A system is a collection of interdependent features that all work together to achieve something. In the earth, these features are the atmosphere (air), the biosphere (life), the hydrosphere (water) and the lithosphere (rock), they are all working together to achieve equilibrium. A lot of the things in each sphere interlink and connect with each other, so if something changes in one of them, it will affect at least one of the other spheres.
Since all of the spheres are interlinked, it is hard to define each of them separately because they need another part of the system to be able to work, and they will also affect another part of the system.
The atmosphere is divided into four main sections. From the ground up, there is the troposphere (3/4 of our atmosphere is here), the stratosphere (where there is no weather and is home to the ozone layer), the mesosphere (where meteors burn up), and the thermosphere (where space shuttles orbit the earth). The atmosphere around our earth absorbs heat from the sun, which makes our planet habitable. As we travel through our atmosphere, away from the earth, the temperature will decrease. The atmosphere controls the weather on the planet by transporting hot and cold air around the earth in an attempt to reach equilibrium; if this didn’t happen, we would have extreme high and low temperatures on the earth. This links into the hydrosphere and the water cycle because clouds are formed when water is evaporated by heat. When this eventually turns into rain, it will have an effect on some of the earth’s other spheres.
The lithosphere is the planets cold, hard and solid rock, as well as the mantle under the earth’s crust. Parts of the atmosphere can affect the lithosphere. For example, the force of the wind can erode rocks, move the sediment, and then deposit it. If the sediment gets deposited into the sea, the plate tectonics mean that at subductive plate boundaries, the compacted sediment would get melted and turned into mantle under the crust. The mantle would then recreate land as volcanic islands, mountains, or ridges at the plate boundary. These processes all acting together shows the earth trying to reach equilibrium, because the land has been eroded, but over time, the land will be recreated because of the processes the earth carries out in all of its spheres.
The hydrosphere (the planets solid, liquid and gaseous water) is closely linked with the same processes as above. The water in the rivers and the sea, and also rainfall, will erode the land, and it will eventually get recreated as the earth tries to reach equilibrium. There are many processes that act within the sphere, like erosion, transportation and deposition, so there are a lot more factors that contribute to the system within each of the