Radiometric dating estimates rock ages based on the decay of radioactive elements (parent components) into stable elements (daughter components). The most frequently cited long-age radioactive decay clocks are Uranium-Lead, Potassium-Argon, and Rubidium-Strontium, but there are over 40 such methods.
These methods are used for igneous rocks formed when hot molten material cools and solidifies (like granite, basalt). They aren’t used on sedimentary rocks formed from water-deposited particles (like limestone, shale, sandstone).
The clock starts when the rock has solidified. It’s thought that while molten the extreme heat would cause gaseous daughter elements like argon and low melting-point elements like lead to escape. Once cool it’s assumed that no more daughter element can escape, so any found is deemed the result of radioactive decay of the parent in the igneous rock.
The decay rate is measured in terms of half-life. That’s the length of time it takes for half of the parent element to decompose into the daughter element.
Estimated half-lives for the most commonly used methods are:
Uranium 238 – Lead 206 (U-Pb, Half-life = 4.5 billion years),
Potassium 40 – Argon 40 (K-Ar, Half-life = 1.3 billion years), and
Rubidium 87 – Strontium 87 (Rb-Sr, Half-life = 47? 60? 120? billion years).
Both of the latter two methods are calibrated with the first.
A more technically complicated method called isochron dating purports to avoid assumptions about initial daughter concentrations by using ratios. However, it involves other assumptions and gives invalid values if the assumptions are wrong.
Soli Deo Gloria.
This is the 33rd in a series of blog posts on the Age of the Earth. I began with the Biblical testimony that the earth is 6,000 years old, because the evidence from nature should be interpreted and understood in the light of clear Biblical truth. The prequels have considered the issue’s importance, what Jesus thought, the Genesis genealogies, and the historic teaching of the church. Current articles are discussing scientific evidence on the age of the earth, explaining fallacies of radiometric dating methods and giving examples of scientific methods which yield short ages.
Read the prequels:
1. How Old Is the Earth?
2. Why Is the Age of the Earth Important?
3. Earth: Young or Old?
4. Age of the Earth—Jesus’ View
5. Age of the Earth—Jesus Interpreted OT Literally
6. Age of the Earth—What Did Jesus Say?
7. Age of the Earth—What Did Jesus’ Contemporaries Think?
8. Age of the Earth—Genealogies
9. Age of the Earth—What Does Begat Mean?
10. Age of the Earth—Interlocking Genealogies
11. Age of the Earth—Any Gaps in Genealogies?
12. Age of the Earth—No Gaps in Genealogies
13. Age of the Earth—Any Missing Generations?
14. Age of the Earth—Scriptural Confirmation (Adam to Noah)
15. Age of the Earth—Scriptural Confirmation (Noah to Abraham)
16. Age of the Earth—Luke’s Testimony
17. Age of the Earth—Luke & Cainan Puzzle
18. Age of the Earth—Luke & Cainan Explanation
19. Age of the Earth—Add It Up
20. Age of the Earth—6,000 Years Old
21. Age of the Earth—History’s View
22. Age of the Earth—Church Fathers’ Opinion
23. Age of the Earth—Josephus, Luther, Calvin
24. Age of the Earth—Archbishop Ussher
25. Age of the Earth—Prof. James Strong
26. Age of the Earth—Kepler & Newton
27. Age of the Earth—Dr. William Hales
28. Age of the Earth—Prof. Leupold
29. Age of the Earth—Prof. Barr
30. Age of the Earth—History’s Opinion
31. Age of the Earth—Radiometric Dating
32. Age of the Earth—Scientific Clocks
Read the sequel:
34. Age of the Earth—Radiometric Dating Fallacies
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©William T. Pelletier, Ph.D.
“contending earnestly for the faith”
“destroying speculations against the knowledge of God”
“for the defense of the gospel”
(Jude 1:3; 2 Cor 10:5; Phil 1:16)
Tuesday October 7, 2008 A.D.
For in six days the LORD made the heavens and the earth, the sea and all that is in them, and rested on the seventh day; therefore the LORD blessed the Sabbath day and made it holy. (Exodus 20:11 NASB)