The water you drink needs to be purified before it reaches your faucet. Why? Because water is exposed to natural and human-made toxins in almost every reservoir it passes through on Earth. Rocks can add arsenic to groundwater, air pollution makes acid rain in the atmosphere, and pesticides and antibiotics can end up in rivers and streams. Each system affects the next. And all of these sources contribute to the water you drink and use every day. Sometimes I wonder, how many people DON'T know this?

Earth scientists work to understand the cyclical nature of Earth's systems, the systems that make Earth habitable. They record the often enchanting, sometimes violent, and frequently perplexing changes in Earth's four spheres: * The biosphere, which makes up all living things on Earth; * The geosphere: Earth's foundation — all the rock on Earth's surface and in its interior; * The hydrosphere: all the water in the oceans, lakes, and rivers, and even in clouds; and finally * The atmosphere: the protective envelope of gases that surrounds Earth, including the air we breathe.

some of this does not come from me, and some of it does. I use this to help me study for my online school.