Which of the following best explains why Scientist 2 mentions nickel?
About 250 million years ago, over 90 percent of all species on Earth went extinct in an event called the "Great Dying".
Significant evidence links the time of the Great Dying to the time of a massive increase in the Earth's average
temperature caused by a runaway greenhouse effect. Two competing theories seek to explain what may have caused
the runaway greenhouse effect.
The mass extinction at the Permian-Triasic boundary occurred about 250 million years ago and was initiated by a truly
massive volcano erupting in what is now Siberia. The volcano covered an area about the size of the United States with
lava, to a depth of about 5 kilometers (3 miles). While this caused a significant change in the Earth's atmosphere by
releasing sulfur and other compounds in great quantities, the eruption alone is not sufficient to explain the global
Fortunately, there is ample evidence in ocean sediments that the lava flows caused vast quantities of coal to ignite,
releasing tremendous amounts of carbon dioxide. The ocean sediments of this time period show significant quantities
of coal ash. This coal ash not only indicates the burning of massive amounts of coal, but would also have contributed
significantly to the acidification of the oceans. It is clear that the emission from the volcanic eruptions, combined with
the burning of these massive coal deposits, led to the dramatic temperature increase which resulted in the Great Dying.
The amount of sulfur and carbon dioxide released by the Siberian volcano eruptions and coal deposits is not enough to
explain the massive worldwide change in climate that caused the Great Dying. It is probable that another critical factor
pushed the global carbon cycle over the edge. There is significant evidence that a newly evolved microbe was a key
element in the global climate change that led to the Great Dying.
Genetic analysis shows that the microbe Methanosarcina evolved around the time of the Great Dying. This
microbe had developed the ability to consume organic materials and convert them to methane. Methane is an
extremely potent greenhouse gas that reacts with oxygen in the atmosphere to produce carbon dioxide. The
Methanosarcina microbe relies on an enzyme that contains nickel atoms to metabolize the organic material.
Analysis of ocean sediment shows the amount of nickel increased after the volcanic eruptions. It is likely that the
volcanic eruptions expelled significant amounts of nickel into the oceans and caused a dramatic increase in the amount
of Methanosarcina. This in turn led to an increase in methane and carbon dioxide in the atmosphere, and
thus caused the dramatic global temperature increase that caused the Great Dying.