A gorge is an erosional valley carved by the action of a river. A valley is called a gorge if it is very steep and narrow, with escarpments or cliffs on both sides. Often the term canyon is used synonymously, the two words are pretty well interchangeable. The difference between both terms is, that canyon is borrowed from Spanish cañón, and gorge from French. For example in the USA, most canyons are in the south-west, while the Atlantic states have gorges.
Gorges are sometimes called Slot Canyon, which is rather descriptive. It means a slot-like morphology, the depth exceeds the with by factor 10 or more.
Many gorges and canyons are connected to limestone and karstification. Often the process of cave development and collapse produces gorges. But the biggest canyons are formed simply by a combination of uplift and erosion or in connection with glaciation. Rivers draining an area always flow downhill in the shortest possible way. The steeper their bed is, the more energy and thus erosion is produced. As a result rivers cut into the surrounding rock, the steeper the faster. When the valley reaches a certain depth the water flows with much less energy to the sea, the valley stays where it is. As a result, valleys tend to wander from the sea to the source.
The most narrow gorges, sometimes they are hundred meters deep but only two or three meters wide, are very similar to caves. They are like roofless caves. And there are even gorges which are actually roofless caves. So we decided to list gorges on showcaves.com although they are actually not underground.
Especially in Europe, in the Alps, there are numerous narrow gorges, which were developed with paths and bridges. The trails are often built of wood, because they are regularly destroyed by floods. But if you ever visited such a gorge you know its woth the effort, and you can see the similarity between a cave and a gorge.