Volcanic plug

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  Caldera

  A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption such as the ones at Yellowstone National Park in the US and Glen Coe in Scotland. They are sometimes confused with volcanic craters. The word comes from Spanish caldera, and this from...
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  Volcano

  A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, ash and gases to escape from below the surface. The word volcano is derived from the name of Vulcano island off Sicily which in turn, was named after Vulcan, the Roman god of fire. Volcanoes are generally...
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  Sedimentary rock

  Sedimentary rock is a type of rock that is formed by sedimentation of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles (detritus) to settle and accumulate or minerals to precipitate from a...
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  Metamorphic rock

  Metamorphic rock is the result of the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat and pressure (temperatures greater than 150 to 200 °C and pressures of 1500 bars) causing profound...
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  Batholith

  A batholith (from Greek bathos, depth + lithos, rock) is a large emplacement of igneous intrusive (also called plutonic) rock that forms from cooled magma deep in the earth's crust. Batholiths are almost always made mostly of felsic or intermediate rock-types, such as granite, quartz monzonite, or...
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  Fumarole

  A fumarole (Latin fumus, smoke) is an opening in Earth's (or any other astronomical body's) crust, often in the neighborhood of volcanoes, which emits steam and gases such as carbon dioxide, sulfur dioxide, hydrochloric acid, and hydrogen sulfide. The name solfatara, from the Italian solfo, sulfur ...
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  Stratovolcano

  A stratovolcano, sometimes called a composite volcano, is a tall, conical volcano with many layers (strata) of hardened lava, tephra, and volcanic ash. Stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions. The lava that flows from stratovolcanoes tends to be...
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  Guyot

  A guyot /ɡiˈoː/, also known as a tablemount, is an isolated underwater volcanic mountain (seamount), with a flat top over 200 metres (660 feet) below the surface of the sea. The diameters of these flat summits can exceed 10 km (6 miles). The guyot was named after the Swiss-American geographer and...
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  Monadnock

  A monadnock or inselberg is an isolated rock hill, knob, ridge, or small mountain that rises abruptly from a gently sloping or virtually level surrounding plain. The term "monadnock" is usually used in the United States, whereas "inselberg" is the more common international term. In southern and...
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  Volcanic cone

  Volcanic cones are among the simplest volcanic formations in the world. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and size of the fragments ejected during...