Cave Dates and Climate Estimates May Be Off
The steady drip, drip, drip of water from stalactites should provide a way to calculate the age of cave formations, right? Don’t be too sure. A scientist at Florida State found that calcite deposition is a function of how the cave “breathes,” reported New Scientist. This finding “pours doubt on ancient climate records derived from these structures.”
Climate researchers have no way of directly recording temperature for dates before about 1850. They use “proxy measurements” from tree rings, ice cores, cave formations and written descriptions. Tree ring measurements have come under fire lately with the Climategate scandal. It appears the use of cave formations for estimating prehistoric climate records is now subject to question. “Some records of ancient rainfall may be skewed, as estimates based on stalactite formation assume year-round mineral deposition,” the article said.
The point to remember here, without getting into details about the extent of possible misinterpretation, is that all dating methods make assumptions. A geologist sees the steady dripping from a stalactite, measures the calcite deposition on the stalagmite below, calculates the deposition as a function of drip rate, and then extrapolates the measurements hundreds of thousands of years back in time. Can any geologist possibly know all the factors that could affect the deposition rate? This article pointed out one, but there could be many others.
The estimation of ancient climate is just as fraught with assumptions. If the geologist establishes a plausibly reliable deposition rate under current conditions, he or she might infer from slight differences in composition in a cross-section of a stalactite how the climate cooled or warmed over time. But some factors might not correlate together. They could counteract one another in all kinds of ways. To show this story is not an isolated case in Florida, recall the 01/19/2006 finding in Texas about kinetic factors including the angle of the glass plate a scientist might use to collect data, or the presence of a warm human body in the cave. South African scientists, frustrated with anomalous measurements, concluded that “the constant speleothem growth rate we assume is simplistic” (10/12/2004, bullet 4).
The unknown factors are the most worrisome. This story points out that theory-destroying factors no one ever thought about, like cave bears, could be lurking in dark passages.