The earth and how it moves

This is a theory that the earth’s crust is made up of several “plates” that move past one another.

It has been suggested that at some point all of these plates were all together in one massive continent called Pangea

200 Million Years Ago

135 Million Years Ago

65 Million Years Ago

Present Day

There are different types of boundaries that occur between plates

Constructive boundaries:Mid Ocean Ridges were ocean crust is made

Destructive boundaries:Subduction zones where ocean crust is pushed bellow continental crust and melts

Movements in the earth’s crust that can cause huge amounts of damage

But some may ask – Can they be prevented?

Earthquakes are measured on two different scales.

The Mercalli Scale – Measures the damage done at a particular location.

The Richter Scale – Measures the magnitude of the earthquake (how much energy is released) on a scale of 1 to 10.

A seismograph is an instrument which measures the movements of the ground.

It shows this movement on a continuous zig-zag line.

A seismograph will show 3 periods of shaking. One for the arrival of each type of wave.

September 1985Mexico City

8.1Killed 7000

1964Alaska

9.2Killed 131

October 1989San Fransisco

7.1Killed 62

January 1995Japan

7.2Killed 6400

3 different waves move through rock like ripples in a pond.

P-Waves or primary waves are the first waves to hit as they move the fastest (8km/s). They squeeze and stretch the rock.

The next waves to hit are the secondary waves (S-Waves). These waves move at 5km/s and make the ground shake up and down as well as from side to side.

Traveling at 4km/s are the last waves to hit, the L-Waves. These waves do the most damage as they travel near the surface of the crust.

All three together.

Do you think they can be prevented?