The eruption of Etna
A stream of lava at the time of the eruption of Etna. Ancient lava flows are dated using the Potassium- Argon method. As soon as the magma becomes solid, the potassium -40 is trapped. Following this, it slowly transforms due to the radioactivity of the argon atoms that equally stay trapped in the rock. The age of this is then given by the proportion found of both elements.