2
40
2. Relief
5.2. Earthquakes
The majority of earthquakes are registered on the surface of the continents.
There are two main parts of an earthquake:
❚
The
hypocentre
is the point in the Earth’s interior where there is a great explosion
or rupture. Seismic waves originate from this point and travel to the surface.
❚
The
epicentre
is the point in the Earth’s surface directly above the hypocentre. This
is the area that is most affected by the seismic waves which cause the ground to
shake and the destruction of houses and other buildings. The closer an area is to
the epicentre, the greater the destruction will be.
The strength of an earthquake is measured on the Richter scale.
Earthquakes
are sudden movements of the Earth’s crust produced by a
release of
energy
from the Earth’s interior in the form of
seismic waves
.
When an earthquake is produced under the sea, it causes a
tidal wave
. When this
happens, the seismic waves are almost undetectable but can cause giant waves called
tsunamis
, which can reach up to 60 m (higher a 15-floor building). If a tsunami
reaches the coast, it can cause catastrophic damage.
INTENSITY OF
EARTHQUAKES
Magnitude
(Richter
scale)
Earthquake
effects
Less than
3.5
Not felt, but
registered on the
scale.
3.6-5.4
Effects felt and
causes minor
damage.
5.5-6.0
Causes damage to
buildings.
6.1-6.9
Car cause damage
in highly populated
areas.
7.0-7.9
A major
earthquake. Causes
severe damage.
8 or more
A very large
earthquake. Causes
destruction in
surrounding areas.
Understand
21.
Watch the clip from the
tsunami documentary
.
Describe the scene in your notebook.
22.
Look at the Richter scale table. Listen and say the
magnitude of the earthquakes described.
23.
Find out what the signs of an active volcano are.
What information indicates that a volcano is
active?
Evaluate
24.
Write an essay about the effect of the different
materials ejected by a volcano on inhabitants of an
area and the natural environment.
Create
25.
Ocean trenches are in the deepest part of the ocean
floor. Their enormous slopes are home to unique
habitats and species still unknown to science. Find
out about the deepest ocean trenches, where they
are and why they are important.
26.
Search the Internet for information about these
volcanoes: Mount Etna, Mt. Popocatépetl and
Mount Kilauea. Write a report about each one.
Include:
❚
Location (continent, country, region)
❚
Populated areas close to it
❚
History (the activity of the volcano and when)
❚
If there is present risk of volcanic activity
