Passage III
Forest fires require oxygen (O2) to burn. Figure 1 shows the number of paleowildfires (large forest fires known from the rock record) for each 10-million-year interval of the Mesozoic era (250-65 million years ago, mya). Figure 1 also shows a model of the percent O2 by volume (%O2 ) in Earth's atmosphere from 250 mya to 70 mya.
To study how %O2 affects burning, scientists attempted to ignite 7 samples of each of 4 different materials, 1 sample at a time, in a chamber. For each set of samples of the same material, the initial %O2 in the chamber ranged from 12% to 18%. Figure 2 shows, for each sample that ignited, the duration of the sample's flame.
Figures adapted from C. M. Belcher and J. C. McElwain, "Limits for Combustion in Low O2, Redefine Paleoatmospheric Predictions for the Mesozoic." ©2008 by American Association for the Advancement of Science.
16. A scientist claimed that paleowildfires could only have occurred when the %O2 was higher than 15. For which of the following time intervals during the Mesozoic era are the data in Figure 1 inconsistent with this claim?
Your Answer is
Correct Answer is G
Explanation
Look at figure 1 to locate the four intervals, only the oxygen between 180-160 is less than 15%, so this time period does not meet the claim of the title