Volcanoes are a part of the earth, and they have intrigued people for hundreds of years. Scientists study the earth's plates in order to understand the complexity of volcanic activity around the world. They also study different types of lava, rocks, and the gases that have dissolved into rocks. In the past, studying volcanic activity was extremely dangerous for scientists. Now they have access to tools, such as global positioning systems and seismometers, to help in predicting volcanic activity.