When geologists tried to test how old the volcanic rock was on Reunion Island in the Indian Ocean their results varied from 100 000 years to 4.4 billion years. Different radioactive methods gave contradictory results. Potassium/Argon gave the youngest, Uranium/Lead gave the oldest results.
Based on data obtained from Geochimica et Cosmochimica Acta, vol.35, 1971, pp.261-288 and vol.36, 1972, p.1167.