Why does the ground shake?

 

Why does the ground shake?

Huge pieces of rock called plates make up the surface of the Earth. These plates move around, and sometimes get stuck as they try to move past each other. When rock moves suddenly, the ground shakes, creating an earthquake. Earth’s plates move a few centimeters every year. This is the same speed fingernails grow.

 

Fault lines

Cracks along large areas of rock are called faults. They can be massive plate boundaries or smaller cracks in other places

 

Flexible rock

Rock can stretch and bend as it moves. Sometimes it springs back into place, making the Earth shake.

 

Types of plate boundaries

Boundaries are areas where huge slabs of rock meet and move. Plates move in three different ways at these boundaries.

 

Apart

Plates pulling away from each other.

Liquid rock flows out between the plates.

 

Together

Plates push toward each other.

One plate is forced below the other.

 

Along

Plates slide past each other.

Tremors occur where plates rub against each other.

 

Where do earthquakes happen?

 

Plate boundaries

Earth’s surface is broken into huge chunks of rock called tectonic plates. Most earthquakes happen in places where the tectonic plates rub together.

 

Quick quiz

1. Which machines are used to measure earthquakes?

2. What is the name of the scale used to measure earthquakes?

3. What are the three main ways tectonic plates move?