Igneous rock Flashcards
Igneous rock formation
Formed when lava or magma cools and crystalizes
Intrusive igneous rock
Formed when magma hardens below the surface. Cooling is much slower, resulting in large crystals in the rock
Extrusive igneous rock
Formed when lava hardens above the surface. Cooling is much faster, resulting in small crystals in the rock
How are igneous rocks classified?
Based on their composition and texture
Composition
What they are made of or the amounts of light and dark minerals in the rock
Texture
How they look based on the size, shape and arrangement of crystals
Types of texture
coarse-grained, fine-grained, glassy texture, porphyritic
Coarse-grained
Caused by slow cooling, resulting in large crystals
Fine-grained
Caused by rapid cooling, resulting in smaller crystals
Glassy texture
Caused by very rapid cooling
Porphyritic texture
A mix of both large and small crystals
Composition types
Felsic, intermediate, mafic, ultramafic
Felsic
Rocks made of mostly light-colored minerals
Intermediate
Rocks between light colored and dark colored minerals
Mafic
Made MOSTLY of dark colored silicate minerals and plagioclase feldspar
