Energy production/acid rain<span>, nuclear power/waste, </span>air pollution<span>/climate, heavy metals, pesticides, water </span>pollution<span>, solid waste, and unforeseen accidents.</span>
The main difference between asteroids<span> and </span>comets<span> is their composition, as in, what they are made of. </span>Asteroids<span> are made up of metals and rocky material, while </span>comets<span>are made up of ice, dust and rocky material. Both </span>asteroids<span> and </span>comets<span> were formed early in the history of the solar system about 4.5 billion years ago.</span>
Because many rivers run swiftly down int mountains.
Hope that helps