The graph below shows the volume of known petroleum in different regions of the world as estimated in 1997.

Question

Known Petroleum Volume on Earth (1997)

Image courtesy of USGS

The graph shows that most of the known petroleum at the time was located in Region 2, which includes the Middle East and northern Africa.

Based on the large volume of petroleum in Region 2, what kind of activity must have occurred there in the past?
A.
Large amounts of organic matter were buried and then trapped by underground rock formations to create petroleum reservoirs.
B.
Large amounts of carbon dioxide were released into the air and precipitated back down as petroleum.
C.
Flooding in this area resulted in rapid chemical weathering that created petroleum as rocks were broken down.
D.
Mass wasting from northern regions resulted in the deposition of underground petroleum reserves

Answer 1

The correct answer is:

A. Large amounts of organic matter were buried and then trapped by underground rock formations to create petroleum reservoirs.

This option accurately describes the geological processes that lead to the formation of petroleum. Petroleum originates from the decomposition of organic materials (primarily microscopic marine organisms) that are buried under layers of sediment. Over millions of years, heat and pressure transform this organic matter into hydrocarbons, which accumulate in rock formations to form petroleum reservoirs.