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An Earthquake.... with shocking characteristics – teacher’s sheet
1 Yesterday, there was an earthquake
which was felt by millions of people
around the world. The focus of the
earthquake was deep under the
5 islands of the Carribean; however,
strangely enough, the tremors were
felt more strongly in other, faraway
places such as Australia and Canada
than in the islands directly above the
10 point from which the shockwaves
originated.
Scientists
in
seismological
laboratories around the world are
already analysing information that
15 has been recorded by sensitive
tremor-detecting equipment. There
are many peculiar and surprising
things about this odd and
unexpected seismic event:
20 First, the strange distribution around
the world of the strength with which
the shockwaves have been felt on
the surface of the Earth; most of the
energy (approximately 70%) released
25 from
the
rock-fracture
was
transported by the shockwaves at a
depth below ground-level at which
normally only 15% of the total
energy released is transported.
30 Secondly, the orientation of the the
fault plane along which the fracture
in the rock occured has been shown
to be horizontal – normally the
fracture plane of an earthquake is
35 inclined at between twenty and
eighty-five percent.
Also, the focus of the earthquake
was unusually deep - approximately
320 kilometres below the Carribean
40 Sea, some 60 kilometres North of
the Los Roques archipelago, owned
by Venezuela. This factor disproves
the theory, that was until now
widely accepted, that directly
45 beneath the Earth’s crust, which has
a maximum thickness of 50
kilometres is a layer of molten rock,
500 to 600 kilometres thick, since
when an earthquake occurs, it is
50 caused by a sudden fracture in the
rock at the focus of the earthquake,
and hence, the rock at that point
must clearly be solid.
The Task:
Students must work out by inference the
words that have been chopped off the
end of each line in the text.
Earth’s surface
X
*
X
Fault plane
*
* Maximum amount of energy
transported in these directions.
X - Focus of the earthquake
The diagram above shows the directions in
which pressure is exerted in relation to the
fault plane. Parts of the ground on opposite
sides of the fault plane experience forces in
the opposite direction to each other, as
shown by the differently shaded parts of the
diagram.
An Earthquake.... with shocking characteristics – students’ sheet
1 Yesterday, there was an earthquake
which was felt by millions of people
around the world. The focus of the
earthquake was deep under the
5 islands of the Carribean; however,
strangely enough, the tremors were
felt more strongly in other, faraway
places such as Australia and Canada
than in the islands directly above the
10 point from which the shockwaves
originated.
Scientists
in
seismological
laboratories around the world are
already analysing information that
15 has been recorded by sensitive
tremor-detecting equipment. There
are many peculiar and surprising
things about this odd and
unexpected seismic event:
20 First, the strange distribution around
the world of the strength with which
the shockwaves have been felt on
the surface of the Earth; most of the
energy (approximately 70%) released
25 from
the
rock-fracture
was
transported by the shockwaves at a
depth below ground-level at which
normally only 15% of the total
energy released is transported.
30 Secondly, the orientation of the the
fault plane along which the fracture
in the rock occured has been shown
to be horizontal – normally the
fracture plane of an earthquake is
35 inclined at between twenty and
eighty-five percent.
Also, the focus of the earthquake
was unusually deep - approximately
320 kilometres below the Carribean
40 Sea, some 60 kilometres North of
the Los Roques archipelago, owned
by Venezuela. This factor disproves
the theory, that was until now
widely accepted, that directly
45 beneath the Earth’s crust, which has
a maximum thickness of 50
kilometres is a layer of molten rock,
500 to 600 kilometres thick, since
when an earthquake occurs, it is
50 caused by a sudden fracture in the
rock at the focus of the earthquake,
and hence, the rock at that point
must clearly be solid.
Earth’s surface
X
*
X
Fault plane
*
* Maximum amount of energy
transported in these directions.
X - Focus of the earthquake
Edge of the column