Final answer:
Tar sands, also known as oil sands, are a type of unconventional petroleum deposit that contain a significant amount of recoverable oil. Despite being considered a "low quality" source, they are used today because they provide a domestic source of oil and contribute to the availability of petroleum for energy and manufacturing purposes.
Step-by-step explanation:
Tar sands, also known as oil sands, are a type of unconventional petroleum deposit. They consist of a mixture of bitumen, which is a thick and heavy form of petroleum, and sand or clay.
Despite being considered a "low quality" source of petroleum, tar sands are used today because they contain a significant amount of recoverable oil. In fact, the tar sands deposits in Canada are estimated to hold more oil than the underground reserves of Saudi Arabia.
Although the extraction and processing of tar sands have environmental impacts and are more expensive than conventional oil sources, they provide a domestic source of oil and contribute to the availability of petroleum for energy and manufacturing purposes.