Transcript EARTHQUAKES and KILLER WAVES

An earthquake sends shock waves rippling
through the ground.
Scientists study these waves to see how big
earthquake is. They measure earthquakes on a
scale of 1 to 10. Each quake on the scale is 30
times worse than the one before
Tectonic plates
What makes an
earthquake happen?
Planet Earth is
covered with a thick
crust. The crust is
cracked into more
than twenty sections
– a bit like the shell of
a boiled egg when
you tap it with a
spoon.
Tectonic plates
Earthquakes
happen all the
time in all parts of
the world but we
don’t notice them
because they are
small.
These cracked
sections are called
tectonic plates and
they are always on
the move. They move
very slowly, but with
incredible power.
When the plates rub
against each other or
collide with each
other, an earthquake
happens.
NO PROTECTION
• Nowadays, new
buildings in
earthquake-prone
towns and cities are
built to withstand
the shock of an
earthquake.
• Even so, during
seismic activity, gas
pipes and electricity
cables are ripped
apart and cause
fires and explosions,
so even if buildings
don’t fall down, there
can still be a lot of
destruction.
NO PROTECTION
San Francisco sits on
one of the greatest
earthquake zones in
the world. Children
have earthquake drills
at school, but,
unsurprisingly, people
hope that it will never
happen and are still
building new houses,
shops and office
blocks.
TSUNAMI
• A tsunami is a chain of
huge waves, again
caused by an
earthquake, but this time
under the seabed.
• Tsunami waves can be
very long (as much as
100km) and there may
be an hour between
them.
TSUNAMI
• They can move very
fast, too, sometimes
at the speed of 800
kilometres an hour.
• When a tsunami
reaches the
coastline, it slows
down but its height
grows. There have
been tsunami as
high as 30 metres
above the sea level!
TSUNAMI
The Christmas weekend
tsunami of 2004 is
probably the most
destructive one in the
history. It was caused by
an earthquake in the
Indian ocean measuring
9.0 on the Richter scale.
The huge waves crashed
into several Asian
countries and thousands
of people lost their lives.
Sounding the Alarm
• Before the huge waves of
the recent tsunami crashed
into the coastline areas, wild
and domestic animals
showed very unusual
behaviour.They seemed to
know what was going to
happen.
These clever animals not only
sensed the tsunami but saved • Do animals have a sixth
many people. As they ran off
sense? Can they predict
the beach, they lifted tourists
disasters? And why don’t
onto their backs with their
people learn to use these
trunks, taking them to a safe
place.
animal instincts?
Sounding the Alarm
According to eyewitness stories, the
following events happened:
• Elephants screamed and ran for higher
ground.
• Dogs refused to go outdoors.
• Zoo animals rushed into their shelters and
nothing could make them come out.
Sounding the Alarm

Such stories aren’t new. In 373 BC, historians
wrote that animals, including rats and snakes,
deserted the Greek city of Helice just days
before a quake destroyed the place.
 During the more recent earthquake in Turkey
in 1999, dogs howled like wolves for two days
before earthquake struck. No one took any
notice and many buildings fell down like stacks
of cards, killing over 17,000 people