How does a cavern lead to the formation of a gorge

The most common is erosion due to streams or rivers. Streams carve through hard layers of rock , breaking down or eroding it.

Sediment from the worn-away rock is then carried downstream. Over time, this erosion will form the steep walls of a gorge. The flooding of streams or rivers increases the speed and intensity of this erosion, creating deeper and wider gorges.

Geologic uplift also forms gorges. Geologic uplift is the upward movement of the Earths surface. Geologic uplift is often associated with earthquakes and orogeny , the process of creating mountains.

During geologic uplift, rock layers beneath the Earths surface bump against the surface layers. Softer layers of surface rock erode. Erosion and geologic uplift often work together to create gorges. Parts of streams or rivers can be elevated, along with land, during the process of geologic uplift. As rivers or streams flow across this uplifted surface, waterfalls form.

Over time, the power of the waterfall erodes the softer rock layers underneath, causing the original river bed to collapse and create a gorge. Macocha Gorge in the Jihomoravsk region of the Czech Republic was probably formed by the collapse of an underground cave that had been eroded by the Punkva River.

The movement and melting of glaciers can also produce gorges. Glaciers cut deep valleys into the Earths surface. These rivers of ice can create huge canyons and sharp, steep gorges. As glaciers melt, or retreat, these gorges and canyons are exposed. The Columbia River Gorge, located in the U.

Engineers have purposely flooded gorges in order to create waterways and dams. These dams generate hydroelectricity , or electricity powered by water. Upstream from the dam, the Qutang, Wu, and Xilang gorges were partially submerged in order to create a waterway. The new waterway would allow freight ships to navigate from the East China Sea, part of the Pacific Ocean, to the city of Chongqing, about 2, kilometers 1, miles inland.

The 26 turbines of the Three Gorges Dam generate approximately 18, megawatts of electricity for Shanghai and other cities.

However, many people worry about the environmental impacts of the dam and criticize the fact that more than a million Chinese families were forced to move from their homes near the gorges in order to complete the construction. Many geological discoveries have been made at gorges because gorges often expose layers of rock that go back thousands of years.

Olduvai Gorge in Tanzania has layers dating as far back as 2 million years. The Olduvai Gorge is famous for the fossils and ancient tools found there by scientists Louis, Mary, and Richard Leakey. These remains of ancient animals and plants provide clues about early humans. Meriwether Lewis, William Clark and their Corps of Discovery were not only challenged by the landforms of the gorge, but also by the extreme weather that often halted their journey.

One could say that the success of the Lewis and Clark Expedition was based upon the "rock and roll" of the Columbia River Gorge!

Initially the cave descends steeply, often down dip or along joints, via a series of small cascades or pitches. On reaching the water table the passage enters the phreatic, sub water table zone, marked by a water-filled section known as a sump. These phreatic passages display a characteristic looping profile as the water flows down a bedding plane, and then ascends up a joint or other fracture to gain higher bedding planes within the limestone en route to the resurgence.

As time progresses, the cave will tend towards a more graded even profile. Erosion at the spring outlet may cause the stream to find a new lower course, leaving the former passage high and dry. In this way a whole series of abandoned former stream courses may lie above the active streamway. Detailed studies of these passages can give clues about how the cave evolved over time and former water-table positions.

These abandoned passages may become modified by breakdown and collapse, be partially infilled by sediment or stalagmite deposition, or even become reactivated or destroyed at a later date. The style of cave passage depends on the frequency of bedding planes, fissures and fractures within the rock. The material eroded during these periods was deposited as large alluvial fans marked as 'head' on most geological maps extending out from the gorge mouth, an excellent example occurs at Burrington Combe.

On western Mendip, many modern valleys follow earlier filled-in Triassic valleys where erosion has picked out the softer Mercia Mudstone, in preference to the harder, more resistant Carboniferous Limestone.

Apart from a few exceptions in the extreme east, all the valleys cut into the limestone are now dry. This is due to the development of underground drainage and the formation of extensive cave systems. Home Overview maps Acknowledgements Site map Copyright. This site is hosted by the British Geological Survey but responsibility for the content of the site lies with Foundations of the Mendips website not with the British Geological Survey.