Pleistocene continental glaciers: a single ice age following a Genesis Flood or multiple ice ages?

Young-earth creationist Larry Vardiman (1993, 2009) has proposed that the continental glaciation that occurred during the Pleistocene Epoch in North America, Greenland, northern Europe, and northern Asia (Figure 1) was a single ice-age event that occurred following the Genesis worldwide Flood, about 4500 years ago or about 2500 bce, and postulates that the earth is about 6000 years old based on Bishop Ussher’s estimate (Ussher 1786). Another creationist estimate (Osgood 1981) suggests that the Flood occurred in 2304 bce, but Vardiman’s choice of 2500 bce is more common and will be used here.