A craton is a large, stable portion of Earth's lithosphere that makes up part of a continent. The Kaapvaal craton in Africa is one of five ancient cratons left from the Precambrian era. The rock has remained tectonically stable since its formation 3.6 billion to 2 billion years ago. What do you think the term "tectonically stable" means? Why do you think this rock formation is important to understanding the history of Earth? Do you think studying ancient rock formations such as the Kaapvaal craton can teach scientists not only about Earth's past but also its future? Why or why not?