The Ring of Fire is a string of volcanoes and earthquake sites around the edges of the Pacific Ocean. Roughly 90 percent of all earthquakes occur along the Ring of Fire. The ring is dotted with 75 percent of all active volcanoes on Earth.

The Ring of Fire is shaped like an approximately 40,000 kilometer (25,000-mile) horseshoe and contains 452 volcanoes. These volcanoes stretch from the southern tip of South America, up along the coast of North America, over to eastern Russia, down through Japan and into New Zealand. Several volcanoes in Antarctica close the ring.

Plate Boundaries?

The Ring of Fire is the result of huge slabs of Earth's crust called tectonic plates. The plates are constantly moving atop a layer of solid and liquid rock called the mantle. The mantle is the layer between the Earth's crust and core. Sometimes the plates that move in the mantle layer crash together, move apart or slide next to each other.

Convergent Boundaries

A convergent plate boundary is formed by tectonic plates crashing into each other. At these boundaries, the heavier plate can slip under the lighter plate. The dense mantle material turns into magma or hot liquid rock. The magma rises through the crust to Earth's surface over millions of years. This creates a series of active volcanoes.

At the bottom of the Pacific Ocean, there is a series of deep ocean trenches that run parallel to volcanoes along the Ring of Fire. These create both islands and continental mountain ranges.

Divergent Boundaries

A divergent boundary is 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.

Transform Boundaries

A transform boundary is formed as tectonic plates slide past each other. Parts of these plates get stuck at the places where they touch, causing the rock to break or slip. The plates push forward and cause earthquakes. These areas of slippage are called faults. 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 California.

Hot Spots

The Ring of Fire is also home to hot spots, which are high-temperature areas deep inside Earth. As heat rises from a hot spot, it melts the rock above and turns it into magma. The magma often pushes through cracks in the crust to form volcanoes.

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 slipping under the Eurasian Plate. An eruption in 1883 destroyed the entire island. It sent volcanic 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 is Japan's tallest and most famous mountain. It is also an active volcano. 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 weak section of crust, which makes it more likely to erupt. 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. Twenty million people live close enough to Popocatépetl to be threatened by a destructive eruption.