Earthquakes 101 | National Geographic
The ground starts to quiver; glasses rattle. Soon, walls shift, and everything begins to collapse—telltale signs of what could be a devastating earthquake. We've seen the destruction they unleash. Some of us may have even lived through one, and we know they can be deadly. But where does this mountain-moving force come from?
While we may think we're standing on solid ground, the earth beneath us isn't completely stable at all. Our planet's crust is made up of about 12 major tectonic plates that fit together like a giant jigsaw puzzle. These huge slabs of land float on superheated magma and constantly shift, bump, and grind against one another. It's there, along the seams where earthquakes tend to happen, when friction between the two plates is violent enough. Seismic shock waves ripple through the ground, rattling everything that stands on it. The stronger and shallower the quake, the more violent the destruction.
The most violent type of earthquake is born in a subduction zone, where one tectonic plate is shoved beneath another. While one plate is forced downward into the mantle, the other juts upward, often violently. This is a type of quake that rocked Nepal in May 2015. When subduction happens under the ocean, it can create giant, unstoppable waves called tsunamis, like the ones that killed hundreds of thousands in Japan and Indonesia.
On average, earthquakes kill about 10,000 people each year; sometimes, numbers are far higher. The quake that hit Haiti in 2010 killed more than 300,000, by some counts, making it one of the deadliest on record. It is estimated that there are 500,000 detectable earthquakes in the world each year. One hundred thousand of these can be felt, and 100 of them cause damage—that's about 0.1%.
The magnitude of an earthquake is measured using the Richter scale, which runs from 0 to 10, 10 being the strongest. Every whole number increase on the scale means 10 times more ground motion. In recorded history, the world has never experienced a 10 on the Richter scale, but scientists predict an average of at least one major quake of magnitude 8 or higher every year.
The fact is, the Earth's crust is restless and always on the move. We can't see earthquakes coming, but we can prepare for them. Engineers are now designing stronger buildings resilient enough to survive a direct hit. Scientists are crunching data to project the power of future quakes and anticipate when and where they can strike next. Right now, we can only estimate the probability an earthquake will occur, but perhaps one day we will learn to predict them, minimizing their destruction and saving countless lives.