Geology And Geophysics

What is the Geological Significance of the Pacific Rim

Cynthia Astle's image for:
"What is the Geological Significance of the Pacific Rim"
Image by: 

For a supposedly "peaceful" ocean, the Pacific Rim harbors some of the world's busiest geological features, including volcanoes and earthquakes. Also known as the "Ring of Fire," the geological features of this region around the Pacific Ocean give scientists insights into the seething cauldron that is the planet's interior.

According to, the region known as the Pacific Rim encompasses the countries bordering the Pacific Ocean. Four-fifths of the world's seismic activity happens in this location. The U.S. Geological Survey, a federal agency, offers some of the most extensive surveys, research papers and maps of Pacific Rim events, including such geological features as plate tectonics, sea-floor spreading, subduction zones and "hot spots."

Plate tectonics could be considered the guiding theory of Pacific Rim geology today. According to this premise, the continents of Planet Earth are actually slabs or plates of rock that "float" on a molten core called magma. The continental plates, which go down about 50 miles deep, bump against each other or grind past one another, such as along the famous San Andreas Fault in California. In one of the more dangerous forms of plate tectonics, one continental plate will slide under another in an action known as "subduction." Subduction zones occur beneath the oceans, such as the Juan de Fuca Plate that plunges beneath the North American Plate in the Pacific Northwest.

Scientists now surmise that continental plates move past one another at rates equivalent to the growth of a human fingernail. However, when the pressure of this movement deep inside the Earth builds up sufficiently, the force causes brittle surface plates to break suddenly, resulting in earthquakes. This natural event can be mildly disturbing or it can be devastating to human, animal and plant life. In the past 50 years, significant Ring of Fire earthquakes have occurred in Indonesia, Chile, Japan and northern California.

The Juan de Fuca Plate also offers examples of sea-floor spreading and hot spots where it meets the Pacific Plate. A wide underwater mountain chain about 300 miles long (500 kilometers), known as the Juan de Fuca Ridge, marks their boundary. In the 1970s scientists discovered a valley at the top of this ridge where the sea floor is spreading apart. Along this rift there's a "hot spot" where magma from the Earth's core erupts below the ocean, forming new crust.

Volcanoes result when magma reaches the Earth's surface, often with explosive force. More than half of the world's currently active volcanoes circle the Pacific Ocean; hence its nickname, "Ring of Fire," according to a 1994 USGS Publication, "Volcanoes of the United States."  Most volcanoes are located along continental edges, such as Mount Rainier, Mount Hood and Mount St. Helens, which erupted spectacularly in 1980, disrupting life across much of the Western United States. Another volcanic eruption occurred at Mount Pinatubo in the Philippines in 1991, with much loss of life and property.

In some places, volcanoes erupt from beneath the sea and form island chains such as in Alaska's Aleutian Islands and the state of Hawai'i. In fact, the state's Mauna Loa volcano is the largest such geologic feature on Earth, covering half of the island of Hawai'i, also known as "The Big Island." Mauna Loa's summit rises 56,000 feet (17 kilometers) from its underwater base, with some 2 miles (more than 10,000 feet, or 4 kilometers) above sea level. Mauna Loa last erupted in 1984, and is carefully monitored by the U.S. Geological Survey.

With such lively activity occurring daily around the rim of the Pacific Ocean, it's no wonder that geologists keep close tabs on the Ring of Fire.

More about this author: Cynthia Astle

From Around the Web

  • InfoBoxCallToAction ActionArrow
  • InfoBoxCallToAction ActionArrow
  • InfoBoxCallToAction ActionArrow
  • InfoBoxCallToAction ActionArrow
  • InfoBoxCallToAction ActionArrow
  • InfoBoxCallToAction ActionArrow