An underground scientist is pioneering a new way to learn what the climate was like thousands of years ago
By J. Madeleine Nash – Smithsonian magazine, January 2013,
A honeycombed cave formed untold millennia ago beneath what is now southeastern Minnesota. Larry Edwards is standing in a subterranean chamber, his headlamp illuminating a series of mineral formations. From the cathedral-like ceiling dangle tubes known as soda straws. Along a waist-high ledge squats a trio of stout stalagmites, their surfaces slick with ecru-colored ooze. “Now that’s the kind of thing we might be interested in,” Edwards says, bending to peer at one.
I hear the plink, plink, plink of falling droplets. One hits the top of a stalagmite, then spreads out, laying down a thin film of the mineral calcium carbonate, or calcite, from rainwater seeping though limestone. Drop by drop the stalagmite has grown to its present height—about 18 inches—over who knows how many centuries.
Edwards, a geochemist at the University of Minnesota and a pioneer in the use of cave formations to document ancient climate, is not planning to collect stalagmites today. But two specimens severed from their moorings when the owner of the cave complex, Spring Valley Caverns, opened a deeper passageway recently provided Edwards and his colleagues with a record of extreme rainfall events over the past 3,000 years. Edwards wonders if some of Spring Valley’s stalagmites could contain older records still, dating back to when giant glaciers covered much of the Northern Hemisphere or even to one of the distant warm periods, or interglacials, that punctuated the ice age world.
A short time later, we retrace our steps, navigating the sequence of walkways and ladders that leads to the cave’s entrance. As we step into the light, Edwards turns to me. “Do you notice all the sounds, all the smells?” he says. “When you come up, they seem so pronounced.” Edwards, renowned among paleoclimatologists for his cave findings, isn’t much of a spelunker. “It’s not that I’m claustrophobic,” he says with a shrug, “I just like it better up here.”