Taum Sauk Hydroelectric Power Station is a pure pumped-storage hydroelectric plant, designed to help meet peak power demands during the day. Located more than 80 kilometers from the nearest water source, the Mississippi river, there is no natural primary flow available for generation, unlike most other pumped storage sites
In 2005, the plant had to shut down when the upper reservoir suffered a catastrophic failure releasing 4 million cubic-meters of water in twelve minutes.
The plant returned to service after a gap of four years. The rebuilt upper reservoir is now considered an engineering milestone, being the largest roller-compacted concrete dam in North America.

From here, via here and there


More pictures from Hughes Mountain. Columnar rhyolite (really a devitrified rhyolitic ash flow tuff) covered in lichen, with fiamme and flow banding.

Hughes Mountain is an igneous knob in the St Francois Mountains of southeastern Missouri, the product of intercontinental volcanism during the late Precambrian, roughly 1.5 billion years ago. Other notable spots within the St Francois Mountains are Elephant Rocks, Johnsons Shutins, and Taum Sauk Mountain.