The Pacific Ring of Fire covers a significant amount of area on its boundaries, so there's plenty of space for people to live along it. In addition, the nearby land is coastal, and coastal areas are popular for settlements.
According to the United Nation's Atlas of Oceans, approximately 44 percent of the world's population lives in coastal regions. The Pacific Ring of Fire has coastline along Asia, all of western North and South America and in Oceania. This sheer volume of coastal land, combined with the long history of people in Asia, means that many settlements have sprung up bordering the Ring of Fire.
Most of the area within the Ring of Fire rests on the Pacific tectonic plate, and the coastal areas around it have a series of plates that bump into it. The friction created as these plates move causes the earthquakes and volcanic activity throughout the region.
The Ring of Fire contains 75 percent of the world's active and dormant volcanoes. Ninety percent of the world's earthquakes occur along its tectonic boundaries. It also contains several of the world's largest metropolitan areas, including Tokyo, Japan, which has the largest metropolitan population; Seoul, South Korea, which has the world's second largest metropolitan population; and Los Angeles, which is the second most populous region of the United States.