Planet Earth is rather less quiet than many people would think. Even when it seems to be at its quietest, it is likely unleashing havoc (or failing that, at least mild inconvenience) somewhere else on its surface. Earthquakes are one of the ways our planet manifests its true restlessness. They can be caused by a variety of things, including volcanoes, human activity, and most commonly by movement at geologic faults in the Earth’s crust.
Roughly half a million detectable earthquakes take place every year worldwide. About one fifth of these are strong enough to be felt by people. About ninety percent take place in the geologically very active “Ring of Fire” surrounding the Pacific Ocean. The majority of really strong quakes take place in this area as well. Despite this, earthquakes may happen anywhere in the world, even in places where one wouldn’t immediately think of them occurring, like Europe or Middle America.
Most quakes are felt on the surface as a horizontal shaking. From my own experience, it is an occurrence that is comparable with sitting in a car that is being rocked and forth, laying on a mattress that one’s roommate is pushing with their foot, or suddenly and inexplicably finding oneself on a boat. This shaking isn’t violent or jerky, but a much smoother, more rolling sensation. I’ve only been aware of a few earthquakes and none of them were particularly violent, despite one of them being the recent 5.6 earthquake in central Oklahoma, which happened to be the largest in state history.
Though most quakes don’t cause much more damage than a few cracks in the ground and the odd broken plate, some can have disastrous effects. Often it isn’t only the quake itself that causes the worst of the damage or claims the most lives. If gas lines or electrical networks are compromised during a quake as they were in the 1905 San Francisco earthquake, fires can break out in the affected area. If water lines were also damaged in the quake, stopping these fires can be nearly impossible. Damage caused by earthquakes to things like nuclear reactors as in the case of the 2011 earthquake in Japan can also be potentially catastrophic and require immediate action by authorities to prevent the problem from spiraling out of control.