The Ring of Fire

The Ring of Fire is a horseshoe-shaped line of volcanoes and deep ocean trenches that runs around the Pacific Rim: from New Zealand up through Tonga, New Guinea, Indonesia, Japan, the Aleutian Island Chain, Alaska, and down the West Coast of Canada, the United States, Mexico, and Central America, finally ending where the southern end of Chile meets Argentina near Cape Horn at the tip of South America.

While doing research for my adventure novel TSUNAMI, I found that this highly unstable seismic zone is called the Ring of Fire for good reason. 90% of the world's earthquakes, over 70% of volcano eruptions, and most of the tsunamis on Planet Earth are spawned around the Pacific Rim, where oceanic (seafloor) plates collide with and relentlessly slide under the continental (land) plates.

The lithosphere is the name given to the earth's crust plus a portion of the earth's upper mantle, which is the layer just below the crust. In the theory of plate tectonics, the lithosphere is broken into 15 to 20 pieces called tectonic plates. Geologists can't seem to agree on the exact number. The plates range in size from only a few thousand square miles to hundreds of thousands of square miles. The crustal portion of continental plates averages approximately 22 miles in thickness. Oceanic plate crusts are 4 miles thick on average. Average thickness of the entire lithosphere is about 75 miles. Temperature at the base of the lithosphere is over 2300 F.

The tectonic plates float on the hot viscous material that makes up the asthenosphere, or lower portion of the earth's upper mantle, which is estimated to be about 250 miles deep. The floating plates are in constant, though very slow, motion. The rate of tectonic plate drift varies from about 1 inch per year to as high as 6 inches per year. Oceanic plates tend to drift into and gradually slide under the continental plates. This process is called subduction, and is the underlying cause of earthquakes, volcanoes, and tsunamis in the Ring of Fire.