The four main systems of the Earth are

The four main systems of the Earth are the rocks, water, air and life. Mountains, volcanoes, hills, plateaus, sand, pebbles represent the rocks. These are where most of the plants and vegetation takes place. Also, these are where most of the organisms that lives on land take place. Oceans, rivers, ponds, lakes, waterfalls represent the water. These are where most of the organisms that lives on water is located. It is said that earth consists of 70% of water and the rest are land. Air is the reason why all of the microorganisms living on earth are alive because of its composition, 21% oxygen and 79% nitrogen. And life, the organisms that dwells on earth.