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hot spots
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Definition
| A volcanic center located within a lithospheric plate that is thought to be caused by a plume of hot mantle material rising from depth. |
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| A volcanic belt is a large volcanically active region. Other terms are used for smaller areas of activity, such as volcanic fields. |
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volcanic island arc
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Definition
| An island arc is a type of archipelago formed as one oceanic tectonic plate subducts under another and produces magma at depth below the over-riding plate. |
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| A vent in Earth's surface through which molten rock and gases escape. The term also refers to deposits of ash and lava which accumulate around this vent. |
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| A very large intrusive igneous rock mass that has been exposed by erosion and with an exposed surface area of over 100 square kilometers. A batholith has no known floor. |
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| A dike in geology is a type of sheet intrusion referring to any geologic body that cuts discordantly across. |
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| A term used to describe an igneous rock that has a large percentage of light-colored minerals such as quartz, feldspar, and muscovite. Also used in reference to the magmas from which these rocks crystallize. Felsic rocks are generally rich in silicon and aluminum and contain only small amounts of magnesium and iron. Granite and rhyolite are examples of felsic rocks. (See mafic to contrast.) |
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| An igneous intrusion that has been forced between two layered rock units. The top of the intrusion is arched upwards and the bottom of the intrusion is nearly flat. |
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| Molten rock material on Earth's surface. |
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| A term used to describe an igneous rock that has a large percentage of dark-colored minerals such as amphibole, pyroxene and olivine. Also used in reference to the magmas from which these rocks crystallize. Mafic rocks are generally rich in iron and magnesium. Basalt and gabbro are examples of mafic rocks. (See felsic to contrast.) |
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| Molten rock material that occurs below Earth's surface. |
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| A pluton in geology is an intrusive igneous rock (called a plutonic rock) body that crystallized from magma slowly cooling below the surface of the Earth. |
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| Rift eruptions are volcanoes that occur where magma erups through long cracks in the lithosphere where tectonic plates are spreading apart. |
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| a sill is a tabular pluton that has intruded between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. |
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| a stock is a discordant igneous intrusion having a surface exposure of less than 40 square miles, differing from batholiths only in being smaller. |
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