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Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form intrusions, such as batholiths, dikes, sills, laccoliths, and volcanic necks. [1] [2] [3] Intrusion is one of the two ways igneous rock can form. The other is extrusion, such as a volcanic eruption or similar event.
Volcanic necks are feeder pipes for volcanoes that have been exposed by erosion. Surface exposures are typically cylindrical, but the intrusion often becomes elliptical or even cloverleaf-shaped at depth. Dikes often radiate from a volcanic neck, suggesting that necks tend to form at intersections of dikes where passage of magma is least ...
In geology, a sill is a tabular sheet intrusion that has intruded between older layers of sedimentary rock, beds of volcanic lava or tuff, or along the direction of foliation in metamorphic rock. A sill is a concordant intrusive sheet, meaning that it does not cut across preexisting rock beds.
A dike of lamprophyre near the Shiprock volcanic plug, New Mexico, that has resisted the erosion that removed some of the softer rock into which the dike was originally intruded. A magmatic dike is a sheet of igneous rock that cuts across older rock beds. It is formed when magma fills a fracture in the older beds and then cools and solidifies.
Basic types of intrusions: 1. Laccolith 2. Small dike 3. Batholith 4. Dike 5. Sill 6. Volcanic neck, pipe 7. Lopolith As a general rule, in contrast to the smoldering volcanic vent in the figure, these names refer to the fully cooled and usually millions-of-years-old rock formations, which are the result of the underground magmatic activity shown.
Satellite image of the Big Raven Plateau in British Columbia, Canada Rangipo Desert of the North Island Volcanic Plateau. Numerous tephra layers are visible. The Pajarito Plateau in New Mexico, United States is an example of a volcanic plateau. A volcanic plateau is a plateau produced by volcanic activity. There are two main types: lava ...
An extensional environment is inferred by the presence of sheeted dikes. Geologists have debated the origins of keratophyres, suggesting a back-arc basin environment, although this is challenged by high-levels of silica in the rocks. Local hydrothermal alteration was proposed as a reason for metal anomalies in the Lameshur Volcanic-Intrusive ...
Volcanic rock types found on the Canary Islands are typical of oceanic islands. The volcanic rocks include alkali basalts, basanites, phonolites, trachytes, nephelinites, trachyandesites, tephrites and rhyolites. [19] [3] There are lava flows as well as deposits of pyroclastic material, such as tuff (made of volcanic ash or lapilli).