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C1 Our Changing Planet

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The Earth
The Atmosphere
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The Earth

The Earth is made up of three main layers:

  1. crust (rocky)
  2. mantle (solid, but can flow very slowly)
  3. core (made from liquid nickel and iron)
A diagram showing the different layers of the planet.

Tectonic Plates

The Earth's crust is made up of large areas called tectonic plates. They are constantly moving tiny amounts every year, and this moved leads to continental drift.

Convection currents in the mantle cause the plates to move, either on top of each other (land 'disappears') or crumpling together forcing land up (making mountains), or the plates move apart 'creating' land.

How the Earth is split into different tectonic plates.

Wegener's Theory

The theory of continental drift was suggested by Alfred Wegener. Before his idea it was thought that the Earth had formed mountains as it was 'cooling' and that it was shrinking because of this - forming wrinkles, or mountains, in the Earth's crust.

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Modern Atmosphere

Today's atmosphere is made mainly of nitrogen (78%) and oxygen (21%). The remaining 1% of gases is made up of argon, carbon dioxide and other gases.

Composition of Earth's and Mar's Atmospheres

Early Atmosphere

The planet is believed to be about 4.5 billion years old, and that the early atmosphere probably formed due to gases given out by volcanoes leading to a high concentration of carbon dioxide in the atmosphere. It is also thought that simple life formed that was capable of turning carbon dioxide into oxygen (photosynthesis), which is why we have much more oxygen today.



This experiment was conducted by two scientists in the 1950s. It saw a combination of gases (water, ammonia, methane, hydrogen) which were thought to be in abundance in the early atmosphere. The conditions are described in the following video, and this experiment was conducted to see if it was how life formed.

Another theory suggests hydrothermal vents created the primordial soup.

Separating Air


Fractional distillation is a method of separating crude oil, but a similar process can be completed for separating the gases in air!

Some uses of the gases:

  • liquid nitrogen is used to freeze food
  • food is packaged in gaseous nitrogen to increase its shelf life
  • oil tankers are flushed with gaseous nitrogen to reduce the chance of explosion
  • oxygen is used in the manufacture of steel and in medicine.

Carbon Dioxide

Photosynthesis had a big part to play in removing carbon dioxide from the air, but there were other things that happened too:

  • dissolving in the oceans (becoming slightly acidic)
  • the production of sedimentary rocks such as limestone
  • the production of fossil fuels from the remains of dead plants and animals

Burning fossil fuels (coal and oil) is adding carbon dioxide back into the atmosphere faster than it can be removed by any of the methods above, adding to global warming. It also means that bodies of water, and rain, are becoming more acidic.

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Page last updated: 16/04/2017