TheRing of Fireis a string ofvolcanoes and sites ofseismicactivity, or earthquakes, around the edges of the Pacific Ocean. Roughly 90 percent of allearthquakes occur along the Ring of Fire, and the ring is dotted with 75 percent of allactive volcanoes on Earth.
The Ring of Fire is shaped like an approximately 40,000 kilometer (25,000-mile)horseshoe. A string of 452 volcanoes stretches from the southern tip of South America, up along thecoastof North America, across theBering Strait, down through Japan and into New Zealand. Several active andinactive volcanoes in Antarctica, however, close the ring.
Plate Boundaries?
The Ring of Fire is the result of tectonic plates, huge slabs of Earth'scrust that fit together like pieces of a puzzle. The plates are constantly moving atop a layer of solid andmolten rockcalled themantle. Sometimes these platescollide, move apart or slide next to each other.
Convergent Boundaries
Aconvergent plate boundaryis formed by tectonic plates crashing into each other. Convergent boundaries are oftensubduction zones, where the heavier plate slips under the lighter plate, creating a deeptrench. This subduction changes thedensemantle material into magma or liquid rock. The magma rises through the crust to Earth's surface over millions of years, creating a series of active volcanoes known as avolcanic arc.
If you were to drain the water out of the Pacific Ocean, you would see a series of deep ocean trenches that runparallelto volcanic arcs along the Ring of Fire. The arcs create bothislands andcontinentalmountain ranges.
The Aleutian Islands in the U.S. state of Alaska, for example, run parallel to the Aleutian Trench. Both geographic features continue to form as the Pacific Platesubducts beneath the North American Plate. The Aleutian Islands have 27 of the United States' 65 historically active volcanoes.
Divergent Boundaries
Adivergent boundaryis formed by tectonic plates pulling apart from each other. Magma wells up as the old crust pulls itself in opposite directions, then cold seawater cools the magma, creating new crust. The upward movement and eventual cooling of this magma has created high ridges on the ocean floor over millions of years.
Transform Boundaries
Atransform boundaryis formed as tectonic plates slidehorizontally past each other. Parts of these plates get stuck at the places where they touch, causing the rock to break or slip, suddenlypushing the plates forward and causing earthquakes. These areas of breakage or slippage are calledfaults. The majority of Earth's faults can be found along transform boundaries in the Ring of Fire.
The San Andreas Fault is one of the most active faults on the Ring of Fire. It lies on the transform boundary between the North American Plate and the Pacific Plate. Measuring about 1,287 kilometers (800 miles) long and 16 kilometers (10 miles) deep, the fault cuts through the western part of California. Movement along the fault caused the 1906 San Francisco earthquake, which destroyed nearly 500 city blocks.
Hot Spots
The Ring of Fire is also home tohot spots, areas deep inside Earth's mantle from which heat rises. This heatmelts the rock above it. The melted rock, known as magma, often pushes through cracks in the crust to form volcanoes.
Mount Erebus, the most southern active volcano on Earth, sits over the eruptive zone of the Erebus hot spot in Antarctica. It has been consistentlyerupting since it was first discovered in 1841.
Active Volcanoes In The Ring Of Fire
Most of the active volcanoes on the Ring of Fire are found on its western edge.Krakatoa is an island volcano in Indonesia. Beneath Krakatoa, the denser Australian Plate is being subducted beneath the Eurasian Plate. An eruption in 1883 destroyed the entire island, sendingvolcanic gas,volcanic ash, and rocks as high as 80 kilometers (50 miles) in the air. A new island volcano, Anak Krakatau, has been forming with minor eruptions ever since.
Mount Fuji, Japan's tallest and most famous mountain, is an active volcano in the Ring of Fire. Mount Fuji last erupted in 1707, but recent earthquake activity suggests it could erupt again. Mount Fuji sits at a "triple junction," where three tectonic plates interact.
The Ring of Fire's eastern half also has a number of active volcanic areas. Mount St. Helens is an active volcano in Washington state. It lies on a particularly weak section of crust, which makes it moreproneto eruptions. Its historic 1980 eruption lasted nine hours and covered nearby areas in tons of volcanic ash.
Popocatépetl is one of the most dangerous volcanoes in the Ring of Fire. The mountain is one of Mexico's most active volcanoes, with 15 recorded eruptions since 1519.Located close to Mexico City and Puebla, 20 million people live close enough toPopocatépetl tobethreatened by adestructiveeruption.
Fast Fact
Cooling Ring
The Pacific Plate, which drives much of the tectonic activity in the Ring of Fire, is cooling off. Scientists have discovered that the youngest parts of the Pacific Plate (about two million years old) are cooling off and contracting at a faster rate than older parts of the plate (about 100 million years old). The younger parts of the plate are found in its northern and western parts—the most active parts of the Ring of Fire.
Fast Fact
Jolting Japan
The island nation of Japan lies along the western edge of the Ring of Fire, and is one of the most tectonically active places on Earth. As much as 10 percent of the world’s volcanic activity takes place in Japan.
