What are the characteristics of extrusive igneous rocks?
Answers
Igneous rocks form from the solidification of magma (molten rock). A reminder: magma is molten rock beneath the Earth's surface and lava is magma that is on the Earth's surface. The main characteristics of an Igneous rock are crystal size (grain size) and texture.
Answer:
Extrusive or volcanic rocks:
These rocks are formed when magma breaks through the crust and reaches the surface of the earth (where it is called lava). It cools rapidly and solidifies to form rocks. The common rocks formed in this manner are basalt and obsidian.
Instrusive or plutonic rocks:
These rocks are formed when magma fails to break through the crust and cools slowly under the crust forming rocks. Because of slow cooling it solidifies into rocks with large grains of crystals. The common eg of rocks formed in this manner are granite and dolerite.
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