The Ring of Fire has a total of 452 volcanoes, and has 75% of the Earth's active and dormant volcanoes. The whole Ring of Fire stretches for 40,000 km in length.
The Ring of Fire is created by the Earth's plate tectonics. The Earth's crust is broken up into plates which float on top of the mantle. When these plates come together, you can get volcanoes and earthquakes. The eastern side of the Ring of Fire has the Nazca Plate and the Cocos Plate being subducted (going underneath) the South American Plate. And in the North, the Pacific Plate and the Juan de Fuca Plate are being subducted underneath the North American Plate. The Pacific plate is also subducting underneath the Kamchatka Peninsula and Japan.
Because of all this subduction, there are many cracks in the Earth's crust where magma can reach the surface and erupt as volcanoes. There are volcanoes in Chile, Mexico, the United States, Canada, Russia, Japan, the Philippines, Indonesia, New Zealand and Antarctica.
Some of the most famous volcanoes on Earth are in the Ring of Fire. Mount St. Helens, which erupted in 1980 is a good example, or Mount Rainier in Washington State, or Mount Shasta in California. The recent eruption of Mount Redoubt in Alaska is part of the Ring of Fire. And so are Mount Pinatubo in the Philippines and Mount Fuji in Japan.
The Ring of Fire has produced more than just volcanoes. It has also created islands and mountain chains around the Pacific Ocean. The Aleutian Islands in Alaska are all volcanic, and Japan is part of the subduction of the Pacific Plate going underneath the Eurasian Plate.
We usually can't feel the slow movement of Earth's rocky tectonic plates beneath our feet. But where they crunch into each other, all that slow movement produces some dramatic effects, especially around the Pacific Ocean, in the volcanic, quaking Ring of Fire.
The Pacific Ocean covers almost a third of our planet. It is larger than all the dry land on Earth combined. Pacific means "peaceful," but the edges of this ocean are anything but calm. Half of Earth's active volcanoes above sea level, and most of the world's earthquakes, happen around the Ring of Fire.
No one could explain what made the Ring of Fire so active until the 1960s, when scientists solved the puzzle of the moving continents. Then they realized that the volcanoes were erupting along the edges of an enormous plate of rock that makes up the floor of the Pacific Ocean.
Sinking Plates, Big Waves, and Quakes
Most of the drama of the Ring of Fire happens deep underwater, as the Pacific plate pushes against other plates around its edges. The Pacific plate is denser and heavier than those around it. As it pushes against them, its edges slide underneath in a process called subduction.
But the jagged edges of tectonic plates don't slide smoothly when they collide. Instead, they build up pressure and then suddenly snap, like a stuck door that finally gives way. The snap, releasing all that pent-up energy, is an earthquake, and the Pacific plate causes lots of them. Small earthquakes (too small to feel) happen all the time. Strong quakes can shake down buildings and cause tsunamis, powerful waves that travel as fast as an airplane across the ocean and can flood coasts. In December 2004, the second-largest earthquake ever measured created a colossal tsunami in the Indian Ocean, sending waves 100 feet (30 meters) high onto towns from Thailand to Africa.
Deep ocean trenches form where the edges of the Pacific plate dive under the plates next to them. The deepest is the Mariana Trench, stretching from Guam to Japan. This gash in the ocean floor drops almost 7 miles (11 kilometers) down, nearly three times as deep as the rest of the ocean.
Volcanoes Above and Below
More than 450 above-ground volcanoes erupt around the edges of the Pacific plate. There are even more under the water. These volcanoes form as pressure from the plate pushing into its neighbors squeezes magma (molten rock) up from the lower layer, called the mantle. Volcanoes have made many islands and island chains around the Ring of Fire. The Aleutians (off the coast of Alaska), the Philippines, and the islands of Japan are all volcanic island chains that formed in this way.
At the center of the plate, where it is pulling apart in opposite directions, underwater volcanoes also bubble and boil. Magma seeps up through cracks in the seafloor. As it cools, this magma builds up long undersea mountain ranges, called mid-ocean ridges. The new seafloor shoves the older seafloor out toward the plate's edge. There, the oldest seafloor is pushed under again, to heat up and melt back into magma.
This seafloor recycling, from mid-ocean ridge to plate edge and back, works like a giant conveyor belt, destroying and rebuilding Earth's rocky outer layer.
Volcanoes also form over "hot spots" in Earth's mantle, where tubes of hot magma rise to the surface. Hot spots don't move (much), but the drifting ocean plate moves over them, making a line of volcanoes. This is how the Hawaiian Islands formed. Kauai, the oldest island, is now the farthest northwest. The youngest island, the Big Island of Hawaii, now sits on top of the hot spot. Lava flows from Hawaii's volcanoes continue to add new land on the southern side of the island.
Life in the Deeps
Despite its dangers, the Ring of Fire is home to a rich and surprising variety of life in the most unexpected places. Deep underwater, in utter darkness, where scientists once thought nothing could live, volcanic activity sends clouds of super-hot, mineral-rich water spewing from cracks in the seafloor called hydrothermal (hot-water) vents. The minerals build up rocky chimneys that offer a toehold for bacteria that don't need oxygen to live. Instead, they breathe sulfur from the hot water.
These bacteria are at the bottom of a food chain of animals that don't live anywhere else: bizarre giant tube worms, jellyfish that look like dandelions, pale anemones, clams the size of dinner plates, and ghostly white crabs. Tube-worm fossils more than a million years old prove that these hot vent communities have been around for a long time. Many scientists think the earliest life on Earth, more than a billion years ago, may have looked like this.
Living with the Ring of Fire
Scientists living around the Ring of Fire have long searched for ways to predict its earthquakes, volcanic eruptions, and tsunamis. Sensitive machines called seismometers are used to measure movement underground and stresses that might cause quakes. But no one is yet found a foolproof way to predict earthquakes. It's like trying to guess when a tottering stack of blocks is going to fall: the more time passes, the more likely it is to happen, but it's very hard to tell exactly when. For now, the best way to stay safe from quakes is to build strong, flexible, shake-proof buildings.
Predicting tsunamis is easier, since earthquakes cause them. The Pacific Tsunami Warning Center (PTWC) in Ewa Beach, Hawaii, monitors the ocean for tremors that might trigger a tsu- nami. Systems like this can warn people in danger zones many hours before the monster waves make landfall, giving them time to get to higher ground.
Ring of Knowledge
Although we may not be able to feel the continents move, in the Ring of Fire we can see the dramatic effects, as Earth reshapes itself before our very eyes. From volcanoes to vent communities, Earth's largest plate and its ocean have taught us a lot about our restless planet.
Copyright Carus Publishing Company Jul/Aug 2009
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