Key Terms: mid ocean ridge, sea floor spreading, core samples

Mid Ocean Ridge Review Turn to page 81 in your textbook.Discovered by using sonar during the 20th

century.Find the mid ocean ridge that bisects the

Atlantic Ocean.Lets look at the GIS.

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Mid Ocean Ridge

Sea Floor SpreadingTurn to page 82 in the your textbook.Sea Floor Spreading:

A concept proposed by American geologist Mr. Harry Hess.

Mr. Hess proposed at the mid ocean ridge: Molten material rises from the mantle and erupts. The molten material then spreads out on both sides of the

mid ocean ridge. As the molten material spreads out, it pushes older rock

to both sides of the ridge. Lets look at the animation .

Evidence that supports the theory of Sea Floor Spreading:

Evidence from ocean material. Evidence from magnetic stripes. Evidence from drilling samples.

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What is a drilling or core Sample?A sample of rock, soil, snow, or ice obtained

by driving a hollow tube into the undisturbed medium and withdrawing it with its contained sample or core.

Core samples were taken from all over the sea floor. Core samples were returned to the surface where they were studied.

The age (how old or how long ago it was formed) of the rock can be determined from the core sample.

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Visual Evidence for Sea Floor Spreading

First, observe and manipulate the on line interactive activity.

Next, lets observe a GIS map of the sea floor age at the mid ocean ridge.

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Mid Ocean Ridge

Map of theSea Floor Age

Visual Evidence Thought Questions.Is the age of the sea floor younger or older

close to the mid ocean ridge?Is the age of the sea floor younger or older

farther away from the mid ocean ridge?On either side of the mid ocean ridge are the

sea floor ages random, or do you see a pattern?

Describe the pattern you observe.

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Is the Earth Getting Bigger?

If the sea floor is spreading, why isn’t the

Earth getting bigger? (of course

not)In our next lesson we’ll find out why!

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