Planet Earth | The living planet

 PLANET EARTH

Planet Earth , the living planet formed about 4.5 billion years ago, but it was a very different place then. Its surface was a hot inferno of mostly molten rock, with little or no liquid water and no oxygen in the atmosphere. Since then Earth has developed oceans, continents, an oxygen-rich atmosphere - and life.

UNIQUE PLANET 

Earth is the only place in the Universe known to support life. It is thought that life originated at chemical-rich hot springs on the ocean floors. Eventually, tiny marine life forms evolved that used sunlight as their source of energy. These microbes added oxygen to the atmosphere an essential step for the development of animals.

Inside our planet

Earth's interior has layers Scientists discovered this by studying the paths by which earthquake waves pass through the planet .

Thickness (km)

Crust : 6-90 km (3.7-56 miles)

Mantle : 2,880 km (1,790 miles)

Outer core : 2,255 km (1,400 miles)

Inner core : 1,215 km (755 miles)

Crust 

   Different types of crust make up Earth's land and its ocean floor. Crust is the outermost layer of the planet, it is composed of great variety of igneous,  and Metamorphic and sedimentary rocks. The crust underland is thicker and contains more rock types. 

Mantle 

   This rocky layer is denser than the crust. It forms 16 per cent of the volume of the earth. It is solid, although it can very slowly deform and flow. 

Outer core 

   The only liquid layer. The outer core is mainly iron but also contains some nickel and small amounts of other substances. 

Inner core 

   This is solid. The inner core is mostly iron with some nickel. It has very high temperature of about 5400°C (9,900 F) 

WHAT'S IN A LAYER

   Earth's crust and Mantle are mostly made of minerals called silicates, which are a combination of silicon dioxide and metal oxide. The Mantle is rich in Magnesium -containing silicates, whereas the two different types of Crust have less magnesium and more aluminium and Calcium. The core is dominated by metallic iron. No part of it has ever been brought to the surface, but its composition has been worked out by scientific methods such as studying earthquake waves.

THE OCEANS    

   Earth's surface and atmosphere contain the equivalent of 1.39 billion km^3 (333 million mikes^3) of water. There are regions of deep oceans as well as shallow seas that cover areas around the edges of the continents, these are called continental shelves. Earth's surface has  not always been as dominated by liquid water. In the past, during ice ages when the Polar ice caps were much thicker and more extensive. So much water became looked up in them that sea level was at least 120m. (400ft.) lower than it is today, exposing the continental shelves as dry land. 

   Water world 

  Almost three quarters of Earth's surface is water over 97% of Earth's water is found in oceans. 

EARTH'S ATMOSPHERE    

   Our Earth is surrounded by a huge blanket of air called atmosphere. The atmosphere of Earth is made up of several different gases. 

                                  

Nitrogen - 78%

  It is the most plentiful gas in the air. This gas can be ''fixed'' in the soil, as well as loose in the atmosphere. Plants need nitrogen from the soil to survive.

Oxygen - 21%

   Oxygen is the second most plentiful gas in the air. It is essential for animals to breath, Oxygen was absent until microbes evolved that could use sunlight to turn carbon dioxide and water into carbohydrates, releasing oxygen.

Argon - 0.9%

   An inert gas (one that doesn't react with other substances) 

Other - 0.1%   

These include Carbon Dioxide (CO2), which is abundant, but is now mostly incorporated into materials such as Limestone rock. 

CONTINENTAL DRIFT     

  Over millions of years tectonic plates have moved shifting around the continents on Earth's surface. Chunks of continents split away and push into each other, creating new land masses and moving the oceans in a process called 'continental drift'. 

PLATE MOVEMENT        

   The continents get rearranged because they are carried along as parts of moving plates. This process has been going on for billions of years, and is thought to be caused by slow, heat driven and movements in Earth's Mantle.

Yearly Shift 

    Plates typically move at a rate of 2.5 cm in a year and Some move faster - up to 10 cm in a year.

A SPINNING PLANET 

   Due to the gravity of the earth, it is pulled into the shape of a sphere, but its rotation makes it bulges slightly. This means its diameter at the equator is 41 kilometre more than the distance between its poles.

 

Not quite round

   The giant Jupiter spins even faster, than earth and its equatorial diameter is 7% greater than its polar diameter.

MAGNETIC EARTH

   The earth magnetic field is the magnetic field that surrounds the Earth. Because Earth's outer core is liquid, the planets rotation stirs it into motion. This motion causes electric currents to develop in the liquid iron itself. Any electric current pattern creates a magnetic field. In earth case, the field is similar to what would be produced by a large magnet bar inside the planet. The field protects Earth from damage by harmful, energetic particles that come from the Sun.

The magnetic field

   The magnetic pole do not collide exactly with the Geographic Poles, and they gradually change position over time.

LOOKING AT THE EARTH        

    Our planet is far from smooth, it's continent and ocean floors are scattered and pitted with marks caused by plate movement. Earth's  place in space also affects its shape, as constantly spinning makes it bulge out around the middle instead of forming a sphere. 

Spinning creates a magnetic safety field around the planet. 

Mountains make up about 1.5th the earth's landscape.

 EARTH'S SURFACE  

   The solid surface of the Earth ranges from about 10,900 m (35,750 ft) below sea level in the Challenger Deep part of the Pacific's Mariana trench to 8,848m (29,029ft )above sea level at the summit of Everest, which may be rising at about 4 mm (0.16 inches) per year. The surface of most, land areas is less than 500 m (1,650 ft) above sea level.