Download 06 Volcanoes and earthquakes

Unit 6
VOLCANOES AND EARTHQUAKES
LEARNING AIMS
After this unit, you should be able to:
• actively use key terminology connected with volcanoes and
• explain the nature, causes and effects of earthquakes and volcanic activity
• understand the hazards and benefits of volcanoes
KEY WORDS
ash, avalanche, cone, core, crater, crust, crustal plate, earthquake, epicentre, erupt, eruption, fault, focus,
geothermal energy, lahar, lava, magma, magma chamber, magniture, mantle, molten, melted, tectonic plate,
seismograph, seismologist, seismic wave, vent, viscous, volcanic, volcano, volcanologist
LEAD-IN
A Work with a partner and discuss these questions.
1 Would you rather live in an area where a volcano eruption or an earthquake might occur? Why?
2 Why do you think the effects of volcanoes and earthquakes are more severe and long-lasting
in less economically developed countries than in more economically developed ones?
Discuss how authorities in these countries might respond to help people prior to, during
and after a disaster.
3 Can you think of some examples of how people might benefit from volcanic activity? Consider
agriculture, building materials and tourism in your answer.
B Here is a list of six places where major volcanic eruptions or earthquakes have happened since 1980.
Where did the earthquakes occur? Can you add at least two more earthquakes and eruptions to the list?
Mt St Helens, north-west USA (1980)
Mauna Loa, Hawaii, USA (1984)
Mexico City, Mexico (1985)
San Francisco, California, USA (1989)
Kobe, Japan (1995)
Montserrat, Caribbean (1995-1997)
C Earthquakes and volcanic eruptions occur along the edges of massive slabs of rock called tectonic plates
which are always moving, sometimes coliding with each other and causing the disasters. In pairs, complete
the answers below using the clues in brackets.
1 What is the name of the theory which explains
how tectonic plates move?
___________________ TECTONICS
(You eat food from it.)
2 According to this theory, there are two types of
plates. Which ones?
OCEANIC AND __________________
(What is Europe, Asia, etc.? Use the adjective.)
3 The area of frequent earthquake and volcanic
activity around the Pacific Ocean coincides with the
boundaries of some main tectonic plates. What is it
called?
THE PACIFIC ___________________ OF FIRE
(You wear it on your finger.)
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Unit 6
EX 1 READING AND VOCABULARY Work in two groups.
Group A Read and listen to the text about volcanoes.
Group B Read and listen to the text about earthquakes.
many active volcanoes are located near areas of dense
VOLCANOES (CD 6.1)
population.
A typical volcano is a mountain made from lava (molten
A volcanic eruptions can cause death and destruction
surface rock) and ash. An active volcano may erupt at any
through either a lava flow or a mudflow called lahar (a
time. There are about 500 such volcanoes in the world,
mixture of water, ash and rock turned to mud), or a dust
although only 20 or 30 erupt each year.
and ash cloud, which causes gloomy days as it shuts down
Not all volcanoes
the sun and can completely bury buildings and crops, or a
are alike or erupt in
nuée ardente, (a cloud formed by hot ash and poisonous
the same way. Most
gases which moves very fast and kills anyone breathing it
volcanoes are of the
almost instantly). Sometimes eruptions under the ocean or
composite type. They
on volcanic islands can produce tidal waves called
are roughly cone
tsunamis a long way from the original site. These huge
shaped with a large
waves usually have very devastating effects. One of the
hollow, which is
most cited cases is the eruption of Krakatoa in 1883.
called a crater, at the
When the volcanic island exploded, over 36,000 people
top of the cone. A
were swept to their deaths along the coasts of Java and
few volcanoes are
Sumatra by waves up to 35 metres high. 300 towns and
made almost entirely
villages were destroyed.
of lava. When a
Scientists try to predict eruptions by taking
volcano
erupts,
measurements of events leading up to possible activity,
magma (molten underground rock) pushes from its
such as earthquakes, ground movement, and the release of
chamber towards the surface. Clouds of ash and steam as
gases. Despite several encouraging successes, including
well as lava come out of the hole or vent in the crater
the 1991 eruption of Mount Pinatubo, Philippines, and
through the pipe. The lava builds up in layers so that the
several recent eruptions of Sakurajima Volcano in Japan,
volcano grows larger with each eruption. A volcanic
the biggest obstacle to improving eruption prediction is
eruption can last for as little as an hour or for more than
that only a tiny fraction of over 500 active volcanoes in
a year. During the eruption the volcano is active, but it
the world are adequately monitored by modern
then becomes dormant (not active at present) until the
instruments and well-trained volcanologists (people who
next period of activity. During the quiet period, the lava
study volcano formations and eruptions). Although
in the crater solidifies, plugging the vent. Gas pressure
volcanic eruptions cannot be prevented, some measures
builds up inside the volcano until a new vent opens up
can be taken to reduce their effects. For example, lava
and another eruption begins. This may happen with a
flows can be diverted from vulnerable areas or halted by
sudden explosion if the lava is viscous (thick
and pasty)
water sprays. The most sensible precaution against a
(
and holds a lot of gas. If a volcano has not been active for
volcanic eruption is to evacuate everyone living near an
many centuries, it is labeled extinct (no longer active) –
active volcano and to prepare these people for it by
though supposedly extinct volcanoes have come to life
organizing evacuation procedures prior to the disaster.
again. Helgafell volcano in Iceland had been dormant for
However, most people are unaware of the fact that
more than 5000 years when it erupted in 1973.
volcanic areas can be very beneficial to humans. Volcanic
Volcanoes are generally found in narrow belts either
ash weathers to produce very fertile soils, excellent to
in the ocean or on land, usually close to where plate
intensive farming, e.g. lower slopes of Mt Etna, Sicily.
boundaries (plates are parts of the crust, the outer surface
People in Iceland use geothermal energy (energy from
of the Earth) pull apart or are coming together. In
volcanic water and steam) to supply heat and electricity.
contrast to earthquakes, they are usually not created
In addition, volcanic rock makes good building stone.
where two tectonic plates also slide past one another.
Finally, volcanoes attract adventurous tourists to visit
Some volcanoes are located in remote parts of the world,
some volcanic sites, such as those in Iceland, New
so the eruption may hardly be noticed, as in the 1912
Zealand or southern Italy (Vesuvius and Stromboli).
eruption of Mount Katmai in Alaska. Unfortunately,
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Unit 6
EARTHQUAKES (CD 6.2)
An earthquake is a sudden, sometimes violent, shaking of
the ground caused by the sudden release of stored energy
within the Earth’s crust. Earthquakes are natural events,
like snowstorms or tornadoes, and more than 150,000 of
them happen every year. Most earthquakes are so small
that they cannot be felt by humans, though they can be
detected by sensitive instruments called seismographs
which measure earthquake strength or magnitude on the
Richter Scale. Numbers on this scale range from 0 to 9,
though no real upper limit exists. An earthquake whose
magnitude is greater than 4.5 on this scale can cause
damage to buildings and other structures. Major
earthquakes have magnitudes greater than 7 and release
huge amounts of energy, equivalent to a large nuclear
explosion, within a few minutes.
Although the Earth feels solid and unmoving to us,
that isn’t really the case. The planet surface is actually
made up of seven large, and several smaller, crustal plates
moving in continual motion over the planet’s molten core.
Compression forces continually create stress on the rock
within and between each of these plates. When the rock
can no longer withstand the stress they suddenly break or
slide creating what we feel as an earthquake. This sliding
or fracture in the crust called a fault and the resulting
movement of the Earth’s plates produce shock waves
called seismic waves. They spread out in all directions
from the focus and cause an earthquake. After a major
earthquake, there can be one or more aftershocks
through the middle of the Atlantic Ocean for its entire
length. A third belt stretches across the continents of
Europe and Asia from the Atlantic to the Pacific. There
are other short belts, including one going westwards from
the West coast of South America. Volcanoes, which often
set off earthquakes, also appear in long narrow belts and
their distribution around the world is very similar to that
of earthquakes.
Severe earthquakes occur in some of the most denselypopulated parts of the world, such as Japan and China.
Collapsing buildings and bridges account for most loss of
life during earthquakes. People may be trapped beneath
piles of rubble or killed by flying debris (the scattered
remains of something broken or destroyed) in the street.
Hospitals may also be hit, so people in less developed
countries may sometimes die from exposure to the
weather, from lack of food and water, or from disease.
Fallen bridges, twisted rail tracks, damaged roads and
airfields all slow down the arrival of help from outside.
In cities, fire often breaks out when gas and oil pipes
break under the strain. In mountainous areas,
earthquakes often trigger an avalanche (a slide or fall of a
large mass of snow, ice and rock). If the earthquake is
created by sudden movements of the plates on the ocean
floor, it can also trigger tsunamis.
Despite much research, it is only possible to predict
where earthquakes are likely to occur but not when. The
signs that help to warn people and which are currently
investigated by seismologists (geophysicists who study
earthquakes and related phenomena) include: evidence
from past earthquakes, unusual animal behaviour or gas
emission from the ground. Early warnings of earthquakes
could save thousands of lives. However, when millions of
people have to be evacuated, false alarms can be very
costly.
EX 2 SPEAKING Answer these questions about
volcanoes or earthquakes with your group.
(earthquakes of smaller magnitude) in the same area.
They occur as the displaced plate boundary tries to adjust
itself. The place where the earthquake originates is called
its focus. Shock waves spread out from the focus in
all directions, like ripples on the pool’s surface, but the
maximum destruction of lives and property usually occurs
at the epicentre, which is on the surface directly above
the focus. The amount of damage usually decreases with
distance from the epicentre.
Earthquakes occur in long narrow belts. The largest
belt is the one which goes around the entire Pacific
Ocean. The second most obvious is the one which runs
1 What is a volcano or an earthquake? Can you
describe their meain features?
2 What causes them?
3 Are volcanoes or earthquakes measured? How?
4 Can volcanoes or earthquakes occur more than
once in the same area?
5 Is there a specific pattern to their distibution
around the world?
6 Why do they pose such a great threat to people
and their surroundings?
7 Is it possible to predict or prevent them?
8 Are there any benefits from volcanoes or
earthquakes?
PP
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VOLCANOES AND EARTHQUAKES
Unit 6
EX 3 Which of the following numbers relate to your topic? What do they refer to?
4.5
500
150,000 35 5000
7
EX 4 What do the highlighted words in your text mean? Write a sentence about each term and compare the
information in pairs. Use the text to help you.
EX 5 ROLE-PLAYING Work with a partner from the other group.
Student A is a volcanologist or a seismologist.
Student B is a geography student doing a project on volcanoes or earthquakes.
Ask and answer ten questions about volcanoes or earthquakes, using the questions
in exercise 2 and your own questions. Swap roles.
EX 6 When you have finished, do the quiz on p. 33.
EX 7 LISTENING (CD 6.3) Listen to Andrea Matta, a girl from Brazil, who has lived through an earthquake
in California. First, try to put the main events of her story in the correct order. Then listen and check.
1 When the aftershocks ended, Andrea tried to call her parents in Brazil.
2 Outside in the street, somebody told them that the epicentre was not far away.
3 After that they went into the street.
4 They waited in her friend’s room until the earthquake stopped.
5 She started to cry and her friend tried to calm her down.
6 Andrea’s friend woke her up by shouting “It’s an earthquake! Get up!”
7 She was finally able to talk to her family on the phone.
8 As they were leaving, they saw how badly their building had been damaged.
9 Then the flat started shaking again.
10 When it was over, they noticed that most things around them had broken.
EX 8 DISCUSSION Listen again. Then work with a partner and discuss these questions.
1
2
3
4
How did Andrea feel during the earthquake?
Why couldn’t she call her family at first?
What damage did the earthquake cause to the buildings in the street?
Which American English words does Andrea use instead the British English words
‘flat’ and ‘video recorder’?
5 If you were Andrea, would you go into the street after the earthquake too? Why (not)?
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