The Pacific Ring of Fire

What was the first impression you got when you read the title of this article? If you thought that this is the name of the latest Oscar -winning movie, we are sorry to say that you are mistaken, although this is certainly an attractive name for a movie. However, when you realise what this is all about, a chill would run down your spine due to the devastating nature of this particular 'ring'.

This is not a magical ring such as the one Frodo had in the 'Lord of the Rings'. Instead, this is a huge region on our planet which is prone to some of the deadliest forces of Mother Nature. The Pacific Ring of Fire is an area of frequent earthquakes and volcanic eruptions surrounding the basin of the Pacific Ocean.

Although it is called a ring, the region is actually horseshoe-shaped, and is made up through the linking of an almost continuous series of oceanic trenches, volcanic arcs (part of a curve), volcanic belts and plate movements, spreading over a staggering 40,000 kilometres.

It is sometimes called the Circum-Pacific Belt or the Circum-Pacific Seismic Belt. Ninety per cent of the world's earthquakes and 81 per cent of the world's largest earthquakes occur along this Ring of Fire.

The rest of the earthquakes happen in the Alpide belt, which extends from Java to Sumatra through the Himalayas, the Mediterranean out into the Atlantic and the Mid-Atlantic Ridge. The Ring of Fire is a result of the movement and collision of the plates of the crust of the Earth.

Major volcanic areas in the Ring of Fire

* In South America - The Nazca plate is colliding with the South American plate, which has created volcanoes such as Cotopaxi and Azul.

* In Central America - The Cocos plate is colliding with the North American plate and has formed the Mexican volcanoes of Popocatepetl and Paricutun which interestingly, rose up from a cornfield in 1943 and became an instant mountain.

* Between Northern California and British Columbia - The Pacific, Juan de Fuca, and Gorda plates have built the Cascades and the well-known Mount Saint Helens, which erupted in 1980.

* Alaska's Aleutian Islands are growing as the Pacific plate presses against the North American plate. The Aleutian Trench with a maximum depth of 25,194 feet has been created at the subduction zone (explained under Trivia).

* From Russia's Kamchatka Peninsula to Japan, the subduction of the Pacific plate under the Eurasian plate is responsible for Japanese islands and volcanoes such as Mt. Fuji.

* The Indo-Australian plate subducts under the Pacific plate and has created volcanoes in the New Guinea and Micronesian areas. The Pacific Plate slides under the Indo-Australian plate near New Zealand.

Trivia

* What is an oceanic trench?

Oceanic trenches are long, but narrow depressions of the sea floor. They are also the deepest parts of the ocean floor.

* What is a dormant volcano?

It is a volcano which is not currently active, but may erupt at some point in the future.

* What is a volcanic arc?

It is a chain of volcanic islands or mountains formed by plate tectonics as an oceanic tectonic plate subducts under another tectonic plate and produces magma. There are two types of volcanic arcs named oceanic arcs and continental arcs.

* What is a volcanic belt?

A volcanic belt is a large volcanically active region. Volcanic belts are similar to a mountain range, but the mountains within the range are volcanoes and not actual mountains that are formed by the movement of tectonic plates.

* What is the lithosphere of a planet?

The lithosphere is the solid outermost shell of a rocky planet.

* What is meant by plate tectonics?

It is a theory of geology that has been developed to explain the observed evidence for large-scale motions of the Earth's lithosphere.

* What is subduction?

It is a phenomenon (happening) where two tectonic plates meet and move towards one another, with one sliding underneath the other and moving. These happen very slowly at rates typically measured in centimetres per year.

Aravinda Dassanayake