Magpie High FallsTumbling over hard, Precambrian rocks, the Magpie River will take a very, very long time to erode these cascades upstream. Magpie High Falls isn't outrageously high, with a vertical drop of about 75 feet, but it is one of the widest of the dozens of waterfalls that adjoin Lake Superior. As on all the other streams tumbling into the lake, this one is a simple geomorphology process working to smooth the gradient between the stream's headwaters and the Superior basin. A midcontinental rift 1.1 billion years back first created the depression that Lake Superior occupies, also giving birth to flood basalts and other igneous rock, like that here. Glaciers in much more recent ice ages scooped enough accumulated sediment out of the basin to shape today's version of the lake. That's the level to which the modern streams are trying to cut in their course downhill.
3 SW Wawa, ON, Canada (15 Jul 7) , looking N