Across this deep preglacial valley, glacial meltwaters once drained west to the Wisconsin River, depositing sand and gravel carried south to Middleton by giant ice sheets. Today Black Earth Creek winds through this unglaciated outwash plain as Dane County's most productive trout stream. Although fish stocking and habitat improvement have helped, the creek's greatest asset is the abundant flow of cold spring water filtering through the gravel. That rapid flow turns high water fertility from farmland and sewage into fish food, keeps oxygen high and temperatures low, and scours mud and silt from the gravel bottom, all of which are necessary for trout reproduction. Evergreen plantings along the creek mark the birthplace of Madison Schools' Outdoor "Work-Learn" Conservation Program. Along the valley's edge, dolomite limestone bluffs support oak woods dating from the first days of fire protection in settlement times. Where the ground is too dry for oaks, lime-loving red cedars of notable sizes and shapes have appeared as grazing reduced the grass cover, as on the slope below. Restoring drought-resistant prairie on this dry, sunny slope could connect the park to the strip of unplowed presettlement prairie that still survives along the railroad below, a desirable goal now that prairie plants are rare and interest in replanting them is strong.