Why does the Earth quake?

 The Surface of the Earth is like a massive jigsaw puzzle made up of huge rocky pieces called tectonic plates. The pieces of this puzzle are constantly moving about very slowly, but with immense force. If they slide past or crash into each other the Earth shakes and quakes.

Five Famous Earthquakes:

• 1755 Lisbon, Portugal: one of the worst earthquakes in history was followed by tsunami and many fires.
• 1906 San Francisco, USA: Fires following this massive quake left 3,000 dead and 20,000 homeless.
• 1964 Alaska, USA: This powerful quake lasted nearly five minutes and was followed by tsunami.
• 1995 Kobe, Japan: Lasting barely 20 seconds, this quake killed 6,400 people and caused US$200 billion in damage
• 2003 Bam, Iran: The City many mud-brick buildings were destroyed by this massive earthquake.

The Richter Scale

Magnitude	Description	Effects
Less than 2	Micro	Not felt
2-2.9	Minor	Generally not felt, but recorded
3-3.9	Minor	Often felt but damage rare
4-4.9	Light	Noticeable shaking of indoor items, rattling noises
5-5.9	Moderate	Can cause damage to poorly constructed buildings over small areas. At most, slight damage to well- designed buildings
6-6.9	Strong	Can be destructive in areas up to 160 km across
7-7.9	Major	Can cause damage over large scale
8-8.9	Great	Can cause serious damage in areas several kilometres across
9-9.9	Great	Divasting in areas several thousand kilometres across
10+	Epic	Never recorded

Quake Measures 

Scientists measures earthquakes in two different ways - by its magnitude or its intensity. 

Magnitude means the power of the shock waves and its usually measured on the Richter scale. The Modified Mercalli Intensity scale measures the effects of an earthquakes.