Key Questions:

How do earthquakes happen?

How are they measured?

Learning Objective:

To learn to ask geographical questions.To recall knowledge as to how earthquakes happen.To know how earthquakes are measured.

Starter

Look carefully at the next photograph.

On post-it notes cover your copy with relevant geographical questions you would ask to find out what happened.

What are earthquakes and where do they occur?

Earthquakes are vibrations caused by earth movements at plate boundaries and at major fault lines (cracks in the earth’s surface).

They can occur at all 4 major plate boundaries but the most severe earthquakes are normally found at CONSERVATIVE and DESTRUCTIVE boundaries.

CONSERVATIVE

DESTRUCTIVE

How can we measure earthquakes?

The largest earthquake ever recorded was in Chile. It measured 8.9 on the Richter Scale.

This measures the magnitude of a tremor (how powerful it is) using an instrument called a seismograph.

On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions. Although the Richter Scale has no upper limit, the largest known shocks have had magnitudes in the 8.8 to 8.9 range. It is a logarithmic scale which means that a size ‘6’ on the Richter Scale is 10 times larger than a size ’5’ and 100 times larger than a size ‘4’.

1234

65

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Richter Scale

The Richter Scale

The Japanese earthquake in Kobe (September 1995) measured 7.2 on the Richter Scale.

The Greek earthquake (June 1995) measured 6.2 on the Richter Scale.

How many times greater was the Japanese earthquake?

How can we measure earthquakes?

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Richter Scale

Mercalli Scale

This measures how much damage is caused by the earthquake based on observations. It is measured on a scale between I and XII.

Mercalli Scale

Your task is to create a ‘living graph’ with the seismograph using the statements given.

True or False