Living on plate boundaries - earthquakes - Mrs G

Living on plate boundaries - earthquakes - Mrs G

Multiple Select

What happens at a constructive plate boundary?

• tectonic plates move alongside each other

• tectonic plates move apart

• one tectonic plate is subducted under the other

• tectonic plates sink

Multiple Select

Which type of volcano is associated with destructive plate boundaries?

• shield volcano

• cinder cone

• composite volcano

Multiple Select

What happens at a destructive plate boundary?

• tectonic plates move apart

• one tectonic plate is subducted under another plate

• tectonic plates move alongside each other

• tectonic plates float

Multiple Select

Which continent is South America slowly floating away from?

• Europe

• Asia

• Africa

• Antarctica

Multiple Select

What is the correct name for molten rock found in the mantle

• lava

• basalt

• pumice

• magma

Multiple Select

Which is the thickest layer of the earth?

• crust

• mantle

• outer core

• inner core

Learning Intentions

- To describe how earthquakes happen.

- To understand the effects these have on people 

Earthquakes occur at destructive and conservative plate boundaries

Which diagram shows a destructive plate boundary?

Which diagram shows a conservative plate boundary?

Destructive margins

Pressure builds as the two plates move against each other

As pressure is released suddenly, earthquakes occur

Conservative margins

Earthquakes occur here when two tectonic plates slide past each other and get stuck. This builds pressure which is suddenly released as seismic waves at the focus.

These waves cause the ground to move in different ways. We see the ground move in waves spreading from the epicentre of the quake

Chile video

Watch the video and write down as many effects as you can on your pad or in the chat stream

Measuring the severity of earthquakes

It is important to measure the severity of an earthquake so that governments know what level of support is needed to help people affected by the quake.

There are two main ways that we can measure how severe an earthquake is....

1. The Richter Scale

The Richter Scale measures how much energy is released in an earthquake. It measures this on a scale of 0 to 9 where each level has 10 times as much ‘ground shaking’ as the one before.

When we hear about earthquakes in the news, they usually give its strength using the Richter Scale from 1 to 9

What are the positives and negatives of using the Richter scale?

It is quite easy to measure and the equipment isn’t very expensive, so everyone in the world can afford to use one. It is calculated by a machine, so it is quite accurate. 

It works best for earthquakes that are small- to medium-sized – and it can give slightly wrong readings for really bad earthquakes. 

2. The Mercalli Scale

This scale measures how much destruction has been caused by an earthquake based on what you can see.

It uses numbers (written in Roman Numerals) on a scale of I (1) to XII (12).

Can you suggest some of the positives and negatives of using this scale to describe earthquake damage?

Mercalli Scale

You decide on how severe an earthquake is based on the effects that people experience and see.

Mercalli scale - positives and negatives

• +ve - it is quite easy to measure and doesn’t use any equipment, so it’s easy to get an idea of the level of destruction. 

• -ve - it is a personal opinion, so its not so accurate - one person might feel the earthquake a bit more than someone else than someone else

• -ve - it is unlikely that all the buildings affected by an earthquake are damaged in exactly the same way so it may not give an accurate picture of the damage

How bad is an earthquake - using the Mercalli Scale

Review the pictures and rank them in order from the least serious damage to the most serious damage

Mercalli Scale

Now for each picture give them a score on the Mercalli scale

Describe some of the damage that you can see

Can you justify your choice of score?

Categorising the effects of earthquakes

• The effects of an earthquake can be divided into primary and secondary effects

• Primary effects are those which are immediate and predictable

• Secondary effects are those which result or follow on from the primary effects

• Rewatch the video of the Chile earthquake

• Can you identify at least two primary effects and one secondary effect. Write them in the chat stream

Chile video reshow

Multiple Select

What causes earthquakes at destructive plates

• Friction between the oceanic and continental plate

• Gases in the magma

• Melting rock as the oceanic plate moves under the continental plate

Multiple Select

What happens at a conservative plate boundary?

• tectonic plates move together

• tectonic plates move apart

• tectonic plates move alongside each other

• tectonic plates sink

Multiple Select

How does the Richter scale measure earthquakes?

• It uses a visual interpretation of the damage caused by the earthquake

• It considers how far tectonic plates have moved

• It measures the strength of the earth's shaking during the earthquake

Open Ended

Write down one positive reason for using the Mercalli scale

Open Ended

Write down one reason why using the Mercalli scale might not be helpful

Multiple Select

Which of the following impacts are primary effects

• people die

• people lose their jobs

• people become homeless

• water and gas pipes are broken

Open Ended

Explain why homelessness can be described as a secondary effect of an earthquake

Open Ended

Do you think the effects of earthquakes or volcanoes are more severe?

Write a paragraph to give your opinion.