Ann Arbor on Ice
About 14,000 years ago, as the climate began to warm, the Huron-Erie Lobe stalled over Ann Arbor, its forward movement pretty much equal to its melt. The western edge of the glacier, or ice margin, lay atop the west side of the city. Although the glacier was relatively stationary, the internal movement of the ice proceeded to dump massive quantities of glacial till--unsorted sediment including sand, gravel, silt, and clay--in a ridge known as an end moraine. This process of deposition built the sudden rise along Ann Arbor's west side. If you've ever labored to bike up the incline on westbound Liberty between 7th and Stadium, or if you've ever sweated the walk up Spring Street to the northwest tip of Hunt Park, you've climbed this moraine, and have an idle glacier to thank for your rock-hard calves. It is formally known as the Fort Wayne Moraine, because it extends all the way to Fort Wayne, Indiana.
Glacial deposition also takes the form of erratics, or large, isolated rocks and boulders dropped by the ice. One notable erratic is the aforementioned painted rock. It did not come to rest at its current location, the corner of Hill and Washtenaw, via glacier, however; it was placed there in 1932 under the direction of city parks superintendent Eli Gallup, who, drawn to the limestone rock's size and glacial striations, rescued it from a landfill with the hope of sharing it with the public. There are a few other Gallup erratics prominently displayed around town, including one on Huron near First, in honor of town founder John Allen's settlement. You'll also find one, spangled with rosy flecks of quartz, in the Bird Hills Nature Area, where steep, scenic trails crisscross the Fort Wayne Moraine.