STALAGMITES look like ice cream cones after they?ve fallen?ice cream first?onto the sidewalk. They form through millennia of deposits from calcite-laden water dripping onto the cave floor.

Like the concentric rings on a tree trunk or the layers of ice drilled from the polar regions, the layers of deposits on a stalagmite can be studied to learn about weather patterns from times gone by. Researchers from the University of Wisconsin, the Geological Survey of Israel and The Hebrew University have been analyzing the chemical signatures of the stalagmite layers in an Israeli cave to learn the role climate plays in shaping history.

?It looks sort of like tree rings in cross-section,? University of Wisconsin-Madison geologist and study lead author Ian Orland said in a statement. ?You have many concentric rings and you can analyze across these rings, but instead of looking at the ring widths, we?re looking at the geochemical impurities of each ring.?

Climate change

Their findings suggest that climate change in the eastern Mediterranean region that today includes Israel, Syria and Iraq contributed to the decline of the Roman Empire.

The work by Orland and his colleagues is currently available online in the journal Quaternary Research and is expected to appear in a future issue.

At the height of its power, the Roman Empire surrounded the Mediterranean Sea and ranged from Spain to England in the northwest, to Syria in the east and to Egypt and northern Africa in the south. To get an idea of the land mass involved, consider that 20 countries the size of the Philippines could fit within the Empire?s borders.

The Roman Empire lasted some 400 years before the western half fell in the fifth century AD. The eastern half of the Empire, later known as the Byzantine Empire, lasted for several more centuries.

Several factors have been blamed for the Empire?s decline, including constant attacks at the borders starting around the third century AD and political unrest in Rome itself.

In their study, Orland and his colleagues propose that climate change on the eastern border of the Empire was also a factor. The agricultural economy in the region was affected by low crop yields due to decreasing rainfall.

?These results suggest a drying of regional climate that coincides with the decline of the Roman and Byzantine Empires in the [eastern Mediterranean] region,? the researchers wrote in their study.

Orland and his colleagues based their findings on an analysis of stalagmites growing in the 185,000-year-old Soreq Cave in central Israel, near Jerusalem and roughly between the Mediterranean Sea and the Dead Sea. Chemical analyses of stalagmite layers equivalent to periods ranging from a decade to a century provided the researchers with information such as the rainfall amounts and cave-air temperatures for a timeline stretching from roughly 200 BC to 1100 AD.

An analysis of the stalagmite rings showed that the rainfall in the region decreased over time between 100 AD and 700 AD. The data complement results from other studies that show the water level in the Dead Sea dropped by a minimum of 10-15 meters (33-49 feet) during the same time period.

The researchers wrote that the analysis also indicates ?there were always dry years, but the number of wet periods, which might have aided crop yields, decreased.?

Demographic disaster

Climate change has also been noted as a factor in the decline of the Mayan civilization in Central America, an event which Nasa (National Aeronautics and Space Administration) archeologist Tom Sever once referred to as the ?the greatest demographic disaster in human prehistory.?

Earlier this year, researchers from the US space agency presented information suggesting the Mayans might have induced drought conditions by destroying the wetlands in their area for farmland to feed the large urban populations.

E-mail the author at massie@massie.com.