A laccolith is an igneous intrusion (or concordant pluton) that has been injected between two layers of sedimentary rock. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock In Geology, an intrusion is a body of Igneous rock that has Crystallized from molten Magma below the surface of the Earth. A pluton in Geology is an Intrusive Igneous rock body that crystallized from a Magma slowly cooling below the surface of the Earth Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock) The pressure of the magma is high enough that the overlying strata are forced upward, giving the laccolith a dome or mushroom-like form with a generally planar base. Magma (Plurals magmas and magmata) is molten rock that sometimes forms beneath the surface of the Earth (or any other Terrestrial planet

A laccolith intruding into and deforming strata

Laccoliths tend to form at relatively shallow depths and are typically formed by relatively viscous magmas, such as those that crystallize to diorite, granodiorite, and granite. Diorite (ˈdaɪəraɪt is a grey to dark grey intermediate intrusive Igneous rock composed principally of Plagioclase Feldspar (typically Granodiorite (ˌgrænəˈdaɪəraɪt/ /ˌgreɪn- is an intrusive Igneous rock similar to Granite, but contains more Plagioclase than Potassium feldspar Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. Cooling underground takes place slowly, giving time for larger crystals to form in the cooling magma. The surface rock above laccoliths often erodes away completely, leaving the core mound of igneous rock. The term was first applied as laccolite by Grove Karl Gilbert after his study of intrusions of diorite in the Henry Mountains of Utah in about 1875. Grove Karl Gilbert ( May 6, 1843 &ndash May 1, 1918) known by the abbreviated name G Diorite (ˈdaɪəraɪt is a grey to dark grey intermediate intrusive Igneous rock composed principally of Plagioclase Feldspar (typically The Henry Mountains are located in the southeastern portion of the U

It is often difficult to reconstruct shapes of intrusions. For instance, Devils Tower in Wyoming was proposed to be the remnants of an ancient laccolith. Devils Tower ( Lakota: Mato Tipila, which means “Bear Tower” is a Monolithic igneous Intrusion or Volcanic The State of Wyoming ( is a sparsely populated state in the western region of the United States. The rock would have had to cool very slowly so as to form the slender pencil-shaped columns of phonolite porphyry seen today. Phonolite is an evolved lava which is considered as forming in shallow Magma chambers Phonolite is an igneous, volcanic ( Extrusive) rock Porphyry is a variety of Igneous rock consisting of large-grained Crystals such as Feldspar or Quartz, dispersed in a fine-grained However, erosion has stripped away the overlying and surrounding rock, and so it is impossible to reconstruct the original shape of the igneous intrusion; that rock may not be the remnant of a laccolith. At other localities, such as in the Henry Mountains and other isolated mountain ranges of the Colorado Plateau, some intrusions demonstrably have shapes of laccoliths. The Henry Mountains are located in the southeastern portion of the U The Colorado Plateau, also called the Colorado Plateaus Province, is a physiographic region of the Intermontane Plateaus, roughly centered on the The small Barber Hill syenite-stock laccolith in Charlotte, Vermont USA, has several volcanic trachyte dikes associated with it. Syenite is a coarse-grained intrusive Igneous rock of the same general composition as Granite but with the Quartz either absent or present in relatively Charlotte is a town in Chittenden County, Vermont, United States. Trachyte is an Igneous, Volcanic rock with an Aphanitic to Porphyritic texture Molybdenite is also visible in outcrops on this exposed laccolith. Molybdenite is a mineral of Molybdenum disulfide, Mo[[sulfur S]]2

See also

• Batholith
• Dike
• Sill

References

• Blatt, Harvey and Robert J. A batholith (from Greek bathos, depth + lithos, rock is a large emplacement of Igneous intrusive (also called plutonic rock that forms A dike or dyke in Geology is a type of Sheet intrusion referring to any geologic body that cuts Discordantly ' across planar In Geology, a sill is a tabular Pluton that has intruded between older layers of Sedimentary rock, beds of Volcanic Tracy, 1996, Petrology: Igneous, Sedimentary and Metamorphic, 2nd ed. , pp. 13-15, Freeman, ISBN 0-7167-2438-3
• Jules D. Friedman and Curtis Huffman, Jr. , coordinators, Laccolith Complexes of Southeastern Utah: Time of Emplacement and Tectonic Setting -- Workshop Proceedings, United States Geological Survey Bulletin 2158, 1998. http://pubs.usgs.gov/bul/b2158/B2158.pdf