Argon is produced in Earth's crust via?

Question

Argon is produced in Earth's crust via?

1. A. Decay of K-40 (Correct answer)
2. B. Volcanoes
3. C. Photosynthesis
4. D. Cosmic rays

Correct Answer

Option A — Decay of K-40

Detailed Solution & Explanation

The correct answer is Decay of K-40.

Key Points

• The argon in Earth's crust — chiefly argon-40 — is produced by the radioactive decay of potassium-40 (K-40) through electron capture and beta-plus decay.
• This is precisely the process behind K–Ar radiometric dating.
• Volcanoes only release already-formed argon, and photosynthesis and cosmic rays are unrelated to argon production. Tie Ar-40 to K-40 decay.