Seams, Seams, Seams
We obtain coal from underground seams. A seam is a layer of ore
or coal that is thick enough to be profitably mined. We obtain
the coal in one of two ways:
- By surface mining, which involves removing the soil and rock
above the coal seam so that it can be removed from the surface.
- By underground mining, which involves digging shafts to access
Oil and gas are also found underground, but as fluids in layers
of porous rock. This mixture of oil and gas is known as
petroleum, which we access by drilling wells.
The liquid part of petroleum is called "crude oil," or "oil" for
The gaseous portion is called "natural gas," or "gas" for
The word "petroleum" comes from the Latin words petra and
oleum, meaning "rock" and "oil." People
originally used the phrase
"rock oil" to distinguish it from vegetable oil and animal oil.