Winter has once again settled over the Arb, and with this new blanket of snow comes a change in the color palette of the Arb. The browns, greens and golds of fall have been replaced by the softer hues of grey, white and blue. This change in color for the Arb also tends to bring different aspects of the Arb to the forefront of the landscape. The boulders that are scattered across the Arb for instance, now stand proudly above the dormant prairie grasses ready to tell their story.
These glacial erratics can be found in several places in the Arb, the largest of which is found just on top of the hill north of Highway 19. The others can be found near the baseball field and in the small prairie that sits next to the oak savannah in Upper Arb. These boulders have not had an easy life however, in fact they are glacial erratics that were dragged, pushed and pummeled by glaciers before finally being set down within the Arb. Roughly 50,000 years ago, the Late Wisconsin Glaciation ripped these rocks from their homes in Northern Minnesota and pushed them south as part of the Des Moines Lobe. Over the next 35,000 years, these rocks were pummeled by the ice, jostled against other rocks, and scraped across the landscape until they were ground down into their current forms. Finally, as the Des Moines receded 12,000 years ago, these glacial erratics were laid to rest in Northfield, Minnesota.
These glacial erratics are just the first chapter in the Arb’s geologic history, and many more stories are waiting to be told by the rocks of this area. So the next time you rest on one of these rocks to look up and ponder the vastness of the sky, take some time to consider the amazing stories told by the ground directly underfoot.