The 1868 Geological Exploration of the Fortieth Parallel, led by later U.S. Geological Survey director Clarence King, was the first to closely study the geology, soils and minerals of the Shoshone Falls area. King described the country as "strange and savage", and said of the falls themselves: "You ride upon a waste. Suddenly, you stand upon a brink. Black walls flank the abyss. A great river fights its way through the labyrinth of blackened ruins and plunges in foaming whiteness." He was also the first to speculate that the falls and canyon, rather than being formed by erosion over millennia, might have been created by "moments of great catastrophe" considering the region's chaotic volcanic history. Timothy H. O'Sullivan was also a member of the 1868 expedition, and became the first national photographer to picture the falls. O'Sullivan also returned to the area in 1874, again to photograph Shoshone Falls.