• dome
    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

    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.

  • 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

    (1561) Russian Orthodox church, now a museum, 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.

    Encyclopedic Entry: volcano
    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.

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