Horseshoe Bend geology

The dramatic vista of Horseshoe Bend in the Colorado River is a great example of an incised meander whose formation began millions of years ago. While the landscape may appear pretty permanent now, it didn’t always look this way. Indeed, the Earth is constantly changing and will continue to do so until the end of time.

While the Colorado River is now trapped at the bottom of a steep-sided canyon, it once flowed across a flatter surface but at a much lower elevation. The Colorado Plateau today is a raised region of America located on the western side of the Rocky Mountains.

It formed as a result of tectonic movement that forced the land of southern Utah and northern Arizona up higher than the surrounding terrain. In the Late Cretaceous era the plateau was at sea level; today parts of its surface stand around 2,000 metres (6,500 feet) above sea level.

 
Before this plateau formed, the Colorado River flowed across the land like any other. The middle course – which is where you find meanders like Horseshoe Bend – is where the stream has the most energy and water. The fast-flowing water carries stones, sand and corrosive substances, which together create an erosive force to be reckoned with.

Like all meanders, the bends in the Colorado formed due to a cycle of erosion and deposition. First, the outside of the bend – where the water flows fastest – is worn away. This eroded rock and sediment is then deposited by the slower- flowing water inside of the bend. The continuous erosion and deposition causes the river to meander and migrate downstream.

 
Dramatic landforms like Horseshoe Bend emerged after the gradual uplift of the Colorado Plateau caused the river to carve its path down through the ancient sandstone, instead of eroding from side to side. This is because water will always follow the steepest route. Over millennia, the banks of the river grew ever steeper, until eventually the river became entrenched at the base of a canyon.