4 Facts About Earthquakes
Earthquakes are one of the most dangerous natural disasters. They can cause serious damage and even kill people. They can also be unpredictable. This is why it’s important to know some facts about them.
Earthquakes are caused by the movement of rock masses called tectonic plates. They often move together, but sometimes they get stuck and cause a big shift in the Earth’s surface.
1. They are caused by tectonic plates.
Tectonic plates are gigantic pieces of Earth’s crust and upper mantle that fit together like jigsaw puzzles at the planet’s fault lines. Most large earthquakes happen on or near the boundaries of these plates, which can be found around the world’s oceans and continents.
As the edges of plates move into each other in fault zones, friction slows down their motion and builds up stress over long periods of time. Then, suddenly, the plates jerk forward against each other and the stress is released in waves of energy known as earthquakes.
Some tectonic plates move faster than others, and these fast-moving plates tend to produce larger and more frequent earthquakes. In contrast, slow-moving tectonic plates may go for hundreds or even thousands of years between a large earthquake on their boundary. But these faults still accumulate elastic energy over time, and something has to give eventually. When it does, the plates may rupture suddenly and cause a big earthquake.
2. They are not affected by weather.
Earthquakes shake the ground and cause ground ruptures, which can damage buildings and other infrastructure. Liquefaction, which causes water to break out of its normal solid form and flow through cracks in the Earth, can also occur during earthquakes.
The forces that cause earthquakes are much larger than the wind, temperature and barometric pressure changes that we know about from weather observations on the surface. Even if there was a connection between weather and earthquakes, it would be very hard to detect because the earthquake waves travel miles underground.
Scientists do know that certain animals react to the presence of a coming earthquake. Rats, for example, panic and run away from people. Cockroaches frantically scatter, and freshwater fish swim up wildly in lakes and ponds. The reason for these reactions is that animals can pick up the vibrations of an upcoming earthquake, which are transmitted to the surface by the “P” and “S” waves. The shaking is recorded by seismometers, which are often buried to protect them from surface vibrations.
3. They are not predictable.
While scientists do have a pretty good idea how earthquakes work, they still can’t predict when or where one will happen. It’s like trying to predict when the weather will change in your area, but with far more destructive consequences.
Luckily, we can detect them using seismometers and seismographs, and sometimes even get a few seconds of warning. That’s enough time for people to drop, cover and hold on!
Earthquakes are also often followed by aftershocks, which are small earthquakes that occur in the lead up to the main shock. These can be as strong as the main quake itself, so it’s important to stay safe! Many animals also seem to sense an impending quake, with rats running around in fear and cockroaches frantically scrambling for the nearest hiding spot. Scientists think they may be picking up on weak tremors or even electrical signals that are triggered by shifting underground rocks.
4. They are dangerous.
Earthquakes occur on every continent, but most are so weak that they do not cause damage. Only a few are strong enough to be felt and the majority are not noticeable except for scientists with seismographs at specialized stations.
Most of the damage done by an earthquake is caused by secondary effects like fires and landslides. Buildings that are built on or near faults are most at risk, but even if buildings are not directly on the fault line they can be damaged from ground movement during an earthquake.
Earthquakes can also cause Tsunamis, a terrible natural disaster that wreaks death and destruction far from the epicenter. Other dangers include falling furniture, which can bruise or break a person; surface waves that make buildings heave and lurch; and liquefaction in which water saturated soil acts as though it were a liquid and swallows anything in its path. The strongest or “great” earthquakes are the ones that destroy cities and cause massive tsunamis.