, many people estimated that Earth is only a few thousand years old.
• But in the 1700’s, Scottish scientist James Hutton estimated that Earth is much older.
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• He used the principle of uniformitariansm. This principle states that Earth processes occurring today are similar to those that occurred in the past.
Uniformitarianism
• Hutton’s principle is often paraphrased as “the present is the key to the past.”
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Uniformitarianism• Today, scientists
recognize that Earth has been shaped by two types of change: slow, everyday processes that takes place over millions of years, and violent, unusual events such as the collision of a comet or asteroid about 65 million years ago that might have caused the extinction of the dinosaurs.
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Question 1
__________ age is the age in years of an object.
A. AbsoluteB. CalculatedC. DerivedD. Relative
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Answer
The answer is A. Geologists use properties of atoms in specific materials to determine absolute age.
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Question 2
What is meant by the term “half-life” of an isotope?
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Answer
The half-life of an isotope is the time it takes for half of the atoms in the isotope to decay.
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Question 3
What information must you have in order to conduct radiometric dating?
Answer
You must have an isotope with an appropriately short or long half-life. You must also know the isotope’s half-life and be able to measure the ratio of parent isotope to daughter product.