Changing Earth
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  • Introduction
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The Earth has an iron (inner and outer) core surrounded by a mantle. The outside is a thin, rocky crust. You can see the Earth's structure in the diagram below:

 


The outer layer of the Earth is called the lithosphere. It is made of the crust and the upper part of the mantle. The Earth's crust is made of tectonic plates (see diagram below) that are less dense than the mantle, so they float on it. There are two types of plates: continental, which carry the continents, and oceanic, which lie underneath the oceans. Continental plates are less dense than oceanic ones. Tectonic plates move slowly apart or collide and even scrape sideways past each other. When plates collide, the denser oceanic plate slips below the continental one; this is called subduction and the vibration causes earthquakes.

 

 


The Earth's atmosphere is also changing due to pollution. Carbon dioxide in air has increased, because more fossil fuels are being burnt, as the world's population increases and deforestation means there are fewer trees to release oxygen into the atmosphere by photosynthesis.


Pollutant gases are carbon monoxide (poisonous), oxides of nitrogen (photochemical smog, acid rain) and sulfur dioxide (acid rain). Cars are now fitted with catalytic converters to reduce the amount of these pollutants.

  • Question 1
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What do we call the layer underneath the Earth's crust?

  • Question 2
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What makes the Earth’s crust?
air

water

rock

  • Question 3
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What makes the Earth’s lithosphere?
crust

core

the whole of mantle

upper mantle

  • Question 4
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What are the two types of tectonic plates?
continental

oceans

oceanic

continents

  • Question 5
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What describes the movement of the tectonic plates? Tick three options.

They move apart

They go up and down

They collide

They move sideways

  • Question 6
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Is the following statement true or false?

 

Continental plates are denser than oceanic plates.

true

false

  • Question 7
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What is subduction?

When the denser continental plate slips below the oceanic plate.

When the denser oceanic plate slips below the continental one.

When the two plates collide.

  • Question 8
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What causes less oxygen to be released into the atmosphere?

deforestation

global warming

fractional distillation

  • Question 9
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What does sulfur oxide cause in the atmosphere?

deforestation

the ozone layer

acid rain

  • Question 10
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Select the poisonous gas.

sulfur dioxide

carbon monoxide

carbon dioxide

Progress