How Gorges Are Formed

Gorges and Canyons

A gorge and a canyon are basically the same thing: a valley marked by steep cliffs with a watercourse running along its bottom. The simple answer to how a gorge is formed is by water erosion, but in actual practice, a number of factors come together to make a gorge possible.

Flooding

One potential source of gorge formation is major, systematic flooding. Geologists believe that during the last ice age, rapid melting of the great glaciers caused catastrophic flooding that carved out several gorges and canyons along already existing waterways. The same pattern can be seen today, albeit in a much less violent form. Spring thawing regularly causes river flooding in areas where rivers are fed primarily by glaciers. The gorges formed when the erosive power of the flooding was slowed down upon harder strata of rock, causing cliffs to form and the flooding to dig down, rather than out.

Waterfalls

Another source of gorge formation is a waterfall. Waterfalls themselves are usually the product of geologic uplift. When there is geologic uplift in an area that is already home to a watercourse, the resulting change in elevation creates a waterfall. That waterfall creates accelerated water flow and erosion, which over time will cut back on itself, creating a gorge. Even if the watercourse lacks the power to carve the hard rock in its own bed away, if softer rock has been exposed below by geologic uplift, that will be eroded and washed away. This undermines the original river bed, causing eventual and successive collapse, forming a gorge.

References

• Canyoneers: Gorge Formation
• Gorge Formation in Crete
• Gorges Formed by Rapid Flooding

Resources

• Animation: How a Waterfall Can Create a Gorge