The natural phenomenon responsible for the Pacific Ring of Fire is primarily tectonic plate movements. This region is characterized by a high level of seismic activity, including earthquakes and volcanic eruptions. The Ring of Fire encircles the Pacific Ocean and is home to around 75% of the world's volcanoes, including famous ones like Mount St. Helens and Mount Fuji. Understanding this phenomenon is crucial for assessing geological hazards and studying the Earth's geological processes.