ASBOG Practice Exam

Which of the following types of geological formations could Potassium-argon dating be applied to?

1. Volcanic rocks

2. Coal deposits

3. Marine sediments

4. Sandstone layers

The correct answer is: Volcanic rocks

Potassium-argon dating is primarily applicable to rocks that have come from volcanic activity, such as volcanic rocks. This dating technique relies on the radioactive decay of potassium-40 into argon-40, which is a gas. When volcanic rocks solidify from molten material, any argon present escapes. As the rock cools and solidifies, potassium is incorporated into the mineral structure, while argon accumulates over time as potassium-40 decays. This process allows scientists to date the time since the rock was formed or last heated. In contrast, coal deposits, marine sediments, and sandstone layers may not produce reliable dates when using potassium-argon isotopes. Coal is primarily composed of organic material, which does not contain significant amounts of potassium. Marine sediments and sandstones are typically formed from particles of previously existing rocks and minerals and do not have the necessary potassium content or the geochronological history suitable for this method. Thus, volcanic rocks stand out as the optimal subject for potassium-argon dating, making it the correct answer.