This is What Earth Does

Earthquake in Japan

By now you’ve heard about the  magnitude 8.9 earthquake that hit near the Japanese city of Sendai.  It has devastated the coastline, destroyed cities, homes, airports, and even cost an unknown number of people their lives. The aftershocks continue and the quake itself sent out tsunami waves across the Pacific basin. It’s an incredible experience and, for the people who are directly involved, it is horrifying.  I have spent some time today watching the videos and looking at the images and eyewitness accounts coming from Japan.  It is very sobering, as you can see from this video of tsunami waves in Japan

he underlying tectonic plates that make up the structure under Earth's surface. Note the Pacific Plate and the "ring of fire" that arcs around the northern part of the plate. Courtesy USGS via Wikimedia. Click to enlarge.

Earthquakes are what our planet does. They are a natural outgrowth of the way Earth is structured and anyone who has had even a beginning geology class in junior high or high school will have learned about them. I’ve already seen some speculation (wild-eyed, of course) that this quake was caused by the Moon, or is precursor to the coming apocalypse and a lot of other nonsense.  Perfectly understandable — when people don’t understand how something works, their fear leads them to assume some pretty outlandish things. But, in this case, the earthquake was caused by forces and processes that we understand from studying the geology of our planet.  It’s a purely natural, albeit horrifying and scary phenomenon.

An earthquake begins with the shifting of rock deep beneath the surface of the Earth. The shaking motion sends shock waves through nearby rock and up to the surface.  It happens all over our planet, but is a fairly frequent occurrence in this area of the world.

Here’s why:  Japan — indeed, the entire Pacific basin — is located on something called the Pacific Ring of Fire. The ring is really the edge of a large tectonic plate called the Pacific Plate.  It is moving, jostling if you will, against other tectonic plates and that slip-sliding/pushing action is what causes earthquakes. It’s that simple — plates of rock rubbing against each other.  The earthquake is simply a release of energy as the plates slip against each other. The rock moves, and that motion shakes the surface. Anything ON the surface is also moved — and often shaken to destruction, depending on the strength of the quake. In the case of this quake, it also sends huge releases of energy through the ocean, triggering tsunamis.

The so-called “ring of fire” is where heat and friction from those plate movements builds up volcanic structures — that is, it helps create volcanoes. Japan lies along that ring of fire, and as we’ve learned today, it rides along the earthquake belt — and sometimes, like today, pays the price for its location.

Earth has undergone earthquakes and tsunamis throughout most of its history. It will continue to do so each time the tectonic plates shift against each other and release the tremendous amounts of tension and energy that get stored up as they push against each other. Tectonics is fascinating topic. Today, it’s also an agent of destruction, and our thoughts go out to the people of Japan who have taken such a horrendous hit.