Seafloor Spreading + Layers of the Earth

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​Glacial scars in Africa tell us that Africa USED to be closer to the South Pole.

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Glaciers in Antarctica then moved into southern African and left glacial scars.​

​Fill out the notes as we go!

​Alfred Wegener was the scientist who proposed the Continental Drift Theory.

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His evidence included:

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1. ​Edges of continents looked like…

1. Mountains…

2. Fossils…

3. Coal deposits…

4. Climate clues...

​Wegener

​Why was Alfred Wegener's theory NOT accepted?

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​Wegener

​Wegener

What was the problem?​

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Wegener couldn't explain WHY or HOW the continents moved!

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The scientific community needed more than what Wegener had.

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Later, Harry Hess made a discovery that helped!​

Multiple Choice

What did Hess discover?

• Underwater volcanoes called a mid-ocean ridge

• Underwater trench called the Mariana Trench

• A volcanic island off the coast of Taiwan

• Hydrothermal vents in the deep sea

Multiple Choice

What did Harry Hess call the process that created the mid-ocean ridge?

• Earthquakes

• Converging boundaries

• Seafloor spreading

• Transform boundary

​--> mid-Atlantic

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​--> magma

​--> new crust

​--> spreading

​Graph the Mid-Atlantic Ridge!

​What is causing seafloor spreading? To understand, we must look at the layers of the Earth.

​Crust, where we live. Broken in pieces called "tectonic plates"

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Two types of crust: Oceanic and Continental.​

​Oceanic

Crust​

​Continental

Crust

​Inside of your notes:

​What is the difference between the continental crust and oceanic crust?

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Continental crust is LESS DENSE, the oceanic crust is MORE DENSER.

​The hottest layer of the Earth is the core. It heats the mantle above it. When the magma heats up, it rises.

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What effect might this have on the crust?​

​Oceanic

Crust​

​Continental

Crust

​Inside of your notes:

​Inner

Core​

​Outer

Core​

​Mantle

​Convection in the Mantle

​Hot magma rises, cold magma falls.

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What do we call this process of hot rising and cold falling/sinking?​

Multiple Choice

The hypothesis that land masses spread apart from each other and have done so in the past is known as

• Seafloor Spreading

• Continental Drift Theory

• Uplift of the crust

• Continental Spreading

Multiple Choice

Where does sea-floor spreading take place?

• Convergent Boundaries

• Transform Boundaries

• Land Boundaries

• Mid-Oceanic Ridges

Multiple Choice

What is the thinnest layer of the Earth?

• Crust

• Mantle

• Outer Core

• Inner Core

Multiple Choice

What is the thickest layer of the Earth?

• Crust

• Mantle

• Outer Core

• Inner Core

Multiple Choice

When the Crust sinks down into the Mantle what happens to it?

• It becomes a tectonic plate

• It slowly floats up

• It Melts

• It sinks to the inner core

Multiple Choice

Which type of crust is MORE dense?

• Oceanic

• Continental

• They are both the same density

Multiple Choice

What do we call the process of HOT magma rising and COOL magma sinking?

• Magma recycling

• Convection Currents

• Molten uplift

• Lava currents

Multiple Choice

What is a mid-ocean ridge?

• A underwater hydrothermal vent

• A underwater fault line

• A range of underwater volcanoes

• An underwater valley