Everything in Earth's system can be placed into one of four major subsystems: land, water, living things, or air. ... Beneath that layer lies a very thin, solid crust of oxygen and silicon. ... The atmosphere contains all the air in Earth's system. ... When air temperature in the lower portion of this sphere changes, weather occurs. As air in the lower atmosphere is heated or cooled, it moves around the planet. ...

• Word Count: 1504
• Approx Pages: 6
• Grade Level: High School

I quickly get out of those ridiculous clothes and change into my military issued uniform. ... Now they never told you where you were going until you were about an hour into the flight. ... Finally a tall pale thin guy with big bags under his eyes, probably from working the night shift, enters the room and notifies us that we can board the aircraft. ... Seeing the tired looks on everyone's faces made it pretty obvious that once in the air nobody would last too long. ... Also the air conditioning had turned on. ...

• Word Count: 2013
• Approx Pages: 8
• Grade Level: High School

These regions are arid because they are occupied by dry, subsiding air for most of the year. Moist air moving into Africa, mainly from the South Atlantic and the Indian Ocean, is monsoonal in character. The humid, unstable air moves inland in summer. ... It has only a thin layer of top soil which is the source of nutrients for the vegetation. ... The fires cause a large release of Carbon into the atmosphere. ...

• Word Count: 2357
• Approx Pages: 9
• Has Bibliography
• Grade Level: High School

It comes in many forms, such as air pollution, noise pollution, water pollution, and many others. ... When it rains, the DDT can be washed into a nearby stream, which feeds into a big river and then into the ocean. ... There were more eggs in the nest than usual, and the eggs also had thin shells. ...

• Word Count: 2382
• Approx Pages: 10
• Has Bibliography
• Grade Level: High School