The document discusses the four main spheres of Earth - the atmosphere, lithosphere, hydrosphere, and biosphere. It provides details about each sphere, including that the atmosphere is made up of 78% nitrogen, 21% oxygen and 1% other gases. It surrounds Earth and provides moderate temperatures and protects the surface from radiation. The lithosphere is the rocky outer shell containing mountains and oceans. The hydrosphere includes all water on Earth like oceans, lakes, ice and groundwater. The biosphere describes where life can exist within the other spheres, including below the Earth's surface.