The top layer of Earth is an interesting place. Also known as the 'crust,' this thin, solid layer is much more than meets the eye. If Earth were an apple, the skin of that apple could represent the crust in terms of thickness and location. But unlike an apple skin, Earth's crust isn't one large piece covering the entire planet. Instead, it's broken up into many different pieces called tectonic plates that fit together like a large puzzle.
Also unlike the apple, underneath the solid crust is not a deliciously crispy interior. Instead, directly below the crust, we have a thick liquid layer called the mantle. Because it is liquid, the mantle flows and moves around, which moves the plates sitting on top like pieces of ice on a pond.
When the plates get moved around, they wreak havoc because they crash into, and pull apart from, and rub against each other. And as you can imagine, these interactions can do some pretty serious damage. On Earth, these tectonic events result in dangerous natural disasters around the world, like earthquakes, volcanoes, and tsunamis.
Earthquakes
Earthquakes can and do happen anywhere in the world, but the majority of them occur in a region known as 'The Ring of Fire.' As you'll learn a little later in this lesson, this is also where most of the world's volcanoes are found and where the name comes from.
The reason so many earthquakes occur in these areas is because this is where many of Earth's tectonic plates come together. Earthquakes begin deep underground along plate boundaries. Tension and pressure build up as the plates slide past and bump into each other and sometimes even stick together. Although the plate boundaries themselves may be stuck, the plates keep moving and pulling. Eventually, the pulling becomes too much and the plates suddenly break free from each other, causing an earthquake!
You can think of an earthquake like a game of tug-of-war. If you and your friend are both pulling on opposite ends of the rope and suddenly your friend lets go, all of that tension quickly leaves the rope and down onto the ground you go! An earthquake is very much the same - the plates get stuck together as they move, building up tension. Suddenly, the plates slip past each other and break free, sending that built-up tension through the ground in all directions.
