Quakes stir 'Ring of Fire'

2005-04-14 07:43

Indonesia - Massive quakes in Indonesia have stirred two huge volcanoes from their slumber and sent shockwaves reverberating along a vast and volatile region known as the Pacific 'Ring of Fire'.

Both on land or underwater, the volatile edges of the north Pacific, bounded by the east Asian rim and the west coast of the Americas, are alive with near-constant seismic activity.

Some of the most dramatic natural disasters of recent history have happened within the Ring's arc, which stretches from Chile, north to Alaska and then west to encompass Japan, Southeast Asia and the Pacific islands.

From the nuclear-like explosion of Krakatoa volcano off Indonesia in 1883 to the eruption of Mount St Helens in the United States in 1980, the Ring's awesome power is legendary.

But it gained new notoriety when on December 26 last year, a massive 9.3 magnitude earthquake occurred off Indonesia unleashing tsunamis that devastated shores around the Indian Ocean, killing more than 220 000 people.

The reason for such geological volatility is the fragile fault lines that ring the zone.

In constant motion

The earth's crust is made up of a series of rocky plates that literally float on the molten rock of the earth's mantle and core, interlocked over the entire planet like the pieces of a puzzle.

These plates are in constant motion, clashing into each other or moving away from each other, creating stresses and pressure build-ups at their margins.

The edges, or fault lines, are weak points in the planet's surface where the crust drops to just a few miles in thickness; at its thickest it is about 20 miles deep.

Many, mostly small eruptions occur, but occasionally huge volcanic explosions, earthquakes or landslides are generated, as pent up energy is released through the weak fissures.

Among the most active parts of the ring is the Mariana Trench, near the tiny US-controlled Guam islands, and in recent months, the waters off the southwestern shores of Indonesia's Sumatra island.

Last December's massive quake was created when the earth's crust shunted a huge 15 metres, producing so much energy that the planet wobbled on its axis and tsunamis travelled for thousands of miles.

That quake was followed three months later by another measuring 8.7 on the Richter scale, causing extensive damage to the Sumatra coast islands of Nias and Simeulue, leaving more than 670 dead.

Tremors have continued to shake the region, the latest on Wednesday measuring 5.3, with scientists warning that a third big seismic event could be on the way.

"The probability of a third quake in the coming months and years, cannot be excluded," Mustapha Meghraoui, of the Institute for Planetary Physics in Strasbourg, eastern France, said recently.

- SAPA