What factors influence the texture of an igneous rock? The texture in igneous rocks depends on the following four factors: i) Viscosity of magma ii) Rate of cooling iii) The order of crystallization of the constituent minerals. iv) The relative rates of growth of the constituent minerals.
Which of the following best describes Aphanitic texture?
Which of the following best describes an aphanitic texture? the rock is crystalline; mineral grains are too small to be visible without a magnifying lens or microscope.
How do you determine the texture of an igneous rock?
The texture of an igneous rock (fine-grained vs coarse-grained) is dependent on the rate of cooling of the melt: slow cooling allows large crystals to form, fast cooling yields small crystals.
What are the 4 different textures of igneous rocks?
Igneous textures are used by geologists in determining the mode of origin of igneous rocks and are used in rock classification. There are six main types of textures; phaneritic, aphanitic, porphyritic, glassy, pyroclastic and pegmatitic.
What does the texture of igneous rocks describe?
The texture of a rock refers to the details of its visible character. … There are nine main types of igneous rock textures: Phaneritic, vesicular, aphanitic, porphyritic, poikilitic, glassy, pyroclastic, equigranular, and spinifex. Each kind of texture has a variety of different characteristics that make them unique.
What best describes an aphanitic igneous rock?
Which of the following best describes an aphanitic texture? The rock contains broken fragments and is volcanic in origin. The rock has mineral grains that are glassy. The rock is crystalline, but mineral grains are too small to be seen with the unaided eye.
What are igneous rocks classified by?
Igneous rocks may be simply classified according to their chemical/mineral composition as felsic, intermediate, mafic, and ultramafic, and by texture or grain size: intrusive rocks are course grained (all crystals are visible to the naked eye) while extrusive rocks may be fine-grained (microscopic crystals) or glass ( …
How is a igneous rock formed?
Igneous rocks form when magma (molten rock) cools and crystallizes, either at volcanoes on the surface of the Earth or while the melted rock is still inside the crust.
What is the texture of extrusive igneous rocks?
The texture of extrusive rocks is characterized by fine-grained crystals indistinguishable to the human eye, described as aphantic. Crystals in aphantic rocks are small in size due to their rapid formation during eruption.
Which does not determine the texture of igneous rocks?
Pick the option which does not determine the texture of igneous rocks. … It is determined by the size, shape and arrangement of these constituents within the body of the rock.
How many different kinds of igneous rocks are there?
The two main categories of igneous rocks are extrusive and intrusive. Extrusive rocks are formed on the surface of the Earth from lava, which is magma that has emerged from underground. Intrusive rocks are formed from magma that cools and solidifies within the crust of the planet.
What is the texture of intrusive igneous rocks?
Intrusive rocks have a coarse grained texture. Extrusive Igneous Rocks: Extrusive, or volcanic, igneous rock is produced when magma exits and cools above (or very near) the Earth’s surface. These are the rocks that form at erupting volcanoes and oozing fissures.
Which term best describes igneous rocks?
Hard and dense. Which terms best describe igneous rocks: Light and easily broken, soft and smooth, hard and dense, soft and dence. From slowly cooling magma.
What is the texture of igneous rocks with crystals between 1 and 10mm?
That’s why intrusive igneous rocks usually have a coarse to very coarse texture. As you can see from the chart, coarse texture = grain sizes of 1 to 10 mm and very coarse texture = grain sizes of 10mm and larger. Granite, Diorite, Gabbro, Peridotite and Dunite are the names of the coarse grained igneous rocks.
What are the 4 textures of igneous rocks?
Igneous Rock Textures
- COARSE GRAINED TEXTURE (PHANERITIC), mineral grains easily visible (grains several mm in size or larger)
- B) FINE GRAINED TEXTURE (APHANITIC), mineral grains smaller than 1mm (need hand lens or microscope to see minerals)
- C) PORPHYRITIC TEXTURE (MIXED FINE AND COARSE)
What is an Aphanitic texture in igneous rocks?
Aphanitic is a descriptive term for small crystals, and phaneritic for larger ones. Very coarse crystals (those larger than 3 centimetres, or 1.2 inches) are termed pegmatitic. In igneous rock.
What are the 3 characteristics of igneous rocks?
Igneous rocks can be easily identified with their texture, density, colour, and mineral composition. Its texture depends on the shape, size, time period to cool down and solidify, and the arrangement of crystals in the rock.
How do you identify igneous rocks?
Igneous rocks are rocks which solidify from molten material (magma). Cooling of the magma can occur beneath the surface (plutonic) or on the surface (volcanic). Igneous rocks can be identified by the determination of the composition and texture of the rock.
What are the 4 types of igneous rocks?
Igneous rocks can be divided into four categories based on their chemical composition: felsic, intermediate, mafic, and ultramafic.
Where are igneous rocks found?
Where Igneous Rocks Are Found. The deep seafloor (the oceanic crust) is made almost entirely of basaltic rocks, with peridotite underneath in the mantle. Basalts are also erupted above the Earth’s great subduction zones, either in volcanic island arcs or along the edges of continents.
What are the 3 main types of igneous rocks?
When molten rock , or melted rock , solidifies, igneous rocks are formed. There are two types of igneous rocks : intrusive and extrusive.
…
Extrusive Igneous Rocks
- andesite.
- basalt.
- dacite.
- obsidian.
- pumice.
What is the example of extrusive igneous rock?
Extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals. Some cool so quickly that they form an amorphous glass. These rocks include: andesite, basalt, dacite, obsidian, pumice, rhyolite, scoria, and tuff.
What are characteristics of intrusive igneous rocks?
Intrusive rocks are characterized by large crystal sizes, i.e., their visual appearance shows individual crystals interlocked together to form the rock mass. The cooling of magma deep in the Earth is typically much slower than the cooling process at the surface, so larger crystals can grow.
What are the three characteristics of intrusive igneous rocks?
Characteristics of Intrusive Rocks
- Formation. Intrusive rocks are formed from magma deep in the earth. …
- Texture. Rock textures refer to crystal characteristics visible with the unaided eye. …
- Color. Igneous rocks are categorized by light, medium and dark colors. …
- Intrusive Rock Formations.
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