Many volcanoes occur at spreading centers where tectonic plates move apart from each other, or subduction zones where two plates collide and one is pushed deep beneath the other. This helps explorers hone in on a region where they are likely to find underwater volcanic activity. From there, explorers utilize seafloor mapping tools such as multibeam sonar. This tool creates high-resolution images by using multiple, simultaneous sonar beams (sound waves) at once in a fan-like pattern or “swath.” Multibeam sonar also measure the depth of the seafloor, which allows the mapping team to create two-dimensional or three-dimensional maps of the seafloor. Backscatter data from the sonar technologies can also reveal plumes of bubbles or hydrothermal vent activity which are signs of an active volcanic area. Following a mapping survey, the expedition team plans a Remotely Operated Vehicle (ROV) dive to further explore the underwater volcano.