One example of earth material is oil shale, which is found in some areas of Canada.

One example of "earth material" is oil shale, which is found in some areas of Canada. A controversial proposal involves mining this shale, and transporting it via a proposed pipeline through the US to the Gulf of Mexico. Do a bit of research into what oil shale is, and how it's extracted. Then briefly explain the controversy behind the Keystone Pipeline, and how you feel about it.