Explain the interrelationships between the four main spheres of the earth.
The four main systems or spheres of Earth include the lithosphere (or geosphere), hydrosphere, atmosphere and biosphere. The lithosphere consists of Earth's crust, mantle and core, mountains, rocks, etc. The hydrosphere consists of all the water on Earth, including rivers, lakes, ponds, glaciers, groundwater, etc. The atmosphere consists of all the gases including oxygen, nitrogen, carbon dioxide, etc. The biosphere is made up of all the life on Earth, including plants, animals, etc.
All these spheres are in constant interaction with each other. A great example is the global biogeochemical cycles, such as the carbon cycle. Carbon dioxide from the atmosphere is used by plants (biosphere) for photosynthesis and is also incorporated into our bodies. Respiration releases carbon dioxide back into the atmosphere. Carbon dioxide is also fixed as carbonates in the rocks, especially by our oceans.
One can also think of natural events such as volcanic eruptions as an interaction between the spheres. Volcanic eruptions release gases into the atmosphere. Molten lava, when it solidifies, forms more rocks. The eruption also kills organisms and plants.
One can think of a number of other processes/events (such as acid rain, photosynthesis, eutrophication, etc.) that involves interactions between these spheres.
Hope this helps.