The movement of material due to differences in density is called

If we were talking about placer gold deposits, the placer gold settles out by gravity from the stream or river where it loses energy like on the upstream side of sand bars since it has a high density so if the current slows down it settles out quickly compared to the very low density say clay particles which are easily washed further down the river. 

Increasing the release of greenhouse gases and pollution

Check -it can you examine advantages and drawbacks to possible solutions.check-it can you consider options to solve a problem.check-it can you persuade an audience to support a proposal.check-it can you identify the cause of a problem.