What Is an Earthquake?

Ages 3-5 Simple Explanation

You know how if you push two blocks really hard against each other, sometimes one of them slips and everything shakes? That is kind of what happens during an earthquake! Deep, deep under the ground, giant pieces of rock are always pushing against each other very slowly. When they suddenly move, the ground above shakes — and that is an earthquake.

Some earthquakes are so tiny that you would not even notice them. Others are big enough to make things fall off shelves or make the floor feel like it is wiggling. The shaking usually only lasts a few seconds or a minute, even though it can feel a lot longer when it is happening.

If an earthquake happens, the safest thing to do is something called "drop, cover, and hold on." That means you drop to the ground, get under something strong like a table, cover your head and neck with your arms, and hold on until the shaking stops. Your teachers at school practice this so you know exactly what to do.

After the shaking is over, grown-ups check to make sure everyone is okay. Earthquakes can feel really surprising because they happen without any warning, but your family and teachers know how to keep you safe. If you live in a place where earthquakes happen sometimes, your family probably already has a plan — and that is a really good thing.

Ages 6-8 More Detail

An earthquake is when the ground shakes because of something happening deep under the Earth's surface. The Earth's outer layer is made up of giant pieces of rock called plates. These plates are always moving, but they move super slowly — only about as fast as your fingernails grow. Sometimes the edges of these plates get stuck against each other, and when they finally break free, the energy makes the ground above shake.

Earthquakes can feel very different depending on how strong they are. A small earthquake might just feel like a truck driving past your house — a low rumble and a small vibration. A bigger earthquake can shake the whole room, rattle windows, knock things off walls, and even crack roads or damage buildings. The strength of an earthquake is measured using a special scale.

Scientists who study earthquakes are called seismologists. They use special machines called seismographs to detect and measure shaking in the ground. These machines can pick up earthquakes happening on the other side of the world! Scientists know which areas are most likely to have earthquakes, but they cannot predict exactly when one will happen.

If you are inside during an earthquake, remember the rule: drop, cover, and hold on. Drop to the ground, take cover under a sturdy desk or table, protect your head and neck, and hold on until the shaking stops. Do not run outside during the shaking — things could fall on you. Once it stops, calmly move to an open area away from buildings.

Some parts of the world have more earthquakes than others. The edges of the Pacific Ocean, in an area called the "Ring of Fire," have the most earthquakes on Earth. That includes places like Japan, Chile, Alaska, and the west coast of the United States. If you live in one of these areas, your school probably practices earthquake drills, which is great because it means everyone knows what to do.

Earthquakes cannot be prevented, but buildings can be designed to handle them better. In places like California and Japan, many buildings are constructed to flex and sway instead of cracking when the ground shakes. This does not stop the earthquake, but it makes buildings much safer for the people inside.

Ages 9-12 Full Explanation

An earthquake is a sudden release of energy in the Earth's crust that causes the ground to shake. The Earth's surface is broken into massive slabs of rock called tectonic plates, and these plates are constantly moving — slowly drifting, pushing together, pulling apart, or sliding past each other. When the stress along the boundary between two plates builds up to the point where the rock can no longer hold, it breaks or slips, and the energy released radiates outward as seismic waves. Those waves are what you feel as shaking.

The point underground where the rock actually breaks is called the focus, and the spot on the surface directly above it is called the epicenter. Earthquakes are strongest near the epicenter and get weaker the farther away you are. Scientists measure earthquake strength using magnitude — the Richter scale is the one most people have heard of, though scientists now mostly use the moment magnitude scale. Each whole number increase means the earthquake is about 32 times more powerful. So a magnitude 7 earthquake is not just a little bigger than a 6 — it is enormously stronger.

Some of the most earthquake-prone regions on Earth sit along the Pacific Ring of Fire, a horseshoe-shaped zone that follows the edges of tectonic plates around the Pacific Ocean. California sits on the boundary between the Pacific Plate and the North American Plate, which is why earthquakes are common there. Japan, Chile, Indonesia, and Alaska are other hotspots. However, earthquakes can occur in unexpected places too — the central United States experienced some of the strongest earthquakes in American history in 1811 and 1812.

Engineers in earthquake-prone areas design buildings with special features to survive shaking. Some skyscrapers are built on massive rubber pads that absorb vibrations. Others have steel frames designed to flex without breaking. In Japan, some buildings use enormous rooftop pendulums that swing in the opposite direction of the shaking to keep the structure balanced. These innovations have saved countless lives by keeping buildings from collapsing during strong quakes.

Despite all our technology, scientists still cannot predict exactly when and where an earthquake will strike. They can identify zones where earthquakes are likely and estimate the probability of one happening within a certain number of years, but the precise moment remains unpredictable. This is why preparation is so important. If you live in an earthquake zone, your family should have an emergency kit, a communication plan, and a meeting point in case a quake hits when you are not all together.

The safety drill for earthquakes is simple but important: drop, cover, and hold on. Get low to the ground, crawl under a sturdy piece of furniture, protect your head and neck, and hold on until the shaking stops. Do not try to run outside during an earthquake — falling debris near buildings is one of the biggest dangers. After the shaking stops, be prepared for aftershocks, which are smaller earthquakes that follow the main one and can continue for days or even weeks.