Introduction: Mount St. Helens erupted on May 18, 1980. It became the most catastrophic volcanic eruption in United States history. On June 15, 1991, Mount Pinatubo erupted in the Philippines. Its eruption would become the second largest volcanic event of the 20th century. Although these two volcanoes erupted over a decade apart and an ocean away, they share a common bond. Both volcanoes are part of the Ring of Fire. 

The Ring of Fire is the region surrounding the Pacific Ocean known for its large number of volcanoes and earthquakes. It is also called the Circum-Pacific belt.

The Ring of Fire is home to over 450 volcanoes and about 90% of all earthquakes. Geographically, it follows the rim of the Pacific Ocean. Its path includes the west coasts of South America and North America. It curves across the northern Pacific by the Aleutian Islands. Then, it continues down along Japan and New Zealand. In all, the Ring of Fire covers over 25,000 miles (40,000 kilometers).

The Ring of Fire owes its volcanoes and earthquakes to it active tectonic plate margins. It follows the boundaries of several tectonic plates, the largest of which is the Pacific Plate. The Ring of Fire also boarders several smaller plates including the Juan de Fuca, Cocos, Nazca, and Philippine plates. The high rate of tectonic activity is largely due to the number of subduction zones around the Ring of Fire. A subduction zone is a type of convergent plate boundary. It forms when a dense tectonic plate moves under a less dense plate. Often this occurs when oceanic crust slides under continental crust. This process creates magma, the key ingredient for volcano formation. The pressure created as the plates move together results in increased earthquake activity.

Directions for This Lesson: Try the practice questions to see what you know about the Ring of Fire. Then, further explore the Ring of Fire by trying the activity.

 

Use an interactive map to visualize volcanic and earthquake activity around the Ring of Fire.

 

Practice what you have learned by completing the post-lesson worksheets.