Page 158 - Science Course 2 (Book 2)

Seaf oor Spreading Mo11-L5a: What is Seaf oor Spreading?
Lesson 5

Let’s Begin

In this topic, you will learn the following
lessons:
Mo.11–L5a: What is Seaf oor Spreading? Mapping the Ocean Floor
Mo.11–L5b: Evidence Supporting Seaf oor During the late 1940s scientists were able to
Spreading determine the depth of the ocean using a device
called an echo sounder.

Mo11-L5a What is Seaf oor Spreading?

KEY CONCEPTS:
1. What is seaf oor spreading?

Vocabulary A-Z

Let us learn some vocabulary

mid-ocean ridge
long, narrow mountain range on the ocean f oor;
formed by magma at divergent plate boundaries.

Once ocean depths were determined, scientists
used these data to create a topographic map of the
sea f oor that revealed vast mountain ranges, called
mid-ocean ridges, that stretch for many miles deep
below the ocean’s surface.

seaf oor spreading

the process by which new oceanic crust forms along
a mid-ocean ridge and older oceanic crust moves
away from the ridge.

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