Since the early 1920s, most petroleum geologists have favored a biogenic theory for the formation of oil. According to this theory, organic matter became buried in sediments, and subsequent conditions of temperature and pressure over time transformed it into oil.
Since 1979 an opposing abiogenic theory about the origin of oil has been promulgated. According to this theory, what is now oil began as hydrocarbon compounds within the earth’s mantle (the region between the core and the crust) during the formation of the earth. Oil was created when gasses rich in methane, the lightest of the hydrocarbons, rose from the mantle through fractures and faults in the crust, carrying a significant amount of heavier hydrocarbons with them. As the gases encountered intermittent drops in pressure, the heavier hydrocarbons condensed, forming oil, and were deposited in reservoirs throughout the crust. Rock regions deformed by motions of the crustal plates provided the conduits and fractures necessary for the gases to rise through the crust.
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Opponents of the abiogenic theory charge that hydrocarbons could not exist in the mantle, because high temperatures would destroy or break them down. Advocates of the theory, however, point out that other types of carbon exist in the mantle: unoxidized carbon must exist there, because diamonds are formed within the mantle before being brought to the surface by eruptive processes. Proponents of the abiogenic theory also point to recent experimental work that suggests that the higher pressures within the mantle tend to offset the higher temperatures, allowing hydrocarbons, like unoxidized carbon, to continue to exist in the mantle.
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If the abiogenic theory is correct, vast undiscovered reservoirs of oil and gas—undiscovered because the biogenic model precludes their existence—may in actuality exist. One company owned by the Swedish government has found the abiogenic theory so persuasive that it has started exploratory drilling for gas or oil in a granite formation called the Siljan Ring—not the best place to look for gas or oil if one believes they are derived from organic compounds, because granite forms from magma (molten rock) and contains no organic sediments. The ring was formed about 360 million years ago when a large meteorite hit the 600-million-year-old granite that forms the base of the continental crust. The impact fractured the granite, and the Swedes believe that if oil comes from the mantle, it could have risen with methane gas through this now permeable rock. Fueling their optimism further is the fact that prior to the start of drilling, methane gas had been detected rising through the granite.
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1. Which one of the following statements best expresses the main idea of the passage?
(A) Although the new abiogenic theory about the origin of oil is derived from the conventional biogenic theory, it suggests new types of locations for oil drilling.
(B) The small number of drilling companies that have responded to the new abiogenic theory about the origin of oil reflects the minimal level of acceptance the theory has met with in the scientific community.
(C) Although the new abiogenic theory about the origin of oil fails to explain several enigmas about oil reservoirs, it is superior to the conventional biogenic theory.
(D) Although it has yet to receive either support or refutation by data gathered from a drilling project, the new abiogenic theory about the origin of oil offers a plausible alternative to the conventional biogenic theory.
(E) Having answered objections about higher pressures in the earth’s core, proponents of the new abiogenic theory have gained broad acceptance for their theory in the scientific community.
2. Which one of the following best describes the function of the third paragraph?
(A) It presents a view opposed to a theory and points out an internal contradiction in that opposing view.
(B) It describes a criticism of a theory and provides countervailing evidence to the criticism.
(C) It identifies a conflict between two views of a theory and revises both views.
(D) It explains an argument against a theory and shows it to be a valid criticism.
(E) It points out the correspondence between an argument against one theory and arguments against similar theories.
3. The passage suggests that the opponents of the abiogenic theory mentioned in the third paragraph would most probably agree with which one of the following statements?
(A) The formation of oil does not involve the condensation of hydrocarbons released from the earth’s mantle.
(B) Large oil reserves are often found in locations that contain small amounts of organic matter.
(C) The eruptive processes by which diamonds are brought to the earth’s surface are similar to those that aid in the formation of oil.
(D) Motions of the crustal plates often create the pressure necessary to transform organic matter into oil.
(E) The largest known oil reserves may have resulted from organic matter combining with heavier hydrocarbons carried by methane gas.
4. Which one of the following is most analogous to the situation described in the final paragraph?
(A) A new theory about the annual cycles of breeding and migration of the monarch butterfly has led scientists to look for similar patterns in other butterfly species.
(B) A new theory about the stage at which a star collapses into a black hole has led astronomers to search for evidence of black holes in parts of the universe where they had not previously searched.
(C) A new theory about how the emission of sulfur dioxide during coal-burning can be reduced has led several companies to develop desulfurization systems.
(D) A new theory about photosynthesis has convinced a research team to explore in new ways the various functions of the cell membrane in plant cells.
(E) A new theory about the distribution of metals in rock formations has convinced a silver-mining company to keep different types of records of its operations.
5. According to the passage all of the following are true of the Siljan Ring EXCEPT:
(A) It was formed from magma.
(B) It does not contain organic sediments.
(C) Its ring shape existed 500 million years ago.
(D) Methane gas has been detected rising through it.
(E) It was shaped from the granite that makes up the base of the continental crust.
Answers: D,B,A,B,C
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P1
In paragraph one we are given that the biogenic theory has explained the formation of oil since the 1920's. According to this theory the organic compounds preset in the earth's sediments were converted in oil thanks to changes in temperature and pressure.
Brief summary: The biogenic theory
P2
In paragraph 2 we are given that from 1979 a new theory was formulated: the biogenic theory. The supporters of this theory claim that il was formed by hydrocarbons present in the earth's mantle. Such hydrocarbons were subjected to drops in pressure and were subsequently converted in oil.
Brief summary: The Abiogenic theory
P3
Opponents of the Abiogenic theory claim that hydrocarbons…