Structure of Igneous Rocks

M.RAJASEKHAR ASST.PROFESSOR

DEPARTMENT OF CIVIL ENGINEERING KUPPAM ENGINERING COLLEGE, KUPPAM

Structures of igneous rocks are classified into different types based upon the solidification of magma they are

1. Vesicular structures2. Amygloidal structures3. Block lava structures4. Ropy lava structures5. Pillow structures etc

Structure of Igneous Rocks

Vesicular structuresFormation of cavities in the process of cooling and crystallizations ( Due to lava rich in gases) When they escapes forming cavities in rocks

Cavities is known as vesicles these type of structures is known as vesicular structures

Amygoidal structures

After the formation of vesicles on the structure of lava they are filled by the secondary minerals like calcite or zeolite. The vesicles are called amygdaoidales. The total structure is known as amygdaoidal structures.

Block lava structuresBlock Lava is less mobile i.e. more viscous and has a Rough and irregular surface. When cools down it result into angular, chunky texture. This causes the lava to thicken and to break apart as the flow continues to move down slope.

Ropy lava structures

Ropy Lava: is more mobile i.e. less viscous, it has a wrinkled but smooth and shiny surface on cooling. .

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Ropy Lava: is more mobile i.e. less viscous, it has a wrinkled but smooth and shiny surface on cooling.

Vesicles are more in number, small-spherical in shape.

Pillow structures

Development of bulbous, overlapping, pillow like structures in the body of Igneous rock.

Lava during the under water volcanic conditions