During the last ice age, glacial lobes crept south from the Arctic and leveled much of Minnesota, Wisconsin, Illinois, and Iowa. However, they spared an area of about 15,000 square miles, which includes parts of each of those states. This is the Driftless Region. It is characterized by rolling hills and river valleys and sports some very special geological features. About 19,000 years ago, when the ice age temperatures hit their lowest, spring and summer water seeped into small cracks in the limestone or dolomite bedrock, causing it to crack when the water froze and expanded upon winter's return. When the glaciers receded thousands of years later, great flows of glacial meltwater exacerbated these fissures simply by running through them. Limestone is easily erodable by the very slight acid in water. This process created various caverns and crevices and sinkholes that are widespread in the Driftless Region. It is upon this karst topography, as it is called, that algific slopes depend.
In the winter, cold air seeps into the limestone or dolomite bedrock of a slope via sinkholes in the upland ground surface. The air supercools the rocks and continues to flow downward until, met by an impenetrable layer of shale or slate, it is forced to move horizontally and exit the system by way of vents in the side of the slope. This cool air released onto what is most often a north-facing slope creates an unusually cold microclimate. In the spring, when snowmelt begins to seep into the ground through those same sinkholes, it is frozen by the rocks which are still much colder that the outer environment. This spring-forming sub-surface ice persists throughout the summer, sustaining the supply of cold air being released onto the slope.
The slope is covered by broken rock rubble called talus over which a thin soil is likely to support fewer trees than the surrounding area. What this ecosystem does support is a rare community of species suited for the cold temperatures. Some are normally found in boreal forest or tundra; others are glacial species that have survived in these scattered and isolated habitats for the past 12,000 years without changing very much. One of these is a snail formerly thought to have died out when the last glacier retreated. Geologists found fossil records of it but were beyond surprised to be told by a snail specialist in 1953 that it is still with us to this day.
These are acre lessons in ferns and mosses, their chilly respiration a paradox on skin in Iowan Augusts. In a quick stroll from the soft-serve joint or on a walk with the dog, Decorah residents are confronted by the positively ancient nature of the land they live on. I first visited this particular slope with a high school biology class. There is no doubt that an ecologist of any sort can find great interest in this ecosystem. Researchers from all over the country have been drawn to our area to have a look. Yet I wonder if there is actually something more to an acquaintance with an algific slope than first meets the eye--or the researching probe.
In my conversations with people concerned about the questions of perception and worldview as they affect environmental degradation, I often come upon this question of time and our society's understanding of it. Some have said that our concept of time is too narrow, that it must expand to encompass the whole of our ancestry, the children of our children's children, and beyond. Many cite the Native American concept of always taking into consideration the well-being of the next seven generations when making a decision.
The algific slope, though not necessarily any older than the land around it, supports a community that is a unique and visible testament to the relative youth of our species--not to mention modern North American society. If it is true that regaining a sense of deep-time is essential in the transformation of our culture, what better place to start than the recognition of such local land histories as the amazing stories that they are? Here could begin a convergence of the environmental sciences with reverence of this aged earth. What a powerful duo they could make in the effort to support life on this planet. So we keep on. For now, we teach our children about the cold, cold air and the great grandfather rocks and the little snails that have been here for thousands of years, since before all of us were born, since before time as we know it.
Hannah McCargar wrote this piece before coming to Lost Valley to be an intern earlier this year. She can be reached at [email protected].
(c)2005 Talking Leaves
Summer/Fall 2005
Volume 15, Numbers 2 & 3
Deep Ecology, Permaculture, & Peace