Einstein Science Reporting for Kids
[ E-mail ]

Contact: Science Press Package
American Association for the Advancement of Science

A different kind of cave treasure

A cave explorer admires the towering 'Night Watchmen' stalagmites found in a dry fossil passage of Whiterock Cave in Gunung Mulu National Park, Malaysia. Tropical stalagmites are invaluable climate archives as they record changes in rainfall over hundreds of thousands of years.
[Image Robbie Shone / www.shonephotography.com]

What do you think the scientists who explored the amazing caves in these pictures were looking for? Bats? Skeletons? Pirate treasure? Actually, it was the stalagmites that they were after, because these spiky formations contain important chemical clues to ancient climate.

Anna Meckler of the California Institute of Technology and the Swiss Federal Institute of Technology Zurich and colleagues, have analyzed the climate history recorded in stalagmites from three different caves in Gunung Mulu and Gunung Buda National Parks in northern Borneo.

One of the largest islands in the world, Borneo is in the tropical west Pacific, south of the Asian continent and north of Australia.

Dr. Meckler's team wanted to learn more about a time period called the Pleistocene epoch, which included a series of ice ages, interspersed with warmer periods called "interglacials."

In the lab, the stalagmites are cut open lengthwise and sampled along their main growth axis by drilling out small amounts of calcite powders. The powders are then analyzed for their chemical composition, which reflects the composition of the drip water at the time the calcite was formed. In the caves of Borneo, changes in drip water composition can be interpreted as past changes in precipitation. Separate samples taken for radiometric dating allow assigning a time to each layer in the stalagmite.
[Image courtesy of Dr. Nele Meckler]

In particular, the researchers wanted to know how climate changed in the tropics, which brings us back to the stalagmites from Borneo. Stalagmites form gradually as dripping water hits a spot on the cave floor and leaves behind a tiny mineral deposit. By studying those minerals scientists can figure out how fresh or salty the dripping water was, and thus how rainy (or snowy) the climate was at certain points in time.

When Dr. Meckler and her colleagues analyzed the chemistry of their stalagmite samples, which spanned a time period from about 550,000 to 200,000 years ago, they found that precipitation levels were pretty similar during all four of the interglacials they studied but varied during the glacial periods. These findings should help research piece together a whole picture of how the high latitudes and the tropics respond during climate change events.

Scientists hope that if they can understand why and how past global changes occurred, they'll have a better sense of how climate might continue to change in the future. The research is being published online by the journal Science, at the ScienceExpress Web site, on 3 May.