Crossing the Snake

February 12, 2013

Crossing the snake

Photographer: Stu Witmer
Summary Author: Stu Witmer

February 2013 Viewer's Choice The Snake River contains many superlatives. For example, Shoshone Falls is higher than Niagara and Hell’s Canyon is deeper than the Grand Canyon. The Snake rises in Yellowstone National Park and is the largest tributary of the Columbia River. In its course of over 1,000 miles, the river drops more than 9,000 ft (2,740 m) and discharges about 8.3 cu mi (34.5 cu km) of water into the Columbia every year. The photo above was taken looking west just after sunrise from a point downstream of Twin Falls, Idaho. From here, none of the river's drama is evident and it looks like just another pretty river.

But, consider the horizon for a moment. Flat isn’t it? This flatness is the result of millions of years worth of eruptions from volcanic calderas, some up to 40 mi (64 km) wide, dumping enormous amounts of rhyolitic magma and ash upon the landscape. Layer upon layer of basaltic lava flowing from thousands of shield volcanoes then covered these basement rocks to depths up to 6,000 ft (1,830 m). All of this happened because the North American tectonic plate is moving slowly over the hotspot that's now beneath Yellowstone National Park. More recently, about 15,000 years ago, the Pleistocene Lake Bonneville (forerunner of the Great Salt Lake) suddenly let loose colossal amounts of water onto all this rock. This was similar to events further north where glacial Lake Missoula repeatedly collapsed creating on a surge of water that ripped away much of the lava plateau and left behind the Channeled Scablands we see today in parts of Washington. Note too that perspective makes the clouds and river seem to lead toward a single vanishing point right in the middle of the image. Photo taken October 5, 2012.

Photo Details: Camera: Canon PowerShot SD1300 IS; Focal Length: 5.0mm; Aperture: f/2.8; Exposure Time: 0.0080 s (1/125); ISO equiv: 80; Software: GIMP 2.