Will we ever have another Ice Age?
Toni Markowicz and Tyler Carpenter, both 11 years old and entering the sixth grade at Gurnee's Viking Middle School, had questions about the Ice Age.
"What did it look like during the Ice Age? What causes the Ice Age? Are we ever going to have another Ice Age?"
There have been about 10 ice age periods - periods when glaciers have advanced and retreated - in the past 2 million years, according to Bill Burger, botanist at Chicago's Field Museum.
"They have averaged around 100,000 years long. The 'interglacial.' warm periods between ice ages have been much shorter - around 10,000 to 20,000 years," Burger said.
The last Ice Age, which ended nearly 15,000 years ago, was characterized by ice sheets 10,000 feet thick that stretched across the northern sections of North America, Europe and western Asia. Summer's hot sun was not hot enough to penetrate the ice sheets so they remained intact all year long. "The last ice sheet extended south of the Great Lakes in North America and probably covered much of Northern Europe," Burger said.
What did it look like during the Ice Age? Chicago was more like Siberia, with thick ice covering nearly everything. Tundra and conifer woods appeared in areas that were not blanketed in ice.
Lots of animals lived here during the Ice Age. Some animals that didn't make it through the warming periods were short-faced bears, saber-toothed cats and dire wolves. A few that adapted to the warmer climate and still live in the area are jaguars, porcupines and the northern grasshopper mouse.
"The Amazon was green and moist but cooler. Deserts may have been smaller," Burger said.
Why do these glacial periods occur? The Earth's orbit and axis change ever so slightly over thousand-year cycles, and these changes might have contributed to the cooling cycles. "Changes in how circular the Earth's orbit is, changes in the angle of the Earth's axis to the plane of its orbit, and changes in what time of the year the Earth is closest to the Sun all vary over thousands of years," Burger said. "These cycles seem to have interacted and played a part in determining glacial cycles over the last 2 million years."
When's the next ice age going to get here?
"Theoretically, we should be looking toward another cold glacial cycle coming our way, as the interglacial we're in now is around 15,000 years old. However, burning thousands of tons of fossil fuel every second means we are adding carbon dioxide to our atmosphere at an impressive rate," Burger said. This gas acts like a blanket, permitting the Sun's shortwave radiation to penetrate the atmosphere and reabsorb the longer wave infrared that creates heat.
Learn more about the Ice Age at The Field Museum's "Evolving Planet" exhibit and online at www.fieldmuseum.org/EVOLVINGPLANET.
Check these out
The Warren Newport Library in Gurnee suggests these titles on the Ice Age:
• "Exploring the Ice Age," by Margaret Cooper
• "The Great Ice Age," by Christopher Maynard
• "The Ice Age," by Darlene R. Stille
• "An Ice Age Hunter," by Lucilla Watson
• "The Ice Ages," by Don Nardo
• "Ice Ages of the Future," by Paul Stein