Life after 1 half-life = 1.3 billion years So, With 2 half-lives, it would be: 1.3 * 2 = 2.6 billion years
In short, The Rock is 2.6 billion Years Old
For second question, "<span>sea floor spreading and plate tectonics indicate that the continents do move or shift" and it is the basic principle of Continental drift theory. </span> Hope this helps!