Where does Igneous activity occur Igneous activity occurs in four plate

Where does igneous activity occur igneous activity

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Where does Igneous activity occur - Igneous activity occurs in four plate-tectonic settings o Volcanic arcs bordering deep ocean trenches o Isolated hot spots o Continental rifts o Mid-ocean ridges - Established or newly formed tectonic plate boundaries - Except: hot spots, which are independent of plates. Volcanic arcs - Most subaerial volcanoes on Earth reside in arcs - Mark convergent tectonic plate boundaries o Deep oceanic trenches and accretionary prisms o Subducting oceanic lithosphere adds volatiles (water) o Rocks of the asthenosphere partially melt o Magma rises and creates volcanoes on overriding plate o Magma may differentiate Hot Spots
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- About 50-100 mantle plume hot spot volcanoes exist - Independent tectonic plate boundaries - May erupt through oceanic or continental crust o Oceanic – mostly mafic magma (basalt) o Continental – mafic or felsic (basalt or rhyolite) - Burn a volcano chain through overriding tectonic plate o Creates a hot spot track Continental rifts - Places where the continental lithosphere is being stretched - Rifting thins the lithosphere o Causes decompressional melting of mafic rock o Heat transfer melts crust, creating felsic magmas Mid-ocean ridge - Most igneous activity happens at mid-ocean ridges o Rifting spreads plates leading to decompression melting o Basaltic magma wells up and fills magma chambers o Solidifies as gabbro at depth o Moves upward to form dikes or extrude as pillow basalt Large Igneous Provinces - LIPS – unusually large outpouring of magma o Mostly mafic, include some felsic examples o Mantle plume first reaches the base of the lithosphere o Erupts huge volumes of mafic magma as flood basalts Low viscosity Can flow tens of hundreds of kms Accumulate in thick piles
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