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Friday, October 24, 2014

Typhoons and Earthquakes in the Philippines

The Philippines has more than its fair share of disasters, and not because the country is particularly cursed or anything, but because the entire archipelago—purportedly composed of 7,100 islands—lies on a region in the Pacific Ocean called the “Ring of Fire” (actually, the area is shaped more like a horseshoe, although to be fair, “The Horseshoe of Fire” doesn’t have the same impact as the “Ring of Fire”). About 40,000 kilometers long, the “ring” runs from the southern tip of South America, up along the coast of North America, across the Bering Strait, down through Japan, the Philippines, Indonesia (the Ring of Fire’s western edge extends into the Indian Ocean), and to New Zealand.  The “Fire” part of the Ring of Fire is because a string of 452 volcanoes dot this line, like a malevolent game of connect-the-dots.


The regions along this line experience volcanic eruptions and periodic earthquakes—majority of them small, hardly-felt tremors, and the few devastating ones that kill thousands and cause tsunamis that can kill even more.
Besides being right on the edge of the Ring of Fire, the Philippines is also practically next door to an area in the Pacific where typhoons regularly spawn.
And, as luck would have it, the country is right in the typhoons’ path—a sort of doormat for typhoons as they make their way towards the Asian mainland.

This means that besides molten rocks and earthquakes, the Philippines also experiences weapons-grade winds that can tear down homes, uproot trees, cause storm surges, as well as torrential rains that can trigger flashfloods, landslides, and destroy crops and properties.
Approximately 80 typhoons develop in this region yearly, and about 19 enter the Philippine Area of Responsibility (PAR). About six to nine of these typhoons make landfall, making the Philippines the country most exposed to typhoons.   
No wonder our country is among the world’s most disaster-prone countries.

 

Right On Top of Plates

Tectonic plates, I mean.
These are part of the Earth’s mantle—massive, irregularly shaped slabs of solid rock just under the planet’s surface, upon which large section of the Earth rests. They are called tectonic plates by scientists.
There are about 8 major plates, and dozens of smaller ones, each carrying a piece of the world on top, making our planet seem like a gigantic jigsaw puzzle.
Tectonic plates vary greatly, from a few hundred to thousands of kilometers across. The Pacific Plate and the Antarctic Plates are the largest. Each plate’s thickness also varies, ranging from less than 15 kilometers to about 200 kilometers or more. The plates constitute the lithosphere, which is a layer of rock on the top of the Earth’s mantle.


Beneath the lithosphere is a partially molten rock layer called asthenosphere. Driven by forces from deep beneath the earth, the plates slowly move across the planet’s surface, interacting with other plates, diverging, colliding, and slipping past each other. The edges of these plates, where they bump and grind against other plates, are the sites where earthquakes commonly happen, and where many volcanoes are active.
These movements also influence the form of the planet’s surface. Where the plates meet, mountain-building occurs—besides earthquakes, volcanic activity, and oceanic trench formation.
According to the plate tectonics theory, Earth’s outer shell is divided into several plates that glide over the rocky inner layer above the core called the mantle. Actually a modern version of Alfred Wegener’s Continental Drift Theory first proposed in 1912, this theory explains how the Earth’s continents move around the planet. Tectonic plates probably developed very early in the Earth’s 4.6-billion-year history. They have been drifting since, pressing against each other, then separating again, like some fiery and explosive dance that has been going on since the beginning of time, in the process forming and shaping the world as we know it.
The plates move about the same rate as the growth of your fingernails, so the world that we know today is different from what it was millions and millions of years ago. And millions and millions of years from now, the world will wear a face unrecognizable to us.
Most of the boundaries between individual plates are hidden beneath the oceans, so they cannot be seen. They can be accurately mapped, however, from outer space by measurements from satellites. 
Plates change over time, like many features on the surface of the Earth. Plates that are composed of denser materials, like an oceanic lithosphere, can sink under a lighter continental plate, and can eventually disappear completely. There are actually plates that are in danger of disappearing.
The Philippines, as we have mentioned, is in the Pacific Ring of Fire, where the oceanic Philippine Plate and a few much smaller plates are subducting, or sliding under, along the Philippine Trench. Moreover, scientists consider the Philippine Sea plate as unusual, because almost all the boundaries of the surrounding plates are converging.
This means that the country is being squeezed by two large tectonic plates—the Pacific Plate and the Eurasian Plate.


Note: This is an excerpt from my forthcoming book, "Disaster Management for Filipinos"

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