What Causes Earthquakes and How Are They Measured?

Earthquakes happen when parts of Earth move suddenly, like when you push your friend off a swing.

Bold key terms: When big pieces of Earth called plates move, they can shudder and cause the ground to shake. This shaking is an earthquake.

Imagine pushing on a table from both sides, if it's not steady, it might squeak or even tip over. That’s kind of like what happens underground. The Earth's plates are like giant puzzle pieces that slowly move. When they get stuck and then suddenly slip free, the ground shakes, just like your table.

People use a tool called a seismometer to measure earthquakes. It works like a super-sensitive swing: when the ground moves, it swings too. The bigger the shake, the more it swings, and that tells scientists how strong the earthquake was.

Sometimes we say the earthquake is a 5, or a 7, just like you might rate your favorite ice cream! The number is called the magnitude, and it helps us know how big the shake really was.