Question

Potassium-40 can be used to date ________ that are ________ old.

A. volcanic rocks and associated fossils; hundreds of millions of years
B. carbon-containing materials; up to 75,000 years
C. fossils; thousands of years
D. potassium-rich fossils; millions of years

Answer 1

Potassium-40 is used for radiometric dating of volcanic rocks and associated fossils that are hundreds of millions of years old, owing to its long half-life of 1.25 billion years. Option A.

Step-by-step explanation:

Potassium-40 (K-40) is a radioactive isotope that is used in radiometric dating to determine the age of rocks and minerals. When K-40 decays, it turns into Argon-40 (Ar-40). K-40 has a half-life of 1.25 billion years, making it suitable for dating materials that are millions to billions of years old.

Specifically, Potassium-40 can be used to date volcanic rocks and associated fossils that are hundreds of millions of years old. The process involves measuring the ratio of Ar-40 to K-40 in a rock sample, and this ratio indicates how long it has been since the rock solidified and trapped the Ar-40 produced by the decay of K-40. Option A.