Most igneous rocks are classified as either volcanic or plutonic based on their ____.
A)size and location
B)magnesium content
C)iron content
D)texture and composition
E)size and composition

Question

Quizplus · Accepted Answer

Igneous rocks are classified as volcanic or plutonic based on their texture and composition. Volcanic rocks have a fine-grained texture because they cool quickly on the Earth’s surface, while plutonic rocks have a coarse-grained texture because they cool slowly beneath the surface. The composition of the rocks can also be used to distinguish between volcanic and plutonic rocks. Volcanic rocks tend to have higher silica content and lower iron and magnesium content, while plutonic rocks tend to have lower silica content and higher iron and magnesium content.

Most Igneous Rocks Are Classified as Either Volcanic or Plutonic