Page 160 - Science Course 2 (Book 2)

Mo11-L5b: Evidence Supporting Seaf oor Spreading

Or, as the lava cools and forms new crust, it cracks Evidence Supporting Seaf oor
and the rocks move up or down along these cracks Mo11-L5b Spreading
in the seaf oor, forming jagged mountain ranges.
KEY CONCEPTS:
The abyssal plain, the smooth part of the seaf oor, is 1. What evidence is used to support seaf oor
made when the layer of sediment that accumulates spreading?
far from the mid-ocean ridge becomes thick enough.

abyssal plain Vocabulary A-Z
Let us learn some vocabulary

normal polarity
when magnetized objects, such as a compass
needle, orient themselves to point north.

Continents move as the seaf oor spreads along a
mid-ocean ridge.

SUMMARY
What is Seaf oor Spreading?

New ocean crust forms along mid-ocean
ridges.
magnetic reversal
Mid-ocean ridges are large mountain ranges an event that causes a magnetic f eld to reverse
that extend throughout Earth’s oceans. direction.

N N

S S

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