i can understand continental drift what’s the sea got to do with it? · 2020-02-07 · how does...

What’s the sea got to do with it?

I can understand

what sea-floor

spreading is by

using evidence

from the

Continental Drift

Theory.

3 IMPORTANT THINGS to LOOK for and KNOW

1. What is seafloor spreading?2. Which scientist suggested that seafloor

spreading supported the Continental Drift Theory?

3. How does Seafloor Spreading support the Continental Drift Theory?

Mid-Ocean Ridges ● What are they?

Mid-Ocean Ridges curve

like the seam of a

baseball along the Earth’s

sea floor. They are very

similar to mountains and

valleys in the ocean.

Sonar Sonar - short for Sound Navigation and Ranging, helps to explore and map the ocean because sound waves travel farther in the water than do radar and light waves.

Sonar A device that

bounces sound waves

off underwater

objects and then

records the echoes

of these sound

waves.

The time it takes

for the echo to

arrive indicates

the distance from

the object.

Harry Hess **● The mapping of mid-ocean

ridges made scientists

curious to know more about

them by trying to explain

how they are formed.

● Harry Hess, an American

geologist was curious

about mid-ocean ridges.

Harry Hess ● He began to think about the ocean floor

in relation to the problem of

continental drift.

● In the 1960’s Hess suggested that the

continents do move in a process called

sea-floor spreading.

Sea-floor Spreading

Sea-Floor SpreadingThe sea floor spreads

apart along both sides of

a mid-ocean ridge as new

crust is added.

As a result, the ocean

floors move like

conveyor belts, carrying

the continents along

with them.

Sea-Floor Spreading **

Molten material erupts through the

valley that runs along the center of some

mid-ocean ridges.

This material hardens to form rock on the

ocean floor.

Stop and Think?So, what happens to

the rock along the

ridge when new

molten material

erupts?

Evidence of Seafloor Spreading** Several types of evidence support

Hess’s theory of seafloor

spreading.

★ Eruptions of Molten Material

★ Magnetic Strips in rock of the

ocean floor.

★ The ages of rocks themselves.

Eruptions of Molten Material ● In the 1960’s, scientists found evidence that new

material is indeed erupting along mid-ocean

ridges.

● During their deep water dive in a specialized

submarine (Alvin) they discovered strange rocks

shaped like pillows and toothpaste that had been

squeezed out of the tube.

Eruptions of Molten Material● Such rocks only form when molten material harden

quickly after erupting underwater.

● These rocks showed that molten material has

erupted again and again along the mid ocean

ridge.

Magnetic Strips in rocks of the ocean floor● Scientists discovered

the rocks that make up

the ocean floor lies

in a pattern of

magnetized “stripes.”

Magnetic Strips in rocks of the ocean floor● The rock on the ocean floor contain bits of iron.

When the new molten rock being to harden and

take form the bits of iron line up in the

direction of the Earth’s magnetic poles giving

the rocks permanent “magnetic memory.”

The Age of Rocks Themselves ● This proof came from rock samples obtained by

drilling into the ocean floor.

● They found that the farther away from a ridge the

samples were taken, the older the rocks were.

● The youngest rocks were always in the center of the

ridges.

How does seafloor spreading support the theory of continental drift?

In your notebook: Please answer the

following question. You must use complete

sentences and explain your understanding

of the material presented. This will be

graded for a 10 point homework grade.