Question

Which dating method is used to date samples from 5,000 years upto 3 billion years old?

• A. Carbon-14
• B. Potassium-Argon (K-Ar)
• C. Uranium Series
• D. Thermoluminescence dating

Hint:

Associate dating methods with their time scales and materials. Carbon-14 is for recent organic remains. TL is for burnt materials (pottery). K-Ar is for very old volcanic rocks, which is crucial for dating fossils found within those rock layers.

Answer 1

The Correct Option is B

Step 1: Concept Overview:
The problem requires identifying a radiometric dating technique effective across a broad range, spanning from thousands to billions of years. Each method's range depends on the half-life of the radioisotope used.
Step 2: Detailed Analysis:
Let's examine the effective dating ranges of each method:
- Carbon-14 (Radiocarbon) dating: Used for dating organic matter, Carbon-14 has a half-life of approximately 5,730 years. It's useful for samples up to roughly 50,000 to 60,000 years old, insufficient for dating samples billions of years old.
- Potassium-Argon (K-Ar) dating: Applied to dating volcanic rocks and minerals, this method relies on the decay of Potassium-40 ($^{40}$K) into Argon-40 ($^{40}$Ar). $^{40}$K has a long half-life of about 1.25 billion years, making K-Ar suitable for dating very old geological samples, from thousands to billions of years old. It's frequently used to date early hominin sites in East Africa.
- Uranium Series dating: Encompassing methods like Uranium-lead and Uranium-thorium dating, Uranium-lead is used for dating extremely old samples (billions of years), while Uranium-thorium is used for younger samples (up to 500,000 years). While the Uranium series covers a wide range collectively, Potassium-Argon is a single method widely known for its broad application in paleoanthropology.
- Thermoluminescence (TL) dating: Used to date fired crystalline materials, such as pottery or burnt flint. Its effective range extends from a few hundred years to about 500,000 years. This is not suitable for the upper limit required.
Step 3: Conclusion:
Comparing the options, Potassium-Argon (K-Ar) dating is the single most suitable method spanning the time from thousands to billions of years.