The Pacific Ring of Fire gets its name from the numerous volcanoes that lie on its rim. The highest number of earthquakes in the world has been recorded there, so it represents a constant danger for countries like Japan and Indonesia.
The devastating earthquake that struck Japan on Monday, with dozens more aftershocks, is just the latest in a series. That country is located in a dangerous area - the most dangerous in the world.
The extent of the Pacific Ring of Fire
It is a series of at least 450 active and temporarily inactive volcanoes along coastal areas, throughout the Pacific Ocean. The semicircular chain of volcanoes starts with a branch in the Indian Ocean, goes through Indonesia, Sumatra, Malaysia all the way to the Philippine Plate.
From that place, the Ring includes the entire Pacific plate, and the Juan de Fuca plate that lies in front of the Canadian coast and the coast of the American states of Washington and Oregon, then the Cocos plate (in the Pacific in front of Central America) and the Nazca plate in front of South America. High seismic activity is recorded along the entire area.
To what extent are people at risk?
Approximately 90 percent of all earthquakes in the world are recorded within that Ring. This means that people in Indonesia, the Philippines, Malaysia, Japan and Australia, as well as people in the island states of Malaysia, Micronesia and Polynesia, have to live under constant threat. Likewise, people along the entire North American and South American Pacific coast are affected by this phenomenon.
However, the danger is not the same for everyone. It is greater at higher altitudes or near tectonic plate boundaries. The real danger to people in those areas depends on the construction method and preventive measures for catastrophic earthquakes.
There is also a danger of tsunamis along the coast. Giant waves caused by earthquakes or volcanic activity can wipe entire coastal areas off the face of the earth in the shortest possible time.
Volcanoes that are close to settlements are dangerous in themselves. Eruptions emit toxic gases, dust and lava, and cause landslides.
Why are there so many volcanoes along this line?
The tectonic plates that make up the Earth's mantle are constantly moving on a bed of partly solid and partly molten rock. Where the plates collide, or break away from each other, the earth literally moves.
Where the earth cracks, volcanoes can form. This is the case with Hawaii, in the middle of the Pacific plate. However, the largest number of volcanoes are located at the collision points of tectonic plates. This is how, for example, mountain ranges such as the Andes in South America or the Rocky Mountains in North America were created.
What is subduction?
This term from the domain of geology denotes the subduction of one tectonic plate under another - it sinks under it, that is, it is subducted. This is also happening on the Pacific Ring of Fire. A plate subducting under another puts enormous pressure on the magma in the interior of the earth, so it looks for a way to the surface through the cracks. This is how volcanoes are formed.
If an ocean lies across such a place, volcanic islands can form. This is how the Mariana Islands were formed on the border of the Philippine and Pacific plates.
When were the strongest earthquakes recorded along the Ring?
On May 22, 1960, an earthquake of 9,5 degrees on the Richter scale was recorded in Chile. The United States Geological Survey considers it the most powerful earthquake recorded since 1900.
In second place is the earthquake in Alaska in 1962, which had a magnitude of 9,2 on the same scale. In third place is the earthquake recorded in December 2004 in North Sumatra. It measured 9,1 on the Richter scale and caused a catastrophic tsunami in the Indian Ocean.
The earthquake on the seabed off the Japanese coast near Honshu in March 2011 had the same intensity - it also caused a tsunami and thus the nuclear disaster in Fukushima.
The earthquakes on this list most often fall into the category of earthquakes above 8,5 on the Richter scale, and the largest number of them occurred on the Pacific Ring of Fire.
Why is it hard to predict earthquakes?
Despite close scientific monitoring of tectonic plate movements and volcanic activity, earthquakes cannot be accurately predicted. Even when two earthquakes occur within a short period of time, it is difficult to establish whether they are related.
There are seismologists who discuss the possibility that some human activities, such as the extraction of ore, oil and gas or underground atomic tests, cause earthquakes. But it is difficult to prove scientifically unequivocally.
It is clear that the Pacific Ring of Fire is under constant pressure. When an earthquake occurs somewhere, the pressure eases for a while, but soon rises again.
People living in such areas can only do what is in their power - to adapt the construction of their settlements to the constant danger, to avoid living on the very coast and to build early warning systems, in order to escape in time before the tsunami.
They must store materials, water and food in safe places, so that life can continue even after the next disaster.
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