Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

What does foliation in rocks indicate?

1. Formation from volcanic activity

2. Presence of specific mineral types

3. Alteration due to high pressure from various directions

4. Layering due to sediment deposition

The correct answer is: Alteration due to high pressure from various directions

Foliation in rocks is a characteristic that indicates a specific type of metamorphic structure where mineral grains are aligned and can develop into a banded or layered appearance. This phenomenon primarily results from the alteration of rocks due to high pressure and directional stress, often occurring deep within the Earth's crust. The intense pressure causes the minerals to recrystallize and realign themselves in response to the forces acting upon them, leading to the formation of thin layers or bands in the rock. The presence of foliation indicates that the rock has undergone metamorphism, rather than being formed from volcanic activity, which would generally lead to a different texture, or sediment deposition, which would create sedimentary layering. While specific mineral types may be associated with foliation, the defining factor is the environmental conditions that cause the reorganization of the mineral structure due to high directional pressure.