Trans-Alaska Pipeline and Permafrost

Photo showing a section of the Trans-Alaska Pipeline, which carries crude oil. The pipeline had to be uniquely constructed due to the cold conditions and permafrost that surrounds much of the line. As such, the majority of the line is above ground so as not to cause thawing of the permafrost, which might in turn cause sinking. Permafrost is soil that has been frozen for a length of time and doesn't thaw as the seasons change.