The Earth consists of layers, including a solid iron inner core, liquid outer core, mantle, and thin crust. Movement in the crust causes earthquakes and volcanoes. The crust is broken into tectonic plates that move and occasionally cause pressure buildup released by quakes. Air contains nitrogen, oxygen, and other gases essential for life. Most water is in the oceans, with freshwater in glaciers and underground. Wind circulates due to hot air rising and cold air sinking, influencing the water cycle.