How Earthquakes Work

There are times when the earth isn't as stable as it seems. And it just kept coming. And I kept coming and I kept coming again. And it was like riding a roller coaster. It was really a rocking and rolling. I just, in my wildest imagination, had no comprehension that mother nature can be that destructive and just every year more than a million earthquakes rattle our world. We don't notice most of them, but the ones we do give us new respect for our planet. Earthquakes happen when tension stored in the earth's crust is suddenly released. To understand what causes these disasters, we need to travel to the center of the earth. The enormous heat and energy here shapes the layers above, especially the earth's outer crust. We can think of the crust as a jigsaw puzzle divided into about 12 tectonic plates. These giant slabs of rock hold the continents and the ocean floor. For millions of years they've been drifting and colliding, pushed by the churning liquid mantle below. When they slip, grind and crunch past each other, disasters occur. Some of the worst quakes happen when the plates get stuck and pressure builds. When they finally break free, energy is released as waves traveling through the ground. Geologist David Schwartz describes the process. The plates are moving past each other, they're pushing against each other when the stress fills up to a critical point, they snap, and the snapping, of the plates, basically, produces the seismic waves that that's the earthquake. These disasters usually occur at the boundaries between two plates. This is where we find faults, cracks, and fractures in the earth's crust, where the plates inch along, geophysicist raw Stein explains. These faults typically at their base, let's say ten miles down, are moving at a few inches a year, and when that earthquake occurs, when that rupture begins, that fault, that motion is going to accelerate from a few inches a year to about 5000 miles an hour, and it's going to do that in three seconds. So this rupture of the fault is a catastrophic process. Unlike hardly anything else in nature. Like ripples in water, the vibrations spread out in all directions, shaking everything in their path. The strongest shaking occurs at the epicenter, the place on the earth's surface directly above the spot where the earthquake began. One of the worst quakes on record struck Alaska in 1964. It measured 8.5 on the Richter scale, a scale that measures the magnitude of a quake, the shaking lasted around four minutes, which is a long time for an earthquake. The ground ripped open, and in some places, sank more than 50 feet. We know how earthquakes happen and the great destruction they create. But unfortunately, we still can't predict them.