Within the boundary of earth is a collection of four interdependent parts known as ‘spheres’. These four parts include the Lithosphere, Hydrosphere, Atmosphere and Biosphere.

The Lithosphere

The Lithosphere is made up of the crust and upper mantle of the Earth. The Lithosphere can be broken into several Continental and Oceanic Tectonic Plates. These are known as Lithospheric plates. Continental and Oceanic Tectonic Plates differ within their size and composition. The effect of the different densities of lithospheric crust can be seen in the different average elevations of continental and oceanic crust.

Beneath the Lithosphere is the mantle which is considered to be the most voluminous of layers that make up the planet with an estimated depth of around 2,900 Kilometers.

Continental crust is often found to be made of granitic mixtures of Volcanic, Sedimentary and Granite rocks. As seen in the diagram, the Continental crust is denser than Oceanic crust and is generally older and more complex. Its estimated density approximates at 2.7 grams per cubic Centimeter with a thickness of up to 75 Kilometers. Continental crust has greater buoyancy and is able to float much higher in the mantle.

Ocean crust is generally found to be lighter in weight in comparison to Continental crust. The ocean basin consists of sediments which overlap basaltic rock. Oceanic crust rocks are composed mainly silicon, oxygen and magnesium. The estimated density of Oceanic composition is measured to be about 2.9 grams per cubic Centimeter with the crust being 6 to 7 Kilometers thick.

The Hydrosphere

The Hydrosphere is basically all the water on Earth from both above and under the ground. Water in the Hydrosphere can be found in all solid, gaseous and liquid forms such as ice, vapor and water.

As the diagram shows, the Hydrosphere works in a cycle. Liquid water from lakes and oceans evaporate into vapour forming clouds and sometimes fog in the atmosphere, vapor precipitates into either a solid (ice) or liquid (water) form where ice or snow can melt into liquid once more where the cycle repeats.

The Atmosphere

The Atmosphere is generally the layer of gases that surround Earth which are held in place by gravity. 78% of the atmosphere is consists of nitrogen, 21% consists of oxygen while the other 1% can be a mixture of carbon dioxide, methane, ozone and other gases. The Atmosphere can be broken down into five layers depending on the altitude from Earth and the temperature. As you shift further away from earth the atmospheric pressure decreases. The five parts of the atmosphere include the Thermosphere (furthest from Earth) which has an altitude of approximately 21.3 Kilometers and a temperature of -55.2 degrees, Mesosphere, Stratosphere and the Troposphere (closest to Earth) which has an altitude of 1.5 Kilometers and a temperature of 5.1 degrees .

The Biosphere

The Biosphere is a combination of all ecosystems on Earth. The Biosphere stretches as far as the Hydrosphere, Atmosphere and Lithosphere. Organisms included in the Biosphere are found in water, on land and in the sky (ecosystem) creating species diversity. The Biosphere is considered to be the center spheres.

When it comes down to the four spheres of the Earth’s global system, they are all dependent on one another. For example, trees (biosphere) depend on water (hydrosphere) to run through soil (lithosphere) in order to live so that they can produce oxygen (atmosphere) in order for other organisms to survive. The spheres are so closely connected that a change in one sphere will often result in change in one or more of the other spheres (Earth System Science, 2004).

The Nitrogen Cycle

All plants and animals need nitrogen to make amino acids, proteins and DNA, but the Nitrogen in the atmosphere is not in a form they can use (Earth System Science, 2004). This is where the Nitrogen cycle occurs. The Nitrogen Cycle makes it possible for organisms to utilize the