Why are dams, bridges, rock quarries, and oil wells considered land in economics?
I would suggest that you check with your instructor on this, because bridges, dams, and at least part of oil wells would not be considered land by any economists I am familiar with. In the two links below, you can see that “land” is generally used as a term for anything that is part of the natural world and has not been improved by human beings. As a third example, the text from which I typically teach economics, Survey of Economics, by Irvin B. Tucker, defines land as
…any natural resource provided by nature.
Thus, land, in economic terms, cannot be something that is made by human beings.
A quarry would generally be seen as land. The rocks in the quarry are provided by nature and are not yet improved by human beings. The oil in an oil well would also be considered land, but the infrastructure used to get the oil out of the well (all of the pipes and such that make up the well) would not be considered land. They would be considered capital because they are made by human beings and used to produce other goods.
Bridges and dams cannot be considered land in any way. These are things that did not exist before people made them. They are not a “natural resource” and cannot be considered to be “land.”
Please check with your instructor to see if they are using a different definition for land than the ones in the links or in the text I quoted.