Magma cools and solidifies can be below or above the earth's surface. When frozen below the earth's surface, forming the so-called igneous rocks or igneous intrusive in. And often also said to be a plutonic igneous rock. Meanwhile, when the magma can reach the earth's surface and then freezes, it forms igneous outside or extrusive igneous rock.
Igneous rock inner
Magma that solidifies below the earth's surface, cooling is very slow (can be up to millions of years), enabling the growth of large crystals and perfect shape, the body of intrusive igneous rock. Igneous body in shape and size has varied, depending on the conditions of magma and surrounding rocks. Magma can infiltrate the surrounding rocks, or break through the cracks, cracks in the rocks around it. In Figure 1.1. visible cross-section diagram of plutonic rock bodies. The forms are cut structure of the surrounding rocks, discordant, is batolit, stock, dyke (excavation) and levels of volcanic (volcanic neck).
While the shape is parallel to the structure of the surrounding rock, konkordan, is the sill, and lopolit lakolit.
Batolit, an igneous body in (plutons) greatest dimension. Irregular shape, cut the layers of rock that diterobosnya. Most batolit a mass gathering of a number of intrusive bodies that berkomposisi somewhat different. This difference reflects the variation of magma forming batolit. Some batolit reached more than 1000 km in length and 250 km wide. Of geophysical measurements and research on some batolit the exposed surface, the thickness is estimated between 20 to 30 km. Batolit not formed by magma that infiltrate the fracture, because there is no fracture of dimension batolit. And because of the large rocks batolit can drive on it. Although the rocks are intruded can be pressured upward by magma moving upwards slowly, surely there is another process that works. Magma that rises off the fragments of rock that covered it. This process is called stoping. The blocks of stoping denser than the magma that rises, so the precipitate. When the precipitate these fragments react and partially dissolved in the magma. But not all dissolved and precipitate at the bottom of the magma chamber (magma chamber). Every rock fragments that are in the body of magma that has been frozen named xenolith.
Stock, like batolit, irregular shape and dimensions smaller than batolit, not more than 10 km. Stock is accompanying an upper body batolit batolit or eroded.
Dike or excavation, also called the alley, is one of the intrusive rocks are compared with batolit, small dimension. The shape is tabular, as both sides parallel to the sheet, cutting structures (bedding) rocks, Figure 1.2.
Volcanic neck (level volcanics), is the pipe under the volcano crater, the magma to lava flows. Then, after covering the surrounding rock eroded, then the igneous rock that looks more or less cylindrical and protrude from the surrounding topography is called a volcanic level.
Sill is the intrusion of igneous rock that konkordan or parallel to the bedding rock diterobosnya. Tabular-shaped with parallel sides.
In general there is a dike and sill the same time, is part of a system of intrusive rocks, drawing 1.2. Dike and sill can be very large. For example the Great Dike in Zimbabwe, Africa, is a gabbro mass of 500 km and 8 km wide, with walls walls are parallel and straight.
While there are examples of large sill near the city of New York, United States, on the cliff S. Hudson, its thickness is approximately 300 meters.
Lakolit intrusion similar to the sill is parallel to the bedding rock. Distinguished because the shape of the upper sill, rock diterobosnya or convex curved upwards, forming a gently sloping dome. While the bottom is similar to the sill. As a result of geological processes, either by force of endogenous, exogenous and style, in igneous rocks can be exposed or floating above the earth's surface. Although formed beneath the surface of the earth, lifted by tectonic forces,
Figure 1.1. Cross-sectional diagram of igneous rock in. Batolit-body of igneous rock which is very large, irregularly-shaped and basically unknown; stock-a small body and is equal to batolit; dyke-excavation or alley, which cut the plate-shaped structure surrounding rocks; sill-shaped together with the dyke, but parallel to the surrounding structures; lakolit together with the sill, the top convex upwards. Many igneous rocks in the volcano-related (Skinner, 2004).
Figure 1.2 Dike and sill is an intrusive rock bodies shaped flat (tabular). Dike cut the surrounding rock layers. Sill is injected between the layers of rock. (WK. Hamblin, 1989).
and eroded rock layers above it, so that the igneous rocks in the surface. Although today we see already above the earth's surface, they are still included in due to the formation of igneous rocks under the surface.
Lopolit shaped like the lakolit, only the top and bottom concave upwards.
Igneous rocks in addition to having various forms of intrusion of the body, there are also different types of rocks, based on the composition of its constituent minerals. Of the richest in minerals kuarsanya until at least the granite and granodiorite, diorite, gabbro and peridotite, as seen in the rock column in the table Faneritik Classification of Frozen Rocks.
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