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  • What is the External Structure of the Erath?

    What is the External Structure of the Erath?

    What is the External Structure of the Erath?

    It has been known for more than 2000 years that the Earth is round, but we were able to actually see this much later only when we flew into space.

    The knowledge why we do not fall off from the Earth is much more recent.

    A journey as described by author Jules Verne in his book Journey to the Center of the Earth was, after all, impossible. Only one thing was known:

    the Earth is made up of soil, rocks, and water. Today, we know that the Earth is also surrounded by an air cover called the atmosphere.

    What is the internal structure of the Earth?

    Like an onion, the Earth has several layers. The outermost layer, the Earth's crust, has an average depth of about 40 km. As compared with the diameter of the Earth, which is around 12,700 km, the Earth's crust is very small. It is primarily made up of solid rocks. Below the crust is the mantle, reaching to a depth of about 2900 km. Due to the heat inside the Earth, the mantle consists of solid and molten rocks, Below the mantle is the core, made up of iron and nickel. The deeper one travels inside the Earth, the hotter it is. The temperature in the core is between 4000 and 5000°C.


    Sold Earth's crust (0-40 km)

    Molten outer Earth core (2900-5100 km)

    Solid inner Earth core (5100-6371 km)

    Convection cells in the Earth's mante Hot material ribes up cold material sinks down (speed about 2-3 cm year)

    Solid to viscous Earth mantle (40-2900)

    How do we discover what is inside the Earth?

    Caves and mines go only up to 1-2 km inside the Earth. Even the deepest wells of the world, such as the one 12 km deep in the Russian Kola Peninsula or the 9-km-deep one in the Upper Palatinate, hardly scratch the Earth's crust.

    One can"look' deep inside the Earth in the aftermath of earthquakes or by creating nuclear explosions. The explosions generate sound or seismic waves. They also throw off rock particles. By measuring their intensity and timings, scientists discover the composition of the Earth's interiors.

    The Continental Deep Drilling, near the Bavarian city of Weiden drilled a hole around 9 km deep in an old mountain. The drilling rig was over 80 m high

    How did we discover that the Earth is round?

    About 3000 years ago people believed that the Earth was flat. But people wondered why ships disappeared at the horizon.
    Sailors to return from journeys and were proof that ships did not fall off the edge of the Earth. The simplest explanation was: the Earth must be round. The final proof came in the year 1522 after the expedition of Ferdinand Magellan, who was the first to sail around the Earth.


    The continental deep drilling,near the bavarian city of weiden, driled a hole around 9km deep in an old mountain. The drilling rig was over 80m high.

    The disappearing cut
    You need: An exercise ball, a small toy car, about 1m of thread
    Do as follows: Tie the thread to the car. Place the car on the ball and place it in front of you. Now, holding the thread let the car roll away from you.

    Why do we not fall off from the Earth?

    Gravity is the force of the Earth that attracts every object towards itself. From our perspective this force always acts downwards. For a long time people did not believe that the Earth is round because then the people 'underneath' the sphere would have tually fallen down. In 1687, a physicist, Isaac Newton, proved that the force of gravity always acts towards the centre of the Earth. On the Earth, the force of gravitation always acts 'downwards' irrespective of Eskimos in the Arctic region, people in Europe or inhabitants of australia.

  • more than 2200 years ago, the Greek discovered that the Earth is round? They even calculated an almost accurate circumference of the Earth.
  • the Earth is not a perfect globe? Its circumference at the equator is 40,077 km, whereas measured over the poles it is 68 km less.
  • 'atmosphere' is a Greek word which means 'ball of vapour?

  • What is the atmosphere made up of?

    The word 'atmosphere' means a gaseous cover enveloping a planet. Without atmosphere life would not have been possible on the Earth: One-fifth of the atmosphere is oxygen and four-fifths is nitrogen. Like the Earth's interior, the atmosphere too is made up of several layers. All animals and plants live in the lowermost layer of the atmosphere called the 'troposphere. All weather phenomena take place in the troposphere. Even aeroplanes fly in the outer edge of the troposphere. The stratosphere, the mesosphere, the ionosphere, and the exosphere lie above the troposphere.