Extreme Deep Teacher's Guide.pdf - Evergreen Exhibitions

Seafloor Spreading Centers
OBJECTIVES
Students will discover that...
■ the Earth’s crust is made of several sections,
called plates. The plates move slowly over time,
changing the positions of the continents.
■ the Earth’s crust is always changing. Sometimes
these changes result in earthquakes, volcanic
eruptions and mountain building.
■ new crust forms at seafloor spreading centers,
where magma erupts and cools.
S U B J E C T S
geology, geography
G R A D E S
5 - 7
C O N C E P T S
plate tectonics
D U R A T I O N
one to two 45-minute class sessions
BACK
CKGROUND INFORMA
RMATION
Some of the most exciting discoveries have been made by accident. One such recent discovery
happened when scientists went down into the deep sea to study areas of the ocean floor called
seafloor spreading centers. What did they find by accident?
According to the theory of plate tectonics, the earth’s crust is composed of approximately 20 large
sections called plates that piece together like a jigsaw puzzle. Over time, these plates move,
shifting the position of the continents relative to each other. The shifting of plates is one cause of
earthquakes.
Seafloor spreading centers mark the birthplace of Earth’s plates. Volcanic eruptions spew molten
rock into the deep sea, where it quickly cools and becomes new seafloor. Over time, eruptions
slowly push the plates outward. The edge of the plate being formed is called the trailing edge. The
opposite edge is the leading edge. Because it’s farthest from the seafloor spreading center, it’s the
oldest edge. Where the leading edge of one plate meets the leading edge of another, the two
collide. Often, one plunges under the other and a deep trench forms. It is in these trenches that the
seafloor is forced deep into the Earth.
With this activity your students will piece together pieces of the earth’s crust to see plate tectonics in action.
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