Radiometric dating
Christopher Columbus reported seeing "a great fire in the Orotava Valley" as he sailed past Tenerife on his voyage to discover the New World in 1492. This was interpreted as indicating that he had witnessed an eruption there. Radiometric dating of possible lavas indicates that in 1492 no eruption occurred in the Orotava Valley, but one did occur from the Boca Cangrejo vent.