Canyon | National Geographic Society (2023)

A canyon is a deep, narrow valley with steep sides. “

Canyon

” comes from the Spanish word cañon, which means “tube” or “pipe.” The term “gorge” is often used to mean “

canyon

,” but a

gorge

is almost always

steeper

and narrower than a

canyon

.

The movement of rivers, the processes of weathering and erosion, and tectonic activity create

canyons

.

River Canyons

The most familiar type of

canyon

is probably the

river

canyon

. The water pressure of a

river

can cut deep into a river bed. Sediments from the

river

bed

are carried downstream, creating a deep, narrow channel.

Rivers

that lie at the bottom of deep

canyons

are known as entrenched rivers. They are entrenched because, unlike

rivers

in wide, flat flood plains, they do not meander and change their course.

The Yarlung Zangbo Grand Canyon in Tibet, a region of southwestern China, was formed over millions of years by the Yarlung Zangbo

River

. This

canyon

is the deepest in the world—at some points extending more than 5,300 meters (17,490 feet) from top to bottom. Yarlung Zangbo

Canyon

is also one of the world’s longest

canyons

, at about 500 kilometers (310 miles).

Weathering and Erosion

Weathering

and

erosion

also contribute to the formation of

canyons

. In winter, water seeps into cracks in the rock. This water freezes. As water freezes, it expands and turns into ice.

Ice

forces the cracks to become larger and larger, eroding bits of stone in the process. During brief, heavy rains, water rushes down the cracks, eroding even more rocks and stone. As more rocks crumble and fall, the

canyon

grows wider at the top than at the bottom.

When this process happens in soft rock, such as sandstone, it can lead to the development of slot canyons.

Slot

canyons

are very narrow and deep. Sometimes, a

slot

canyon

can be less than a meter (3 feet) wide, but hundreds of meters deep.

Slot

canyons

can be dangerous. Their sides are usually very smooth and difficult to climb.

Some

canyons

with hard, underlying rock may develop cliffs and ledges after their softer, surface rock erodes. These ledges look like giant steps.

Sometimes, entire civilizations can develop on and around these

canyon

ledges. Native American nations, such as the Hopi and Sinagua, made

cliff

dwellings.

Cliff

dwellings

were apartment-style shelters that housed hundreds of people. The shaded, elevated ledges in Walnut

Canyon

and

Canyon

de Chelly, in Arizona, provided protection from hostile neighbors and the burning desert sun.

Hard-rock

canyons

that are open at one end are called box canyons. The

Hopi

and Navajo people often used

box

canyons

as natural corrals for sheep and cattle. They simply built a gate on the open side of the

box

canyon

, and closed it when the animals were inside.

Limestone is a type of hard rock often found in

canyons

. Sometimes,

limestone

erodes and forms caves beneath the earth. As the ceilings of these

caves

collapse,

canyons

form. The Yorkshire Dales, an area in northern England, is a collection of

river

valleys

and

canyons

created by

limestone

cave

collapses.

Tectonic Uplift

Canyons

are also formed by

tectonic activity

. As tectonic plates beneath the Earth’s crust shift and collide, their movement can change the area’s landscape. Sometimes,

tectonic activity

causes an area of the Earth’s

crust

to rise higher than the surrounding land. This process is called

tectonic uplift

.

Tectonic uplift

can create plateaus and mountains.

Rivers

and glaciers that cut through these

elevated

areas of land create deep

canyons

.

The

Grand

Canyon

, in the U.S. state of Arizona, is a product of

tectonic uplift

. The

Grand

Canyon

, up to 447 kilometers (277 miles) long, 29 kilometers (18 miles) wide, and 1.8 kilometers (6,000 feet) deep, is the largest

canyon

in the United States. The

Grand

Canyon

has been carved, over millions of years, as the Colorado

River

cuts through the Colorado

Plateau

. The Colorado

Plateau

is a large area that was

elevated

through

tectonic uplift

millions of years ago. Geologists debate the age of the

canyon

itself—it may be between 5 million and 70 million years old.

Canyons Reveal Earth’s History

Canyons

are like silent journals of an area’s history over thousands or even millions of years. By studying the exposed layers of rock in a

canyon

wall, experts can learn about how the climate changed, what kind of organisms were alive at certain times, and perhaps even how the

canyon

may change in the future.

For example,

geologists

studying layers of rock in the Columbia

River

Gorge

, in the U.S. states of Washington and Oregon, discovered that the oldest rocks there are at least 17 million years old. They also found out the rocks are dark-black basalt, made from hardened lava. From this,

geologists

determined that the rocks formed when volcanoes erupted and their

lava

spilled out onto the land. Over millions of years, the Columbia

River

and Ice Age

glaciers

cut through the area and exposed its volcanic beginnings.

Canyons

are also important to paleontology, or the study of fossils.

Fossils

are often best preserved in dry, hot areas. Since

canyons

usually form under the same conditions, they are good places to examine

fossils

.

The layers of

sediment

revealed by a

canyon

can make it easier to date

fossils

. For example, a new area of dinosaur tracks was discovered in the U.S. state of Utah at Glen

Canyon

National Recreation Area in 2009. These tracks reveal new information about a group of

dinosaurs

called ornithopods. Paleontologists analyzed the layers of rock surrounding the

fossils

to estimate how old they were. These new

dinosaur

tracks show that ornithopods were alive 20 million years earlier than scientists thought.

Geologists

study

canyons

to

determine

how the

landscape

will change in the future. The

erosion

patterns and thickness of different layers can reveal the

climate

during different years. A series of very dry years will have very thin layers of rock, when little

erosion

took place. The overall pattern of

erosion

and layering reveals the rate of water flow, from both the

river

and rain, through a

canyon

.

Geologists

estimate

that the

Grand

Canyon

, for example, is being eroded at a rate of 0.3 meters (1 foot) every 200 years. The Colorado

Plateau

, the geologic area where the

Grand

Canyon

is located, is a very stable area.

Geologists

expect the

Grand

Canyon

to continue to deepen as long as the Colorado

River

flows.

Submarine Canyons

Some of the deepest

canyons

lie beneath the ocean. These submarine

canyons

cut into continental shelves and continental slopes—the edges of

continents

that are underwater.

Some

submarine

canyons

were carved by

rivers

that flowed during periods when the sea level was lower, and the

continental

shelves were exposed. The Hudson

Canyon

extends 750 kilometers (450 miles) into the Atlantic Ocean, from the mouth of the Hudson

River

, in the U.S. states of New York and New Jersey. At least part of the Hudson

Canyon

was the

river

bed

during the last

ice

age

, when

sea levels

were much lower.

Submarine

canyons

can also develop when powerful ocean currents sweep away

sediments

. Just as

rivers

erode land, these

currents

carve deep

canyons

in the ocean floor. Strong

currents

of the Atlantic Ocean prevent Whittard

Canyon

, about 400 kilometers (248 miles) south of the coast of Ireland, from filling with

sediment

. Scientists studying Whittard

Canyon

believe glacial water mixed with seawater to rush into the

submarine

canyon

thousands of years ago.

The formation of some

submarine

canyons

is still a mystery. Monterey

Canyon

is a deep

submarine

canyon

off the coast of the U.S. state of California. It has been compared to the

Grand

Canyon

because of its size. It is 152 kilometers (95 miles) long and 3.2 kilometers (2 miles) deep at its deepest point.

Geologists

still aren’t certain how Monterey

Canyon

was formed. One theory is that the

canyon

was formed by an ancient outlet of the Sacramento or Colorado

Rivers

. Another theory is that it was formed by

tectonic activity

—an earthquake splitting apart the rock with enormous force. Scientists believe the

canyon

was formed 25 million to 30 million years ago.

The depth of

submarine

canyons

makes them hard to explore. Scientists usually use remotely operated vehicles (

ROVs

) to conduct studies. Sometimes, they can use a submersible, a special kind of

submarine

. The Monterey Bay Aquarium Research Institute (MBARI) uses a vehicle called Ventana to explore Monterey Canyon. Through the Ventana and other research vehicles, MBARI scientists have discovered new species of organisms living in the

canyon

, from tiny sea anemones to giant squid.

National Geographic Magazine: Glen Canyon RevealedNational Geographic Magazine: The Grandest CanyonNational Park Service: Grand Canyon National Park—Geologic FormationsSubmarine Integrated Monitoring Network: Submarine Canyons