The Pacific Rim is an area that encompasses those land masses surrounding and within the Pacific Ocean. The Pacific Rim as a region is significant due to its high levels of volcanism and tectonic activity. The boundaries are often referred to as the “Ring of Fire” because it is home to the world’s foremost belt of volcanic activity, comprising over 75% of the world’s active and dormant volcanoes. The Ring of Fire arc stretches from New Zealand to the eastern edge of Asia and then north across the Aleutian Islands of Alaska and south along the coasts of North and South America. The Ring of Fire is situated at the juncture of the Pacific and the Antarctic, Nazca, Cocos, North American, Eurasian, and Indo-Australian tectonic plates.
As the Pacific Plate moves northwestward, colliding with and sliding underneath other plates (known as subduction), rock is melted into magma and rises to the surface as lava, forming volcanoes over “hot spots.” Island chains are a result of the plate passing over these hot spots leading to volcanic eruptions. Linear island archipelagoes such as Hawaii are characterized by volcanism, earthquakes, and deep ocean trenches surrounding the islands.
All of Earth’s tectonic plates are in flux; when they move, intense geologic activity occurs along the edges. Several things can happen as a result. For example, when the plates move away from each other, magma from the earth’s core will rise up to form a new seafloor and may eventually break through the ocean’s surface to form an island. Alternately, when the plates move toward each other, they will either slide past each other, or subduction will occur.
If parts of a plate boundary slide past one another in opposite directions (for example, the San Andreas
Fault), minor earthquakes can occur. The faults also may create cliffs thousands of feet high on the ocean bed. When two plates collide and one is forced under the other, deep into the Earth’s interior, the subsumed plate encounters high temperatures and pressures that partially melt solid rock. Some of this newly formed magma rises to the Earth’s surface and erupts, forming chains of violent volcanoes like the Ring of Fire. These narrow plate-boundary sites, known as subduction zones, are also associated with the formation of deep ocean trenches and big earthquakes. When there is an earthquake under the sea, one side of the ocean floor suddenly drops downward, beneath the top edge of the subducting plate. The resulting vertical fault will generate a tsunami with often devastating consequences.
The movement of the Indo-Pacific Plate under the Pacific Plate has created volcanoes in New Guinea and Micronesia. The resulting volcanism has created a myriad of different island types. High volcanic islands such as the island volcano of Krakatau (“Krakatoa”) in Indonesia, which erupted on August 26, 1883, created a series of huge tsunamis, some of which reached heights of 40 meters and killed more than 36,000 people on the islands of Java and Sumatra.
The Ring of Fire—and hence the Pacific Rim—are important not only because of the natural catastrophes which can result, but for the impact they have had—and still have—on human populations. The formation of new land masses in the ocean greatly influenced the movement of prehistoric peoples across the seas, led to the development of hundreds of unique cultures in partially or totally isolated environments, and helped us to understand how people adapted to insular environments.
- Irwin, G. (1992). The prehistoric exploration and colonisation of the Pacific. Cambridge: Cambridge University Press.
- Kirch, P. V. (2000). On the road of the winds: An archaeological history of the Pacific Islands before European contact. Berkeley, CA: University of California Press.
- Page, B. M., Ernst, W. G., & Coleman, R. G.(Eds.). (2000). Tectonic studies of Asia and the Pacific Rim: A tribute to Benjamin M. Page (pp. 1911-1997). International Book Series, 3. Geological Society of America.