Large area of flat land at the top of a mountain
The coldest climatic zone , located between 66 1\2 degrees north and south latitude and the poles
The introduction of substances into an environment that produce harmful changes in the environment
Another name for the Greenwich Meridian
Materials from the earth that can be replaced by natural cycles
Put aside or withheld for future need
The earth's complete movement around the sun
The scale used to measure the strength of earthquakes
A stream of fresh water , flowing over land in definite channel to the sea
A complete turn of the earth on its axis
Rough irregular tract of land
Objects which revolve around individual planets. For example earth's moon is a natural satellite
A body of salt water that is smaller than an ocean
Waves that travel through the ground from an earthquake
An instrument that measures and records the force and directions of earthquake