Lesson 39:
Physical Features of the Pacific Region
Along theWest Coast isahiddenphysical feature that causesagreat deal of concern for thepeo-
ple who live there. Beneath the earth’s crust are huge layers of rock that scientists call
plates
.
Scientists tell us that more than a dozen plates cover the earth’s surface. The movement of these
plates is very slow, just a few inches a year.As these plates very slowly push, pull, and collide togeth-
er, fractures in the earth’s surface can also occur.These fractures, or breaks, are called
faults
. It is at
theseweak points, or faults, in the earth’s surface that earthquakes and volcanoes take place.
Following the line of the Coast Ranges in California, Oregon, and Washington are the North
American andPacificPlates.Where these platesmeet underground is called the
SanAndreasFault
.
ACTIVITY 1:
Using the regional map of the Pacific Region on the next page, locate the dotted line in Southern
California labeled
SA
. Follow this line northward along theWest Coast to San Francisco using a red
pencil.You havemarked the
SanAndreas Fault
. Along this fault line a number of earthquakes have
been recorded.
This dotted line alsomarks the area known as the
Ring of Fire.
The Ring of Fire is a band that
surrounds or encirclesmuchof thePacificOcean.Many of theearth’s active volcanoes are locatedon
the Ring of Fire. Continue to follow the dotted line with your red pencil along the coast of the North
AmericanContinent to Alaska and the Aleutian Islands.TheRing of Fire follows the dotted line to the
Aleutian Islands and continueswest towardAsia.Earthquakes and even volcanic activity, such as the
eruptionofMount St.Helens in the stateofWashington in1980, haveoccurredalong thisRingof Fire.”
Later this year you will learn that the Ring of Fire also affects the people living on the west coast of
Central America andSouthAmerica.
Hawaii
is greatly influenced by volcanic activity. Each of the present 132 islands has been creat-
ed by volcanic activity. The islands are actually tops of giant ocean volcanoes. Some islands have
beaches with fine black sand made of volcanic glass that has been crumbled and smoothed by the
ocean’swaves.Scientists have even discovered a new island being formed underwater.As thePacific
Plate slides over ahot spot under theearth’s surface, it causes a landmass to rise.Although this land-
mass is presently 3,000 feet below the ocean’s surface, someday it will become a new island in
Hawaii’s chain.
ACTIVITY 2:
Match each word inColumn Bwith its proper description in Column A by writing the number in the
appropriate blank space.
Note: There is aword or phrase inColumnB that will not be used.
ColumnA
layers of rock under the earth’s surface
a fracture linewhere theNorthAmerican andPacific Plate collides
a line of volcanoes that encirclemuch of thePacificOcean
landforms created by volcanic activity
breaks in the earth’s surfacewhere earthquakes
and volcanoes take place
COPYRIGHT
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PENNSVALLEY
Pacific Region
ColumnB
1. faults
2.Ring of Fire
3.Mount St. Helens
4. plates
5. SanAndreas Fault
6.Hawaiian Islands
