By David Shiga
Using altitude-dependent differences in fossil leaves, geologists have developed a tool that they say can track land elevations over geologic epochs. The scientists plan to use the new technique to better chronicle the rise and fall of mountain ranges.
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Trees’ leaves breathe in carbon dioxide through tiny pores, called stomata, that can be seen with a microscope in both modern and fossilized samples. At higher altitudes, the leaves grow with more tightly packed pores to compensate for the thinner air. Jennifer C. McElwain of the Field Museum in Chicago has taken advantage of this anatomical adaptation to turn fossil leaves into a measure of ancient altitudes. She details the strategy in the December Geology.