Spheres Inside of Spheres

Essay by BritnyHigh School, 10th grade October 2006

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The Earth, the planet on which we live, is very complex, although looks like a simple planet. It is made up of three main features: land, air, and water; land on earth is called the lithosphere; the hydrosphere is the Earth's water; and the atmosphere is the air we breathe.

The atmosphere, a mixture of gases in the air, took 4.5 billion years to evolve. Methane and ammonia were deadly gases common in ancient atmospheres. Chemical reactions on earth caused the breakdown of theses gases into nitrogen, hydrogen, and carbon dioxide. The atmosphere's first mixture was made up of volcanic matter. Condensation (when water vapor changes back into liquid) occurred, and a lot of volcanic water vaporized to fill the first oceans. As time went on, photosynthesis (a chemical process plants use light to make oxygen) made it possible for new marine life capable of respiration. Eventually, about 570 million years ago, the oxygen levels were high enough for marine life to survive.

The atmosphere had enough oxygen for air-breathing land animal about 400 million years ago. The four major gases found in the atmosphere today are nitrogen, oxygen, carbon dioxide, and water vapor.

The hydrosphere is a layer of water in the form of oceans, seas, lakes, and rivers, which cover about 70.8 percent of the earth. The hydrosphere is the name for the layer water on Earth. The water on Earth is a distinctive feature that distinguishes our planet from others in the solar system. No liquid water can be located anywhere else besides it. Because of the Earth's mass, chemical composition, atmosphere, and the right distance from the Sun the conditions let water to exist primarily as a liquid. The assortment temperatures and pressures of the planet allow water to exist in all three states: solid, liquid,