What Causes Earthquakes


What Causes Eathquakes Earthquake Information Earthquake Facts for Kids Effects of Earthquakes

This video includes:
What Causes Earthquakes?
Earthquake Information
Earthquake Facts for Kids
Earthquake Information
Earthquake Definition
How do earthquakes occur?
How to earthquakes happen?
Earthquake Effects
What is earthquake?
Natural Disasters

What causes eathquakes?
The earth is made up of four layers – the inner core, outer core, mantle and crust.
The mantle and crust are a thin skin compared to the other layers.
The mantle is about 1,800 miles thick, while the crust is only about 8 miles thick.
This thin skin is broken into pieces called tectonic plates.
The plates are like puzzle pieces, floating on top of the Earth’s inner core. Sometimes the pieces slide under or against each other and become stuck.
When the pieces slide apart, they create tremendous force. This force causes the earth to shake and ripple.

How do you measure earthquakes?
Instruments called seismographs are used to measure how large the earthquake was.
The instrument uses a weighted pen and a spring and the vibrations from the earthquake makes the pen draw lines onto some paper.
A short wiggly line that doesn’t wiggle very much means a small earthquake, and a long wiggly line that wiggles a lot means a large earthquake.

What is the Richter Scale?
Scientists measure earthquakes using the Richter scale. This scale, invented in 1934 by California scientist Charles Richter, measures the magnitude of an earthquake, and the result is a number from 0 to 10. It is measured on a machine called a seismograph.
The larger the number on the scale, the larger the earthquake.
You usually won’t even notice an earthquake unless it measures at least a 3 on the scale.
Here is what might happen at each stage of the scale:
4.0 – Could shake your house . Some people may not notice.
6.0 – Stuff will fall off of shelves. Walls in some houses may crack and windows break.
7.0 – Weaker buildings will collapse and cracks will occur in bridges and on the street.
8.0 – Many buildings and bridges will fall down. Large cracks will appear in the earth.
9.0 and up – Whole cities could be flattened and there will be alot of damage.

What are Seismic Waves?
Shock waves from an earthquake that travel through the ground are called seismic waves. They are most powerful at the center of the earthquake, but they travel through much of the earth and back to the surface. They move quickly at 20 times the speed of sound.

What is a fault line?
Earthquakes are formed along fault lines. This is an area of stress in the Earth. At fault lines the rocks are sliding past each other and will eventually cause a crack in the Earth’s surface.

Foreshocks and Aftershocks?
Before and after a large earthquake there will be smaller earthquakes. The ones that happen before are called foreshocks. The ones that happen after are called aftershocks.
What are the Epicentre and focus of Earthquakes?
The epicenter is the point on the Earth’s surface directly above where the rocks ruptured.
The focus of the earthquake is where the rocks actually ruptured. The focus is often miles beneath the Earth’s surface.

What do I do in an earthquake?
DURING AN EARTHQUAKE: DROP, COVER AND HOLD ON! Stay indoors until the shaking stops. Stay away from windows. If you’re in bed, hold on and stay there, protecting your head with a pillow. If you’re outdoors, find a clear spot away from buildings, trees and power lines. Then, drop to the ground. If you’re in a car, slow down and drive to a safe place. Stay in the car until the shaking stops.