The Ring of Fire is a string of volcanoes and earthquake sites all along the edges of the Pacific Ocean. About 9 out of 10 earthquakes happen on the Ring of Fire. Three-fourths of all active volcanoes on Earth are along the ring.

The Ring of Fire is shaped like an approximately 40,000 kilometers (25,000-mile) horseshoe. It contains 452 volcanoes. The ring stretches 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. A group of volcanoes in Antarctica close the ring.

Plate Boundaries?

The top layer of Earth is called the crust. The crust is split into huge slabs called tectonic plates, which are as large as continents. The plates are always moving, but they move very slowly. Sometimes they crash together, move apart or slide next to each other. The boundaries, or edges, of these plates form the Ring of Fire.

Convergent Boundaries

There are three types of plate boundaries. A convergent boundary is formed by tectonic plates crashing into each other. At these boundaries, the heavier plate can slip under the lighter plate. The rock underneath gets so hot that it melts. The liquid rock is called magma. The liquid rock rises through gaps in the crust over millions of years. When it reaches the Earth's surface, the magma creates volcanoes.

Divergent Boundaries

A divergent boundary is formed when tectonic plates pull apart from each other. The old crust pulls itself in opposite directions and liquid rock comes up from below. Then, cold seawater cools the rock. The new solid rock forms new crust.

Transform Boundaries

A transform boundary is formed when tectonic plates slide past each other. Parts of these plates break or slip as they rub against each other. The plates push forward and cause earthquakes. The gaps between these plates are called faults. Most of Earth's faults can be found along transform boundaries in the Ring of Fire.

The San Andreas Fault is one of the busiest 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. These are areas deep inside Earth. As heat rises from a hot spot, it melts the rock above it. The melted rock, or 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. The country of Indonesia is a group of islands between South Asia and Australia. Under Krakatoa, the denser Australian Plate is slipping beneath the Eurasian Plate.

Mount Fuji is Japan's tallest and most famous mountain. It is also a volcano. Mount Fuji sits at a "triple junction," where three tectonic plates come together.

The Ring of Fire's eastern half also has active volcanoes. Mount St. Helens is in the U.S. state of Washington. It lies on a weak section of crust. That makes it more likely to erupt.

Popocatépetl is one of the most dangerous volcanoes in the Ring of Fire. The mountain is one of Mexico's busiest volcanoes. It has erupted 15 times since 1519.