C1bL11 Earth

Key Words

Atmosphere - layer of gases surrounding a planet..

Core - The material right at the centre of the Earth or other planet

Crust  - Top layer  forming the surface of a planet.

Magnetic field - region of force that acts to attract a magnetic material.

Magnetic poles - Points from which magnetic field lines emerge.

Mantle - layer below the crust.

Planet - a large body that orbits a star.

Star - a large body that gives off energy due to fusion reactions.

 

Test Yourself

Homework
Subject Page
Home

Grade E

The Earth is a planet that orbits about the Sun, the star at the centre of the Solar System.  Its diameter is about 13 000 km and it's slightly flattened at the poles.  Facts about the Earth include:

  • It has a layer of mixed gases around it, the atmosphere.
  • It's a rocky planet.
  • 70 % is covered by water.
  • It is 4500 million years old.
  • It has had life on it for about 3400 million years.  Humans have been about for around 30 000 years.
  • It has one satellite, the Moon, of diameter 3500 km

Other planets in the solar system are bigger.  Jupiter is about 11 times the diameter of the Earth.  Jupiter has no solid surface.  It is thought to be a failed star.

Conditions on the Earth are just right for life.  Venus is too hot, while Mars is too cold.  It's called the "Goldilocks Effect".

Grade C

Scientists have found that the Earth has a layered structure like this:

  • The atmosphere consists of air, a mixture of gases, 78 % nitrogen, 21 % oxygen, and 1 % of lots of other gases.

  • The crust is relatively thin.  It is solid rock and covers the Earth..

  • The mantle is very hot so that the rock is semi-liquid.  The very viscous fluid is heated by radioactivity.  The heat makes convection currents, which drive the movement of continents.

  • The core is made up of iron and nickel.  The outer part is liquid, and the inner part is solid.  The movement of the the liquid outer core is thought to cause the Earth's magnetic field.

  • The magnetic poles change over from time to time.

Grade A

The Earth's magnetic field is like that of a bar magnet.  It shields us from charged particles from the Sun, the solar wind.  The magnetic field is known to change over time.  Some scientists have observed that the magnetic field has lost about 10 % of its strength in 1850.  At this rate it could be switched off in about 2000 years time.  The effects of this would be:

  • Birds would not be able to navigate;
  • Aeroplane pilots could not rely on magnetic compasses.
  • Charged particles from the Solar wind could damage living material.

Then the magnetic field will come back again, but this time reversed.  Compasses would point South.