VHS+Science+Lesson+02

Today we are going to learn about Earth (the planet we live on) and how it changes.

What do you see between South America and Africa?

How could South America and Africa fit together?

How does Earth remind you of a puzzle?



= = = Big Idea = Earth has 3 layers. Under the surface, rock is hot enough to become soft. When soft rock rises toward the surface, it can move plates. When plates move, continents and oceans move, and volcanoes and earthquakes can form.





The Earth has an outer layer called the crust that is made of pieces called plates. The crust is cool compared to the mantle.

Earth has a middle layer called the Mantle. The mantle is warm.

Earth has a center layer called the core. The core of Earth is very hot.

= Analyzing Evidence =

Evidence is data about something that happened. Scientists analyze evidence to form a theory. For example, scientists observed things they could see on the surface of the Earth. They analyzed their observations to form the theory of plate tectonics. Look at the web. When you analyze evidence, you decide what it means. Here is one way to do this.

1) Think about what one piece of evidence means and write down your idea.

2) See if other evidence means the same as the first piece. If it does not, revise your idea.

Earth is very, very old. This timeline shows Earth's history, from it's beginning to the present.



= Understanding Earth =

Earth has 3 different layers. The inside layers are hot. This heat makes rocks soft. Plates move because the soft rock is moving. This can cause volcanoes and earthquakes to form.
Earth has 3 main layers. Oceans and continents make up it's top layer.

The crust is Earth's outside layer. It is the layer where we live. Compared to the other layers, the crust is thin and cool. Cool rock is strong.

The mantle is Earth's thick middle layer. Rock in the mantle is softer than rock in the crust. That's because the mantle is hot enough to melt rock. Hot rock can bend and move.

The core is at Earth's center. The core is the hottest layer of Earth.

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Part 2

Let's do a quick review of our previous lesson on the layers of the Earth.

= Oceans, Continents, and Plates. = Oceans are big areas of salty water. They cover most of Earth's surface. Continents are very big areas of land.

Plates are under the oceans and continents. Plates are thick pieces of crust that can move. Earth's surface is broken into 11 big plates and 10 to 20 small plates. A continental plate has a continent on it. An ocean plate has an ocean on it.



=How Plates Move=

There are mountains on the surface of the Earth. Mountains are beneath the ocean water, too. There are trenches in the ocean bottoms. Trenches are deep, low areas that are very long.



What makes mountains and trenches? Scientists developed a theory to answer that question.

Now before we hear the theory remember, a theory is an idea that explains how or why something happens. A theory must have evidence to support it.

The theory of plate tectonics explains how mountains and trenches are made. It states that the plates on Earth do not stay in one place. Heat in the mantle cause the plates to move.

media type="custom" key="26348928" www.youtube.com/watch?v=ryrXAGY1dmE



Do we have any place like this where we live? Yes, it's known as the San Andreas Fault.





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https://www.youtube.com/watch?v=ZxPTLmg0ZCw

Part 3:

= Volcanoes and Earthquakes =

Volcanoes and earthquakes are caused by changes inside Earth. Some places have a lot of earthquakes and volcanoes. These places are on the edges of plates. A volcano forms above cracks in Earth's surface. Heat below the surface melts rock. Melted rock inside Earth is called magma.

Magma rises toward the surface. When magma spills onto the surface, it is called lava. Lava cools as it moves away from the volcano. Cooled lava turns into hard rock.





media type="custom" key="26349056" (8:45) https://www.youtube.com/watch?v=3zHgwiOK3oU =Earthquakes=

An earthquake is a sudden release of energy caused by moving rock. Many earthquakes happen where two plates scrape against each other. The movement makes energy build up until the rock breaks. A crack where rock breaks and moves is called a fault.







The ground shakes in an earthquake. After a big earthquake, the ground may shake for or weeks. Each shake gets a little weaker. When rock along the fault completely sattles into its new position, the shaking stops.

Here is a video of a "Hollywood earthquake"... it's not real folks.

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https://www.youtube.com/watch?t=43&v=PJLuDAwSKLo

Here is a video of a real earthquake.

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https://www.youtube.com/watch?v=ML41i2AN7K0

Here are some pictures of damage from an earthquake.







What should be do if an earthquake happens?