Passage

Crude mineral oil comes out of the earth as a thick brown or black liquid with a strong smell. It is a complex mixture of many different substances, each with its own individual qualities. Most of them are combinations of hydrogen and carbon in varying proportions. Such hydrocarbons are also found in other forms such as bitumen, asphalt, and natural gas. Mineral oil originates from the carcasses of tiny animals and plants that lived in the sea. Over millions of years, these dead creatures formed large deposits under the sea-bed; and ocean currents covered them with a blanket of sand and silt. As this material hardened, it became sedimentary rock and effectively shut out the oxygen, preventing the complete decomposition of the marine deposits underneath. The layers of sedimentary rock became thicker and heavier. Their pressure produced heat, which transformed the tiny carcasses into crude oil in a process that is still going on today.

QUESTION

CSAT

Easy

Comprehension

Prelims 2013

Mineral oil deposits under the sea do not get completely decomposed because they:

Select an option to attempt

Explanation

Statement 1 is incorrect. While ocean currents may affect the movement of sediments, they do not prevent the complete decomposition of mineral oil deposits. The key factor in the preservation of these deposits is the lack of oxygen, not the washing effect of currents.

Statement 2 is correct. As the deposits of marine organisms become buried under layers of sediment, they eventually form sedimentary rock. The layers of rock prevent oxygen from reaching the carcasses, which in turn stops complete decomposition and allows the formation of crude oil.

Statement 3 is incorrect. While mineral oil is composed of hydrocarbons (a mixture of hydrogen and carbon), the inability of the deposits to decompose is primarily due to the lack of oxygen caused by the rock layers above, not the chemical composition of the oil itself.

Statement 4 is incorrect. The saline conditions alone do not prevent the decomposition of the marine organisms. The critical factor is the lack of oxygen as the organic material gets buried under layers of sediment.