You probably already know a lot about geologic time and the Earth's past from your own general knowledge. You may have picked up this background from your own reading, from TV, from movies, or from other areas. Below you will find a series of statements concerning geologic time and the Earth's past. Not all of them of them are true. All of the concepts in the statements will be fully explored in the lessons, but before you review the lessons, let's see what you already know about geologic time and the Earth's past. Carefully think about each statement. Then decide, to the best of your knowledge, whether you agree or disagree with each statement. At the end of the unit, you'll be able to review these statements again to see how much you have learned.

1. The Earth is approximately 4.6 billion years old. (Agree / Disagree)
   
   
2. The underlying principle of all of geology is the belief that geologic forces at work on the Earth today were also at work in the past. (Agree / Disagree)
   
   
3. In a sequence of sedimentary rocks, the lowest sedimentary layer is always the oldest layer. (Agree / Disagree)
   
   
4. Radioactive decay is a widely used method for determining the ages of rocks. (Agree / Disagree)
   
   
5. The first supercontinent was known as Pangaea. (Agree / Disagree)
   
   
6. Dinosaurs flourished in the time period known as the Paleozoic Era. (Agree / Disagree)
   
   
7. The death of the dinosaurs represents the largest mass extinction that the Earth has ever known. (Agree / Disagree)
   
   
8. The world's largest known volcanic eruptions occurred 251 million years ago in Siberia, Russia. (Agree / Disagree)