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NORWOOD SCIENCE CENTER
Geology
Grade 4
Background information:
The movement of crustal plates provides the great forces that
strain the Earth's crust causing earthquakes to occur. Probably no
other natural event has been the cause of more deaths and
destruction than earthquakes. Modern technology has given the
scientists tools to study these events in detail. The theory of plate
tectonics has provided scientists with the ability to explain why they
occur.
There is hardly a region on Earth where an earthquake will not
occur, given sufficient time. Most serious earthquakes occur where
the crustal plates come together. The boundaries between the plates
are actually huge cracks in the crust. As the plates slowly move, their
edges grind together. The plates move against each other along
these cracks in crustal rocks. A place where the rock has moved on
one or both sides of a crack is called a fault.
Almost all large earthquakes take place when rocks suddenly
snap along faults. If the rocks along a fault were constantly moving,
their surfaces would soon be worn smooth. The rocks would slide
gently like a well-oiled drawer. However, the rock surfaces are
jagged. The sides of a fault area usually are locked together like a
Earthquakes Gr. 4
© The Norwood Science Center 2005
sticky drawer. This causes stress. When the stress becomes too
great, the rocks suddenly snap and slip along the fault. This
movement causes a sudden release of the built-up stress causing an
earthquake.
There are a number of places in the world where earthquakes
occur frequently. In this lesson, students will explore where
earthquakes most often occur and find that they are related to crustal
plate boundaries.
Earthquakes Gr. 4
© The Norwood Science Center 2005
TITLE:
EARTHQUAKES
PURPOSE:
Can you predict earthquake locations?
MATERIALS:
(per teacher)
One crustal plate map of world with plate numbers
Overhead of crustal plate map
Overhead markers
(per student)
One crustal plate map of the world with numbers
One earthquake coordinate worksheet
Pencil
PROCEDURE:
Advanced preparation:
01. Teacher should prepare an overhead of the crustal plate map.
Classroom lesson:
02. Pair students into teams.
03.
Distribute one crustal plate map to each student.
04.
Using the overhead, have students write the names of the
seven major crustal plates of the Earth’s crust in the lower
margin of their map:
•
#1 – Pacific Plate (on both sides of the map)
•
#2 – North American Plate
•
#3 – South American Plate
•
#4 – Antarctic Plate
•
#5 – African Plate
•
#6 – Eurasian Plate
•
#7 – Indian-Australian Plate
Discuss with students that the areas on the map indicated with
the jagged bold lines are the boundaries between these major
crustal plates.
05.
Earthquakes Gr. 4
© The Norwood Science Center 2005
07.
Most serious earthquakes occur where the crustal plates come
together. The boundaries between the plates are actually huge
cracks in the crust. As the plates slowly move, their edges
grind together. The plates move against each other along
these cracks in crustal rocks. A place where the rock has
moved on one or both sides of a crack is called a fault.
08.
Distribute one earthquake coordinate worksheet to each
student. Explain to the class that the coordinates given were
derived from actual earthquake activity that occurred during
those time periods.
09.
Guide students in locating the first two positions where
earthquakes occurred.
10.
Discuss with students that magnitude indicates the power of an
earthquake as measured on the Richter Scale. The scale uses
numbers to show the amount of energy released by an
earthquake. Each number on the scale represents ten times as
much energy as the next lower number. For example, an
earthquake with a magnitude of 5 is ten times stronger than an
earthquake with a magnitude of 4. Most earthquakes are small
with Richter measurements of four or less. Large earthquakes
with values of eight or more usually take place only once every
five to ten years.
11.
Student teams should complete locating all earthquakes.
Earthquakes Gr. 4
© The Norwood Science Center 2005
CONCLUSION:
After locating all the earthquakes, have students answer the following
questions:
01.
Describe where the earthquakes are located.
02.
Is there a relationship between the earthquake positions and
the shape of the continents?
03.
Describer how the locations of the earthquakes are related to
crustal plate boundaries.
04.
Complete the following sentence: The pattern we found for
earthquake locations suggests that future earthquakes may
occur …
SOURCE:
01.
Earth Science. Holt, Rinehart and Winston, New York, 1986.
Earthquakes Gr. 4