Dating Methods: Uncovering Earth's History

  • Thread starter ArmitageT1
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In summary, Potassium-Argon dating is the basis for the argument between an uncle and a nephew about the age of the Earth. Different radiometric dating methods are used to give ages of millions or billions of years for rocks. The assumption made is that decay rates have always been constant. If any of these assumptions are not met, the age given is false.
  • #1
ArmitageT1
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Hi all,

I'm new here and have a rather simple question... how are objects in the Earth's crust, such as fossils, dated? I understand that 40,000-65,000 years is the average availability of years that certain organic materials can be dated with carbon-14 dating, so how are numbers of years such as the arrival of the dinosaurs 250 million years ago discovered?

This is a topic my uncle and I frequently argue on. He's a fundamentalist Christian and states the Earth is around 10,000 years old (something I get nearly furious with every time we discuss the issue) and of course this statement isn't based on science, but I wouldn't know how to respond if he asked me HOW we know that dinosaurs first walked the Earth 250 million years ago.

I apologize if this is an extremely mundane topic for most of you (I imagine it is) and that if it gets in the way of many more complex issues.

Thanks,
C.J.
 
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  • #2
Welcome, C.J. Don't worry about asking. We have to start somewhere of course, anyway I think you might want to read this paper very carefully

http://www.asa3.org/aSA/resources/Wiens.html
 
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  • #3
Thanks

Andre said:
Welcome, C.J. Don't worry about asking. We have to start somewhere of course, anyway I think you might want to read this paper very carefully

http://www.asa3.org/aSA/resources/Wiens.html

Thank you very much for the link. This explains a lot.
 
  • #4
ArmitageT1 said:
Hi all,

I'm new here and have a rather simple question... how are objects in the Earth's crust, such as fossils, dated? I understand that 40,000-65,000 years is the average availability of years that certain organic materials can be dated with carbon-14 dating, so how are numbers of years such as the arrival of the dinosaurs 250 million years ago discovered?

This is a topic my uncle and I frequently argue on. He's a fundamentalist Christian and states the Earth is around 10,000 years old (something I get nearly furious with every time we discuss the issue) and of course this statement isn't based on science, but I wouldn't know how to respond if he asked me HOW we know that dinosaurs first walked the Earth 250 million years ago.

I apologize if this is an extremely mundane topic for most of you (I imagine it is) and that if it gets in the way of many more complex issues.

Thanks,
C.J.
The answer is simple, Potassium-Argon Dating
http://en.wikipedia.org/wiki/Potassium_argon_dating
 
  • #5
The following quoted text is from this article: http://www.answersingenesis.org/docs2002/carbon_dating.asp" [Broken]

This is the basis for your Uncle's argument.

There are various other radiometric dating methods used today to give ages of millions or billions of years for rocks. These techniques, unlike carbon dating, mostly use the relative concentrations of parent and daughter products in radioactive decay chains. For example, potassium-40 decays to argon-40; uranium-238 decays to lead-206 via other elements like radium; uranium-235 decays to lead-207; rubidium-87 decays to strontium-87; etc. These techniques are applied to igneous rocks, and are normally seen as giving the time since solidification.

The isotope concentrations can be measured very accurately, but isotope concentrations are not dates. To derive ages from such measurements, unprovable assumptions have to be made such as:

1. The starting conditions are known (for example, that there was no daughter isotope present at the start, or that we know how much was there).

2. Decay rates have always been constant.

3. Systems were closed or isolated so that no parent or daughter isotopes were lost or added.
 
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  • #7
Weell obviously isotope ratios are the answer. But it's interesting to note that some christian scientists propose that god (or some other mighty force) sped up the decay rates to give the illusion that these things are older.

Clutching at straws if you ask me, but it's something your uncle might say.
 
  • #8
Please change the thread title, it's false advertisment! Thanks.
 

What is radiometric dating?

Radiometric dating is a dating method that uses the decay of radioactive elements to determine the absolute age of rocks and other geological materials. This method is based on the principle that certain elements, such as uranium and potassium, undergo radioactive decay at a constant rate over time.

How does radiocarbon dating work?

Radiocarbon dating, also known as carbon dating, is a dating method that uses the decay of carbon-14 to determine the age of organic materials. Carbon-14 is a radioactive isotope that is constantly formed in the Earth's atmosphere and is absorbed by living organisms. When an organism dies, it stops absorbing carbon-14 and the amount of carbon-14 in its remains gradually decreases over time, allowing scientists to determine its age.

What is the difference between relative and absolute dating?

Relative dating is a dating method that determines the age of a rock or fossil by comparing its position in the rock layers to other nearby rocks or fossils. It can provide an estimate of the age of the object, but not an exact age. Absolute dating, on the other hand, uses scientific techniques to determine the precise age of an object, such as radiometric dating or dendrochronology.

What is the principle of superposition?

The principle of superposition is a fundamental concept in geology that states that in a sequence of undisturbed rock layers, the oldest rocks are at the bottom and the youngest rocks are at the top. This principle is used in relative dating to determine the relative ages of different rock layers.

How do scientists use tree rings to date objects?

Dendrochronology, or tree-ring dating, is a dating method that uses the patterns of tree rings to determine the age of wooden objects or ancient trees. Trees grow a new ring every year, and the width and characteristics of these rings can be used to date the tree's age and the climate conditions during that year. By comparing the rings of different trees, scientists can create a timeline of past events and match the rings of an unknown tree to this timeline to determine its age.

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