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Is porphyritic texture intrusive or extrusive?

Porphyritic texture — andesite: This is an extrusive igneous rock. The magma from which it formed cooled slowly for a while deep below the surface (forming the large crystals), then finished cooling very quickly when it was ejected at the surface, forming the fine-grained groundmass.

What is the texture of an intrusive igneous rock?

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 ( …

What process forms rocks with porphyritic texture?

A porphyritic texture is developed when magma that has been slowly cooling and crystallising within the Earth’s crust is suddenly erupted at the surface, causing the remaining uncrystallised magma to cool rapidly. This texture is characteristic of most volcanic rocks.

What type of rocks are intrusive and extrusive?

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.

What are the similarities between intrusive and extrusive rocks?

Intrusive and extrusive igneous rocks are alike in that they are both formed from the cooling and crystallization of molten substance (magma and lava,…

How do you know if an intrusive and extrusive rock is apart?


  1. Intrusive igneous rocks cool from magma slowly in the crust. They have large crystals.
  2. Extrusive igneous rocks cool from lava rapidly at the surface. They have small crystals.
  3. Texture reflects how an igneous rock formed.

How would you know if it is an intrusive or extrusive rock?

Intrusive igneous rocks cool from magma slowly because they are buried beneath the surface, so they have large crystals. Extrusive igneous rocks cool from lava rapidly because they form at the surface, so they have small crystals. Texture reflects how an igneous rock formed.

What factors influence the texture of an igneous rock?

Texture of igneous rocks defines the shape, size and mutual relationship of the constituent minerals. 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.

What factors influence the texture of an igneous rock quizlet?

The texture of an igneous rock is determined by the cooling history of the magma from which it formed. Magmas that cool slowly form large crystals, and those that cool quickly form small crystals. Define phaneritic texture. Phaneritic texture describes coarse grained rocks.

What factors can affect the texture of a sedimentary rock?

Textures of Sedimentary Rocks

  • The strength of the wind or water currents that carry and deposit the sediment.
  • The distance transported or time in the transportation process.
  • Biological activity with the sediment prior to diagenesis.
  • The chemical environment under which diagenesis occurs.

What are the six major igneous rock textures?

Igneous textures include the rock textures occurring in igneous rocks. Igneous textures are used by geologists in determining the mode of origin igneous rocks and are used in rock classification. There are six main types of textures; phaneritic, aphanitic, porphyritic, glassy, pyroclastic and pegmatitic.

How do you describe the texture of a rock?

The texture of a rock is the size, shape, and arrangement of the grains (for sedimentary rocks) or crystals (for igneous and metamorphic rocks). Also of importance are the rock’s extent of homogeneity (i.e., uniformity of composition throughout) and the degree of isotropy.

What are some examples of an igneous rock?

These rocks include: andesite, basalt, dacite, obsidian, pumice, rhyolite, scoria, and tuff. Pictures and brief descriptions of some common igneous rock types are shown on this page.

What are the three 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….Igneous Rocks

  • diorite.
  • gabbro.
  • granite.
  • pegmatite.
  • peridotite.

What is a fun fact about igneous rock?

Interesting Igneous Rocks Facts: When magma rises to the surface of the Earth and hardens, it forms extrusive igneous rock. Extrusive igneous rock tends to be glassy in texture because their formation occurs very rapidly. Examples of extrusive igneous rock include pumice and basalt.

What are some key features of igneous rocks?

Characteristics of Igneous Rocks

  • The igneous form of rocks does not include any fossil deposits.
  • Most of the igneous forms include more than one mineral deposit.
  • They can be either glassy or coarse.
  • These usually do not react with acids.

How can you identify an igneous rock?

Examine your rock for signs of visible grains. Igneous rocks are very dense and hard. They may have a glassy appearance. Metamorphic rocks may also have a glassy appearance. You can distinguish these from igneous rocks based on the fact that metamorphic rocks tend to be brittle, lightweight, and an opaque black color.