5 Questions
What is the primary difference between intrusive and extrusive igneous rocks?
The rate of cooling of the magma
Which of the following statements about the classification of igneous rocks is true?
Igneous rocks are classified based on their mineral composition
What is the reason for the difference in texture between phaneritic and aphanitic rocks?
The difference in the rate of cooling
Which type of igneous rock is characterized by a porphyritic texture?
Andesite
What is the primary factor that determines the composition of an igneous rock?
The type of minerals present in the magma
Study Notes
Igneous Rocks
- Intrusive vs Extrusive Igneous Rocks: The primary difference lies in their formation; intrusive rocks form below the Earth's surface (cooler, slower cooling), while extrusive rocks form above the surface (hotter, faster cooling).
Classification of Igneous Rocks
- True Statement: Igneous rocks are classified based on their mineral composition and texture.
Texture of Igneous Rocks
- Phaneritic vs Aphanitic Textures: The difference in texture is due to the rate of cooling; phaneritic rocks cool slowly, allowing for large crystals to form, while aphanitic rocks cool quickly, resulting in small crystals.
Porphyritic Texture
- Characteristics of Porphyritic Rocks: This type of rock is characterized by having large crystals (phenocrysts) embedded in a finer-grained matrix.
Composition of Igneous Rocks
- Factors Affecting Composition: The primary factor determining the composition of an igneous rock is the type of magma (molten rock) from which it forms, influenced by the source of the magma and the processes that occur during its ascent and cooling.
Test your knowledge on the formation and classification of igneous rocks, including intrusive and extrusive types, textures, and composition.
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