Which is a reason people live near volcanoes?

fertile soil. Weathered volcanic rock is rich in minerals.

Which is a secondary impact of an earthquake?

fires from broken gas pipes. It is caused by damage done in the earthquake.

What does the Mercalli scale measure?

the intensity, from observed damage and effects. It runs from I to XII.

What does the volcanic explosivity index measure?

the size of an eruption. From 0 to 8, based on material ejected and the height of the ash column.

An earthquake of magnitude 7 has waves how many times larger than one of magnitude 6?

10 times. The scale is logarithmic.

The impacts of tectonic hazards · Cambridge IGCSE Geography (9

In plain words

Hundreds of millions of people live beside volcanoes and on top of faults. They are not foolish. For most of the time, these are good places to live, and for many there is no real choice.

8 things to know

Why people live in areas at risk: volcanic soils are very fertile; there is geothermal energy; volcanoes attract tourists; minerals are mined there; family, work and community are there; and many cannot afford to move.
Eruptions and large earthquakes are rare, so people judge the risk to be small, and trust warnings and buildings to protect them.
Primary impacts of an earthquake happen at once: buildings and bridges collapse, people are killed or injured, and water, gas and power lines are broken.
Secondary impacts follow: fires from broken gas pipes, tsunamis, landslides, disease from dirty water, homelessness, and the loss of jobs and trade.
Impacts of eruptions: deaths, destroyed homes and farmland, ash that grounds aircraft and ruins crops. In the long term, fertile soil and tourism.
The moment magnitude scale measures the energy an earthquake releases. It has replaced the Richter scale, which is based on the size of the waves on a seismograph. Both are logarithmic: each whole number is ten times the wave size of the one below.
The Mercalli scale measures intensity: the effects and damage observed, from I to XII.
The volcanic explosivity index (VEI) measures the size of an eruption from 0 to 8, by the volume of material thrown out and the height of the ash column.

Worked example

Explain why an earthquake of the same magnitude can kill far more people in one country than in another.

Building quality: where buildings are not designed to resist shaking, more collapse.
Preparation and response: wealthier countries have emergency services, hospitals and trained rescue teams ready.
Other factors: how deep the focus is, how many people live near the epicentre, and the time of day.

Tips and tricks

Primary impacts are caused directly by the shaking or the eruption. Secondary impacts are caused by the primary ones.
Magnitude measures energy and is one number for the whole earthquake. Intensity (Mercalli) measures damage and varies from place to place.

5 questions, about 2 minutes.

It lands in your notebook with its questions as flashcards.

The impacts of tectonic hazards: 5 questions and answers

These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.

Which is a reason people live near volcanoes?
- frequent eruptions
- fertile soil (the answer)
- cold climate
- lack of water
Weathered volcanic rock is rich in minerals.
Which is a secondary impact of an earthquake?
- buildings collapsing
- the ground shaking
- fires from broken gas pipes (the answer)
- roads cracking
It is caused by damage done in the earthquake.
What does the Mercalli scale measure?
- the energy released
- the intensity, from observed damage and effects (the answer)
- the depth of the focus
- the height of a tsunami
It runs from I to XII.
What does the volcanic explosivity index measure?
- the temperature of lava
- the size of an eruption (the answer)
- the age of a volcano
- the number of deaths
From 0 to 8, based on material ejected and the height of the ash column.
An earthquake of magnitude 7 has waves how many times larger than one of magnitude 6?
- 2 times
- 10 times (the answer)
- 7 times
- 100 times
The scale is logarithmic.

5 questions

Tap an answer and you’ll see straight away whether it’s right, and why.

Worksheet

3 questions, 9 marks. Write your answers on paper, then check them.

The impacts of tectonic hazards

Cambridge IGCSE Geography (9–1) 0976 · 9 marks · papermunch.org

Name ______________________________ Date ______________

Give three reasons why people live near volcanoes.[3]
Show answerHide answer
The soil is very fertile. There is geothermal energy. Tourists come to see volcanoes, which creates jobs. (Also: minerals, family ties, lack of money to move.)
I got this one
Describe two primary and two secondary impacts of an earthquake.[4]
Show answerHide answer
Primary: buildings collapse; people are killed and injured. Secondary: fires start from broken gas pipes; diseases spread because water supplies are contaminated.
I got this one
Describe the difference between the moment magnitude scale and the Mercalli scale.[2]
Show answerHide answer
The moment magnitude scale measures the energy released by an earthquake. The Mercalli scale measures its intensity, from the damage and effects observed.
I got this one

Answers: The impacts of tectonic hazards

1. The soil is very fertile. There is geothermal energy. Tourists come to see volcanoes, which creates jobs. (Also: minerals, family ties, lack of money to move.)
2. Primary: buildings collapse; people are killed and injured. Secondary: fires start from broken gas pipes; diseases spread because water supplies are contaminated.
3. The moment magnitude scale measures the energy released by an earthquake. The Mercalli scale measures its intensity, from the damage and effects observed.