1.
the gases that surround the earth (close to earth)
2.
the living organisms (plants and animals) that occupy the surface, atmosphere and hydrosphere of the earth.
3.
all the waters on the earth's surface (e.g., rivers, lakes, oceans)
4.
the hard, solid part of the earth (e.g., the soil and rock near the surface)
5.
materials that people put into the environment that can be harmful if there is too much (e.g., smog in air harmful chemicals in water)
6.
the cutting down of forests
7.
a region in the U.S. where agricultural crops died during years when there was too little precipitation in the 1930's and winds blew away soil that was not covered by plants
8.
rainfall that has such a high amount of acid that it harms forests; caused mainly by air that comes from places that burn coal that has high amounts of sulfur.
9.
hazy air that contains smoke or particles or other pollutants.
10.
removal of soil or rock materials by the force of blowing wind or by the force of flowing water
11.
long-term trends in weather conditions (e.g., long-term temperature and precipitation conditions)
12.
changes in temperature and precipitation that occur over a long period of time
13.
sudden growth and expansion of algae (tiny non-flowering plants that grow in water), appearing as a large area of green.
14.
the step-like surfaces that people build on steep hills or mountains to make level pieces of land where they can grow crops with out the soil moving downhill.
15.
to change the physical environment (e.g., to change the vegetation, to change the temperature, to change the shape of the land)
16.
Gases in the Earth's atmosphere trap infra-red heat near the Earth.
17.
The most important greenhouse gas in the Earth's atmosphere; it absorbs infra-red heat and traps it near the Earth's surface
18.
carbon dioxide is released into the air when people burn wood and fossil fuels (e.g. coal, petroleum, natural gas).
