Earth Science 4.13 and 4.14

4.13 Metamorphic Rocks
4.14 Metamorphic Rock Classification

Introduction to Metamorphism

• Metamorphism: The process of changing one type of rock into another
• Starting rock can be igneous, sedimentary, or metamorphic
• Caused by heat and/or pressure
• Changes can be physical, chemical, or both
• Results in the formation of metamorphic rocks

Multiple Choice

Any rock formed when another rock is changed by heat or __________ is a metamorphic rock.

• pressure
• arrangement

Chemical Changes in Metamorphism

• Ion movement within minerals
• Formation of new, more stable minerals
• Example: Limestone (CaCO₃) → Marble (recrystallized CaCO₃)
• Process depends on temperature, pressure, and chemical environment

Multiple Choice

The metamorphic rock __________ usually forms when limestone is subjected to heat and pressure deep beneath the surface.

• marble
• slate
• sandstone

Physical Changes in Metamorphism

• Foliation: Formation of layers due to directional pressure
• Non-foliated rocks: Result of uniform pressure from all directions
• Examples:

• Foliated: Slate, gneiss

• Non-foliated: Marble, quartzite

Types of Metamorphism

1. Contact Metamorphism
   • Occurs when magma contacts a rock
   • Localized, high-temperature changes
   • Example: Formation of hornfels

2. Regional Metamorphism
   • Affects large areas of rock
   • Caused by deep burial or tectonic compression
   • Example: Formation of gneiss

Multiple Choice

Heat and pressure change the sedimentary rock shale into slate.

• true
• false

Multiple Choice

Because the foliated metamorphic rock __________ splits easily into flat pieces, it is used for roofing material.

• marble
• slate
• sandstone

Summary

• Any type of rock—igneous, sedimentary, or metamorphic—can become a metamorphic rock.

• Contact metamorphism occurs when a rock is altered by heat from nearby magma.

• Regional metamorphism occurs over a large area when a rock is buried or compressed.

Summary