Encyclopedic Entry

Although "duomo" often refers to any cathedral in Italy, "The Duomo" almost always refers to the cathedral in Florence, above.

Photograph by Patrick McCarthy, MyShot

Buckyballs
The geodesic dome was patented by American mathematician, inventor, and architect Buckminster Fuller. Years later, an unusual, 60-atom formation of the element carbon was discovered. It resembled the shape of a geodesic dome. The discoverers of this molecule named their discovery the buckminsterfullerene, nicknamed the buckyball.

A dome is a curved formation or structure. It is shaped like half of a sphere. Imagine cutting an orange in half, and placing it cut-side-down on a table. This is the shape of a dome, although most domes in nature are not perfectly rounded.

Some natural domes develop when magma from deep within the Earth pushes up surface rock layers. This type of geologic dome can form as magma intrudes between two layers of sedimentary rock. The magma creates a dome or triangle shape as it pushes the other layers apart. The hardened magma that forms this type of dome is called laccolith.

Lava domes form as lava hardens atop volcanic vents. In the Chaitn Volcano in Chile, an ongoing eruption that began in 2008 is forming a lava dome next to another one that completely filled the crater when the volcano erupted 9,400 years ago.

Another kind of dome is shaped primarily by weathering and erosion, which cause curved sheets of rock to separate from a large rock mass. The Cima Dome in the Mojave Desert, in the U.S. state of California, was once a mountain. Over time, weathering and erosion wore away the mountain and smoothed it into a rounded dome.

Salt Domes

Salt domes result when rock salt rises through overlying sedimentary rock. Salt accumulates as ancient seas dry up over time. Eventually, sediments form over this layer of salt. Salt is less dense than most other rocks, and it slowly moves upward toward the surface, forming a dome-shaped hill.

One of the most famous salt domes is Avery Island, in the U.S. state of Louisiana. Avery Island is a salt dome surrounded by low-lying swamps of the Mississippi River delta.

Eventually, these salt domes can break through the surface rock layers. Sometimes, the salt beneath a salt dome is enough to create a salt glacier. Salt glaciers behave like ice glaciers, moving slowly down a mountainside. Salt glaciers are most active in the winter, when they are filled with moisture from snow and rain. The Zagros Mountains in Iraq and Iran have formed over a series of salt domes, and have active salt glaciers.


Salt domes are important sites for industry. Salt is a valuable mineral used in the production of plastics, pesticides, preservatives, and fire extinguishing equipment. The salt mines near Avery Island and in the Zagros Mountains are hundreds of years old.

Salt domes are also important for the petroleum industry. Salt domes trap oil between layers of rock. Oil wells can drill into the salt dome and extract oil. Salt domes on the coast and beneath the Gulf of Mexico often reveal oil deposits.

Architectural Domes

Domes are one of the most familiar features in architecture, or the structure of buildings. One of the most famous domes is the Taj Mahal, a mausoleum in Agra, India.

Domes are frequently used for government buildings, such as the U.S. Capitol in Washington, D.C. They are also used in religious architecture, such as the Dome of the Rock, an Islamic shrine in Jerusalem, Israel; and the Florence Cathedral, a Catholic church in Florence, Italy. (The Florence Cathedral is even nicknamed the Duomo or Brunelleschis Dome, after its architect, Filippo Brunelleschi.)

Russian architecture features domes shaped like onions. The most famous of these onion domes are probably those of St. Basil's Cathedral in Moscow.

Geodesic domes are created using a complex series of triangles. Geodesic domes are an efficient architectural design; they are stronger, lighter, and quicker to construct than more traditional buildings. They also enclose a large amount of space with minimal materials, labor, and energy.

Although geodesic domes enclose a lot of space, the shape and space are not easily used by people. Most furniture and machinery is made for flat walls. Although some geodesic houses have been built, most geodesic domes are used for public aviaries or sports facilities.

Vocabulary

Term Part of Speech Definition Encyclopedic Entry

accumulate

Verb

to gather or collect.

ancient

Adjective

very old.

architect

Noun

person who designs buildings or other large structures.

architecture

Noun

style and design of buildings or open spaces.

aviary

Noun

enclosed area where birds are kept.

cathedral

Noun

important regional church.

Catholic

Adjective

having to do with the Christian denomination with the Pope as its leader.

church

Noun

building used for spiritual worship and religious practices.

construct

Verb

to build or erect.

crater

Noun

bowl-shaped depression formed by a volcanic eruption or impact of a meteorite.

Encyclopedic Entry: crater

delta

Noun

the flat, low-lying plain that sometimes forms at the mouth of a river from deposits of sediments.

Encyclopedic Entry: delta

dense

Adjective

having parts or molecules that are packed closely together.

dome

Noun

shape that is half of a sphere.

Encyclopedic Entry: dome

Dome of the Rock

Noun

Islamic shrine in Jerusalem, Israel.

Earth

Noun

our planet, the third from the Sun. The Earth is the only place in the known universe that supports life.

Encyclopedic Entry: Earth

efficient

Adjective

performing a task with skill and minimal waste.

energy

Noun

capacity to do work.

erosion

Noun

act in which earth is worn away, often by water, wind, or ice.

Encyclopedic Entry: erosion

eruption

Noun

release of material from an opening in the Earth's crust.

extinguish

Verb

to put out a fire or flame.

extract

Verb

to pull out.

Filippo Brunelleschi

Noun

(1377-1446) Italian architect and engineer.

geodesic dome

Noun

architectural structure shaped like a sphere and made of a complex shell of curved triangle shapes.

geologic

Adjective

having to do with the physical formations of the Earth.

glacier

Noun

mass of ice that moves slowly over land.

Encyclopedic Entry: glacier

government

Noun

system or order of a nation, state, or other political unit.

hill

Noun

land that rises above its surroundings and has a rounded summit, usually less than 300 meters (1,000 feet).

Encyclopedic Entry: hill

industry

Noun

activity that produces goods and services.

labor

Noun

work or employment.

laccolith

Noun

magma that is trapped between layers of sedimentary rock, forming a domed hill. Also called laccolite.

lava

Noun

molten rock, or magma, that erupts from volcanoes or fissures in the Earth's surface.

lava dome

Noun

feature formed as lava hardens over a volcanic vent.

magma

Noun

molten, or partially melted, rock beneath the Earth's surface.

Encyclopedic Entry: magma

mausoleum

Noun

impressive tomb or burial site.

mineral

Noun

inorganic material that has a characteristic chemical composition and specific crystal structure.

moisture

Noun

wetness.

oil

Noun

fossil fuel formed from the remains of marine plants and animals. Also known as petroleum or crude oil.

oil deposit

Noun

natural accumulation of petroleum, usually underground or under the ocean floor.

onion dome

Noun

shape of a half-sphere with a thin, pointed top.

pesticide

Noun

natural or manufactured substance used to kill organisms that threaten agriculture or are undesirable. Pesticides can be fungicides (which kill harmful fungi), insecticides (which kill harmful insects), herbicides (which kill harmful plants), or rodenticides (which kill harmful rodents.)

petroleum

Noun

fossil fuel formed from the remains of ancient organisms. Also called crude oil.

plastic

Noun

chemical material that can be easily shaped when heated to a high temperature.

preservative

Noun

substance that prevents food or other organic material from rotting or decomposing.

primarily

Adverb

first or most important.

rain

Noun

liquid precipitation.

Encyclopedic Entry: rain

rock

Noun

natural substance composed of solid mineral matter.

rock salt

Noun

natural mineral form of salt (sodium chloride.) Also called halite.

salt

Noun

mineral often used as a preservative or flavoring.

salt dome

Noun

structure formed as water evaporates from a salty lake or sea. The remaining salt is buried by sediments, but eventually pierces through the rock, forming a hill.

salt glacier

Noun

large block of salt from a salt dome that has pierced the surface layer of rock and earth, and is slowly moving down the mountain or hill.

salt mine

Noun

industrial site where salt is extracted from deposits within the Earth.

sediment

Noun

solid material transported and deposited by water, ice, and wind.

Encyclopedic Entry: sediment

sedimentary rock

Noun

rock formed from fragments of other rocks or the remains of plants or animals.

shrine

Noun

place of worship or spiritual devotion.

snow

Noun

precipitation made of ice crystals.

sphere

Noun

round object.

St. Basil's Cathedral

Noun

(1555) Russian Orthodox cathedral in Moscow, Russia.

swamp

Noun

land permanently saturated with water and sometimes covered with it.

Encyclopedic Entry: swamp

Taj Mahal

Noun

(1632) large, white mausoleum complex in Agra, India, built by Shah Jahan for his wife Mumtaz.

volcanic

Adjective

having to do with volcanoes.

volcanic vent

Noun

opening in the Earth's crust where lava and gases escape to the Earth's surface or atmosphere.

volcano

Noun

an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions.

weathering

Noun

the breaking down or dissolving of the Earth's surface rocks and minerals.

Encyclopedic Entry: weathering

well

Noun

a hole drilled in the Earth to obtain a liquid or gaseous substance.

Credits

Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Writer

Kim Rutledge
Melissa McDaniel
Diane Boudreau
Tara Ramroop
Santani Teng
Erin Sprout
Hilary Costa
Hilary Hall
Jeff Hunt

Illustrator

Tim Gunther
Mary Crooks, National Geographic Society

Editor

Kara West
Jeannie Evers

Educator Reviewer

Nancy Wynne

Producer

Caryl-Sue, National Geographic Society

Sources

Dunn, Margery G. (Editor). (1989, 1993). "Exploring Your World: The Adventure of Geography." Washington, D.C.: National Geographic Society.

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