• volcanic cone
    Wizard Island is a small cinder cone located inside the remains of a much larger volcano, Mount Mazama. Mount Mazama was a composite cone volcano that collapsed about 7,700 years ago and formed Crater Lake, Oregon.

    Cone in a Cornfield
    In February 1943, a cinder cone formed in Paricutin, a village in central Mexico. A volcanic vent called a fumarole opened suddenly in a cornfield. Within a day, it had deposited enough material to form a cinder cone 40 meters (131 feet) high. The eruption continued for nine years, building the cone to a height of 424 meters (1,391 feet) and covering the village.

    A volcanic cone is a triangle-shaped hill formed as material from volcanic eruptions piles up around the volcanic vent, or opening in Earth’s crust
    Most volcanic cones have one volcanic crater, or central depression, at the top. They are probably the most familiar type of volcanic mountain.
    Major Types of Volcanic Cones
    Composite cones
    Composite cones are some of the most easily recognizable and imposing volcanic mountains, with sloping peaks rising several thousand meters above the landscape
    Also known as stratocones, composite cones are made up of layers of lava, volcanic ash, and fragmented rocks. These layers are built up over time as the volcano erupts through a vent or group of vents at the summit’s crater. The eruptions that form these cones, called Plinian eruptions, are violently explosive and often dangerous.
    One of the most famous stratocones in the world is Mount Fuji, Japan. The tallest mountain in Japan, Mount Fuji towers 3,776 meters (12,380 feet) above the surrounding landscape. Mount Fuji last erupted in 1707, but is still considered an active volcano.
    Mount Rainier, Washington, is another stratocone. Mount Rainier rises 4,392 meters (14,410 feet) above sea level. Over the past half million years, Mt. Rainier has produced a series of alternating lava eruptions and debris eruptions. These eruptions have given Mt. Rainier the classic layered structure and sloping shape of a composite cone. Unlike Mount Fuji, Mount Rainier’s composite cone has been carved down by a series of glaciers, giving it a craggy and rugged shape. 
    Cinder cones
    Cinder cones, sometimes called scoria cones or pyroclastic cones, are the most common types of volcanic cones. They form after violent eruptions blow lava fragments into the air, which then solidify and fall as cinders around the volcanic vent. Usually the size of gravel, these cinders are filled with many tiny bubbles trapped in the lava as it solidifies. Cinder cones stand at heights of tens of meters to hundreds of meters.  
    Cinder cones may form by themselves or when new vents open on larger, existing volcanoes. Mauna Kea, a volcano on the American island of Hawaii, and Mount Etna, a volcano on the Italian island of Sicily, are both covered with hundreds of cinder cones.   
    Other Types of Volcanic Cones
    Spatter Cones
    Volcanoes often eject small amounts of gaseous lava blobs into the air. These lava blobs, called spatter, are heavy and viscous. Viscosity refers to a substance’s resistance to flow. In this case, it refers to the spatter’s thickness. The viscosity of spatter means it often does not have time to cool before hitting the ground. 
    The lava blobs in spatter stick together as they land, piling up to form steep-sided spatter cones. Most spatter cones are very small, ranging between 1 and 5 meters (3 to 16 feet) in height, because they result from minor volcanic activity. They often form in linear groups along an eruptive fissure, or long crack, on the flank of an active volcano. A small spatter cone is called a hornito.
    Spatter cones can be found in and around the Puʻu ʻŌʻō region of Mount Kilauea in Hawaii. Continuously erupting since 1983, Kilauea’s volcanic activity is characterized by the fountaining of hot lava, making it the perfect incubator for spatter cones. 
    Tuff Cones
    Unlike spatter cones that form from lava fountaining, tuff cones form from the interaction between rising magma and bodies of water. Tuff cones are sometimes called ash cones.
    When heated rapidly by lava, water flashes to steam and expands violently, fragmenting huge amounts of lava into plumes of very fine grains of ash. This ash falls around the volcanic vent, creating an ash cone. Over time, the ash weathers into a rock known as tuff.  
    Tuff cones have steep sides and often stand between 100 and 300 meters (328 to 984 feet) high. They are much wider and have broader craters than spatter cones because they result from shallow explosions that eject materials sideways rather than upwards.   
    Diamond Head, the famous volcano near Honolulu, Hawaii, is an enormous tuff cone. The mountain is the result of a brief volcanic eruption about 200,000 years ago. During Diamond Head’s eruption period, the mountain rose from the ocean, and lava interacted with water and even a nearby coral reef. Today, Diamond Head’s rim is about a kilometer (.62 mile) from the coast, and rises about 232 meters (760 feet) above sea level.
  • Term Part of Speech Definition Encyclopedic Entry
    active volcano Noun

    volcano that has had a recorded eruption since the last glacial period, about 10,000 years ago.

    carve Verb

    to cut or slice through.

    characterize Verb

    to describe the characteristics of something.

    cinder Noun

    tiny bits of coarse lava.

    cinder cone Noun

    hill created by tiny bits of lava blown out of a volcano and fallen down around the volcanic vent. Also called a scoria cone.

    coast Noun

    edge of land along the sea or other large body of water.

    Encyclopedic Entry: coast
    composite cone Noun

    hill created by layers of volcanic lava, ash, and broken rock.

    coral reef Noun

    rocky ocean features made up of millions of coral skeletons.

    craggy Adjective

    rugged or rocky.

    crater Noun

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

    Encyclopedic Entry: crater
    crust Noun

    rocky outermost layer of Earth or other planet.

    Encyclopedic Entry: crust
    debris Noun

    remains of something broken or destroyed; waste, or garbage.

    depression Noun

    indentation or dip in the landscape.

    eject Verb

    to get rid of or throw out.

    enormous Adjective

    very large.

    erupt Verb

    to explode or suddenly eject material.

    expand Verb

    to grow or get larger.

    fine Adjective

    very thin.

    fissure Noun

    narrow opening or crack.

    flank Noun

    side of something.

    fragment Noun

    piece or part.

    glacier Noun

    mass of ice that moves slowly over land.

    Encyclopedic Entry: glacier
    gravel Noun

    small stones or pebbles.

    hill Noun

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

    Encyclopedic Entry: hill
    hornito Noun

    small spatter cone, or mound of material ejected by a volcano.

    imposing Adjective

    large or very impressive.

    incubator Noun

    location that supports the development of something.

    landscape Noun

    the geographic features of a region.

    Encyclopedic Entry: landscape
    lava Noun

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

    magma Noun

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

    Encyclopedic Entry: magma
    mountain Noun

    landmass that forms as tectonic plates interact with each other.

    Plinian eruption Noun

    powerful, violent volcanic explosion characterized by pyroclastic flows and ejection of material high into the atmosphere.

    pyroclastic cone Noun

    hill created by tiny bits of lava blown out of a volcano and fallen down around the volcanic vent. Also called a cinder cone.

    recognizable Adjective

    able to be identified.

    rock Noun

    natural substance composed of solid mineral matter.

    rugged Adjective

    having an irregular or jagged surface.

    scoria cone Noun

    hill created by tiny bits of lava blown out of a volcano and fallen down around the volcanic vent. Also called a cinder cone.

    sea level Noun

    base level for measuring elevations. Sea level is determined by measurements taken over a 19-year cycle.

    Encyclopedic Entry: sea level
    solidify Verb

    to make solid.

    spatter cone Noun

    hill formed by partially liquid lava dripping and falling from a volcanic eruption.

    steam Noun

    water vapor.

    Strombolian eruption Noun

    mildly violent explosion of a volcano.

    tuff Noun

    type of rock formed from hardened volcanic ash.

    tuff cone Noun

    hill formed by ash falling from a volcanic eruption. Also known as an ash cone.

    viscosity Noun

    measure of the resistance of a fluid to a force or disturbance.

    volcanic ash Noun

    fragments of lava less than 2 millimeters across.

    Encyclopedic Entry: volcanic ash
    volcanic cone Noun

    hill created by a volcanic eruption.

    Encyclopedic Entry: volcanic cone
    volcanic eruption Noun

    activity that includes a discharge of gas, ash, or lava from a volcano.

    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
    weather Verb

    to change as a result of exposure to wind, rain, or other atmospheric conditions.