The Lake - Piecing Together the Past
Beach ridges left from earlier times show where the lakeshore was located in the past. Topographic maps give the elevations of the ancient beaches. We use global positioning system (GPS) equipment to find our location on the map. The beach elevation tells us the water level of the ancient lake. Organic materials in the deposits have been radiocarbon dated to find out when the beach ridges formed.
Some past shorelines are missing. Some have eroded away. Others are underwater. Scientists have found river channels and traces of forests far offshore on the lake bottom—evidence of when the lake level was much lower than it is today.
Several species of sand wasps make the beach-ridge plain their home. They dig burrows in the sand to make their nests. Sand wasps are solitary, but hundreds of wasps can build nests close to one another, creating what looks like a huge colony.
The thirteen-lined ground squirrel has more stripes than a chipmunk. The stripes are closely spaced and sometimes have spots.