Grade Six Science
Hello Boys and Girls,
How was your first week back at ‘school’? Did you spend your time wisely, paying attention to all that there was to be learnt? This week we will look at the earth, as we remember our Caribbean neighbour, St Vincent, which is experiencing difficult times.
The earth is a huge ball of rock, metal, water and air. Only three-tenths (3/10) of the earth’s surface is land. The rest (what fraction would that be?) is covered with water. A thick layer of gases surrounds the earth. This layer is called the atmosphere.
It is generally believed that, in its present state , the earth has three major layers. Can you name them? Yes, the core the mantle and the crust.
The outermost part of the crust varies in how thick it is. It is thickest where you find land or continents. It is thinnest under the sea or oceans. The earth is like a breadfruit, someone once said. The crust is like the skin, but it has more bumps. The bumps are where there are high mountains. The hollows are underneath the oceans.
Look at the picture below and you will see the various layers that make up the earth.
Answer these questions
● What is the outermost part of the earth is called?
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The core of the earth is believed to consist chiefly of a liquid mixture of iron and nickel. Surrounding this core is the mantle. This mantle is considered to be a shell of heavy rock up to about 1800 miles ( how many kilometres would that be?) and it is exceedingly hot. Surrounding the mantle is a thin outer crust. This crust is about 40 to 50 kilometres thick and it contains fuels, minerals, rocks and soil. If we compare the earth to an apple, the crust of the earth is like the skin of the apple.
What fraction of the earth’s surface is land?
What is the layer of gases around the earth is called?
What is the name of the layer surrounding the core of the earth?
Compare your answers with those of your friends.
Let’s continue our investigation of the earth.
Let’s make a simple model of the earth. You will need plasticine of different colours and a knife.
1. First roll one of the colours of plasticine into a ball. This will represent
the core. (It will have to be solid since you cannot make the liquid part.)
2. 3. 4.
Some exercises for you –
How many words to do with earth can you find in the squares below? List them. You can move from letter to letter in any direction.
Change a letter in each of the following words to make a word related to earth:
Foil Soot
Next put another thick layer of plasticine all around the core. What does this represent? Yes, this represents the mantle.
Now on the outside make a very thin layer of another colour. This rep resents the crust but do remember to make the crust a bit thicker in some places to show the land or continents.
Make a few cracks in the crust. This can happen if you put the crust on in pieces, overlapping them slightly on the mantle.
Cut your model in half with a knife – from the crust down to the core. Do you see the layers?
Different parts of the earth’s crust tend to move from time to time. When this happens sometimes a crack develops. Parts of the earth may slide past each other where there is a crack. This makes an earthquake develop. If you have ever felt a slight earthquake or earth tremor you will have had some idea of the movement of the earth’s surface.
In Guyana we are very fortunate to not experience any (just a few tremors). Scientists know that the earthquakes occur where there are cracks in the earth’s crust, but they do not know exactly when they will happen or if they will be big or small.
Can you name any countries where earthquakes have occurred?
Have you ever heard of a volcano? I am sure that you have been hearing about the volcano that erupted in St Vincent over the last few days. Can you list at least two places where they have erupted? Hot liquid material called magma, from inside the earth, shoots up from the volcano, and spreads out as lava. Gas and ash are also sent high up into the air and an explosion is heard. We understand that ashes are all over the island and have even reached the island of Barbados.
This is all for now.
Pore Plane
Sock
Until next week, goodbye Boys and Girls! Do remember to remain safe, wash your hands regularly and wear a mask if you really must go out.