PLATE PUZZLES
EQ – 03 & 04
MATERIALS:
• PLATE PUZZLE RUG OR a large WOODEN PUZZLE MAP
• PLATE NAME CARDS & ARROWS
• SEA FLOOR BASALT ROCK SAMPLE
•CALIFORNIA RELIEF and/or FAULT MAP
• PHOTOS SHOWING VARIOUS SITES OF FAULT ACTION
© Environmental Volunteers
Earthquakes
Plate Puzzles
EQ – 03 & 04
page 1
PLATE PUZZLES
EQ – 03 & 04
OBJECTIVES:
To better understand plate movements and their effects, either a wooden puzzle map cut into
the major earth plates or a large puzzle rug can be used. The connections between different
plates and plate boundaries can be easily seen by studying and moving the pieces of the PLATE
PUZZLES
SCIENCE THEMES:
Energy, Stability, Patterns of Change, Systems and Interactions
PROCESS SKILLS:
Observing, Ordering, Categorizing, Relating
GRADE LEVELS:
4—8
FOCUS WORDS:
Tectonics, plates, sea floor spreading, subduction, collision, thrust and transform faults
The earth's crust is divided into a number of moving plates that fit together like a jigsaw
puzzle. Although the boundaries of some of the plates remain uncertain, and the existence of
smaller plates within plates (jokingly referred to as "Flake tectonics") is most likely, geologists
commonly refer to the following 12 major plates:
1.
PACIFIC PLATE
2.
NORTH AMERICAN PLATE
3.
COCOS PLATE
4.
CARIBBEAN PLATE
5.
NAZCA PLATE
6
SOUTH AMERICAN PLATE
7.
AFRICAN PLATE
8.
ARABIAN PLATE
9.
EURASIAN PLATE
10.
INDIAN-AUSTRALIAN PLATE
11.
PHILIPPINE PLATE
12.
ANTARCTIC PLATE
Other minor plates that have been indicated by geologists are: Iran Plate, Caroline Plate,
Bismarck Plate, Solomon's Plate, Gorda Plate, Scotia Plate, Juan de Fuca plate, Farallones Plate
and others.
© Environmental Volunteers
Earthquakes
Plate Puzzles
EQ – 03 & 04
page 2
BACKGROUND INFORMATION:
The plate boundary around the Pacific Ocean is called the "Ring of Fire" because of the
particularly heavy concentration of earthquakes (80% of the worlds quakes!) and volcanoes
(95%!) along this belt. A portion of the "Ring" cuts through the length of California, separating
the Pacific Plate from the North American Plate in a boundary known as the San Andreas Fault.
Along the San Andreas Fault, the Pacific Plate moves northwesterly in relation to the North
American Plate (which is also moving) an average of 2 inches a year, or about as fast as
fingernails grow. In some places the rocks along the fault zone are "locked," while in others the
rocks are “creeping." When the plates unlock, or move suddenly, another earthquake occurs.
Today we know that both the ocean floor and the continental masses ride along on the backs of
giant, moving plate crusts. The existing boundaries of the earth's plate crusts are dramatically
outlined by global bands of earthquake activity and volcanoes. Scientists have created graphic
simulations of the entire history of plate movement based on a wealth of geological findings.
Pangaea, Greek for "all land," the name Wegener gave to the ancient super-continent, formed
over 250 million years ago. As Pangaea began to break up, the amount of shoreline increased.
and the shape and size of the oceans on the globe changed. New life forms flourished. with
these changes. The continents sitting on their plates continue to slowly drift, collide and
reshape the face of our globe.
FAULT ACTION:
California is laced with a network of active geologic faults, or weak fracture zones in the rock
formations that underlie the state. The San Andreas Fault System describes the entire complex
of faults that spread out along the entire length of the San Andreas and includes the Hayward
Fault and many of the smaller faults that transverse the San Francisco Bay Area. California has
the distinction of being the boundary between the Pacific and North American Plates. As the
two plates grind past each other, the resulting friction causes strain to build up in the rocks
deep within the earth. Eventually the rocks break apart and move to a new position, releasing
energy in the form of earthquakes. After this release of energy, new strains begin to build along
the fault, starting the next stress release cycle.
Plate movements and their accompanying earthquakes and volcanoes have created a unique
and scenic landscape in California. In addition to existing signs of ancient and recent volcanic
action on the landscape, there are other fault features such as linear mountain ranges and
ridges (like the San Gabrielle mountains in Southern California), steep gullies or saddles along
ridges, sunken blocks (San Francisco Bay was deepened by a huge sunken block and the
upward thrust of land on each side, caused by action along the Hayward and San Andreas
faults), scraps or broken ground surface, landslides, offset streams, sag ponds, and springs. The
influence of the northwest-trending San Andreas Fault can be seen in a variety of linear
landscape features.
Plate tectonics is based on the theory that all plates are in motion. One principle of the plate
tectonics theory is that each plate moves as a distinct unit in relation to other plates. As plates
move, two locations on the same plate stay the same distance from each other while the
distance between locations on opposite plates may change constantly. There are four types of
plate movement:
© Environmental Volunteers
Earthquakes
Plate Puzzles
EQ – 03 & 04
page 3
Seafloor Spreading occurs primarily on the ocean floor — in long "seams" in the Atlantic
and the Pacific; however, there are also rare instances of land rifts. These areas are also
known as "rift zones" and are characterized by parallel mountain ridges on both sides of a
valley, and a spreading zone where new magma is rising to fill the growing gap. Plate
spreading can be seen occurring on land in Iceland, and in Africa's Rift Valley; the effects
on the landscape are quite dramatic. Eventually plate movement along Africa's rift will
cause the Mediterranean Sea to become completely enclosed. Knowledge of mid-ocean
ridges came from soundings taken of the ocean floor, core samples from deep-sea drilling
and visual inspection using deep-diving submersibles.
Subduction action occurs in a variety of places around the globe, such as the western coast
of South America, along the Aleutian Island chain, and along the coast of Washington and
Oregon. One plate sinks beneath another forming a trench; the Chilean trench is a good
example. Usually a heavier oceanic plate moves under a lighter continental plate. Coastal
mountain ranges and chains of island volcanoes often indicate that subduction has been at
work.
Collision action occurs over geologic time and is always continental. This type of
movement has formed the Alps and the world's highest mountains, the Himalayas. The
collision of the Indian-Australian Plate with the Eurasian Plate continues to build this
awesome chain of mountains.
Transform fault movement is the kind of plate interaction Californians are most familiar
with – the Pacific Plate grinding past the North American Plate along the San Andreas
Fault. The boundary is actually one long transform fault connecting two zones of plate
spreading. Knowledge of movement has been obtained by bouncing laser beams from the
North American Plate to distant hills on the Pacific Plate.
They are oriented in the same or similar direction, and may appear as streams, which, if
they happen to cross the fault zone, are "offset" or displaced from their original path. Fault
zones range from 100 yards to a mile or more in width and up to hundreds of miles long.
Fault movement along the San Andreas is of different types, vertical movement called reverse
or thrust and normal, and horizontal movement called transform. Vertical movement is not as
common, but did occur during the 1989 Loma Prieta earthquake as part of that mountain range
rose approximately four feet, and in the 1991 Sierra Madre earthquake where the mountains
were pushed upward the same distance. Most San Andreas fault action is horizontal, resulting
in the creeping movement of the Pacific Plate past the North American Plate. Movement along
the San Andreas is often described as "right-lateral," for when you look across the fault trace to
the other side, objects there have shifted sideways to the right.
Fault action triggers earthquakes, and in California thousands of quakes are recorded each
year. Most of the tremors go by unnoticed or cause minor damage. Every so often though, a
major quake rips along a portion of an active fault, adding new features to California's
earthquake landscape. Evidence from seismic records indicate that earthquakes originate at
depths ranging from 3 (5km) to nearly 434 miles (700km). In California, the earthquakes are
shallow, rarely reaching depths of 9.3 miles (15 km). The location on the earth's surface that lies
directly above the focus of an earthquake is known as its epicenter. Waves of energy spread out
from the focus becoming weaker as they travel farther from the epicenter.
© Environmental Volunteers
Earthquakes
Plate Puzzles
EQ – 03 & 04
page 4
ACTIVITY:
TIME: 15 to 20 minute activity
PREPARE:
Arrange to have an area with plenty of open floor space and enough room for the
audience to stand around the perimeter of the RUG to observe. Have PLATE PUZZLE
MAP, NAME CARDS & ARROWS, CALIFORNIA MAP(S), LOCAL MAP(S) and ROCK
SAMPLE ready for display
AUDIENCE:
Younger children (grades 2 – 4) – With some help and guidance, the PUZZLE RUG and
MAP can be fun activities that can be built on later. Encourage participation.
Older children (grades 5 – 8) – Point out that the plates have been moving for millions of
years and will continue to do so. As a result, we can expect major and minor
earthquakes in California and on other plate boundary areas
Adults: – Highlight the inevitability of plate movements and earthquakes and the need
to plan and prepare for the major quakes to come
Display the PLATE PUZZLE MAP and point out the 12 major plates.
EXPLAIN:
To show the movements of a few of these plates, we will use the PLATE
PUZZLE RUG. Have 3 or 4 volunteers unfold the rug and put the plate pieces together.
DO :
Point out the ocean floor features on the PLATE MAP.
DO :
Offer help if needed in putting the RUG together, especially with younger children.
DO :
Place plate labels on the rug pieces using the PLATE MAP as a guide. You can also use
the PLATE PUZZLE CUT-OUT MAP (insert in folder) as a guide to placing ARROWS
AND LABELS on the RUG.
ASK: Which way are the plates moving?
DO :
Encourage participation in describing plate movement.
ASK: According to the arrows, what is happening where the plates meet?
DO :
After a few verbal responses, ask for volunteers to demonstrate the movements on the
RUG.
DO : Have a few people slowly pull the rug pieces in the direction the arrows point, and
show three different types of boundaries.
NOTE :Some guidance may be needed. Make sure the plates are moved very slowly so the
effects can be observed.
DO :
Demonstrate SPREADING at the Atlantic and the Pacific rift zones on the PLATE
PUZZLE RUG.
DO:
Display the BASALT ROCK SAMPLE it is the kind of rock found in the sea floor
spreading zones in the Atlantic and the Pacific rift zones.
ASK : Does this mean the earth is expanding?
RESPONSE: No.
ASK : How does spreading affect the other plates?
RESPONSE : Plates must recycle back into the mantle elsewhere.
© Environmental Volunteers
Earthquakes
Plate Puzzles
EQ – 03 & 04
page 5
DO:
Demonstrate SUBDUCTION as along the Aleutian Islands Trench and the west coast of
South America. Make sure the edge of the subducting plate goes under the other plate.
DO :
Demonstrate COLLISION as in the Himalayan Mountain area.
DO :
Demonstrate TRANSFORM FAULT movement where the Pacific Plate grinds past the
North American Plate.
EXPLAIN:
areas.
DO :
Transform fault movement results from spreading and subduction in other
Point out the California area and demonstrate the plate movements there.
ASK : Which way are the plates moving?
RESPONSE : The Pacific Plate is grinding past the North American Plate in a northwesterly
direction.
ASK : Why do we have so many earthquakes in California?
RESPONSE : The rocks of the two moving plates tend to lock together, building up great
stress or tension along the boundary. Earthquakes frequently release some of this constantly
building stress.
DO :
Display the RELIEF and FAULT MAPS, and on the MAPS trace the San Andreas Fault.
DO : With younger audiences, have them trace the San Andreas Fault with their fingers.
Offer assistance in measuring and computing the distance from their homes to this Fault.
DO :
On the local RELIEF or FAULT MAP, have a few people point out where they live.
ASK : Each volunteer how close to the San Andreas Fault do they live?
ASK : What will happen to California in the future?
RESPONSE : Los Angeles will pass San Francisco and the Pacific Plate part of California will
become an Island in approximately 10 million years.
DO :
Demonstrate the present and future of California with the RUG,
FOLLOW-UPS:
Leave the teacher with a master copy of the "PLATE PUZZLE CUT-OUT MAP" insert. They can
color and cut out the plates to be used as a puzzle.
Write a story of what life on the "Island of California" (the section of California that is on the
Pacific Plate) will be like 40 million years from now.
Make a "flip-book" of maps of California showing the changes from 40 million years ago to 40
million years from now.
REFERENCES:
Geological Museum. The Story of the Earth, North American edition, pp. 11 – 13.
Calder, Nigel. The Restless Earth, A Report on the New Geology.
© Environmental Volunteers
Earthquakes
Plate Puzzles
EQ – 03 & 04
page 6
© Environmental Volunteers
Earthquakes
Plate Puzzles
EQ – 03 & 04
page 7