Herricks High School Earth Science Metamorphic Rocks Herricks High School Earth Science

Metamorphism The changes that occur in solid rock due to great temperature, great pressure, and chemical activity.

Three Factors of Change Heat Pressure Chemical Activity

Metamorphism Parent Rock- the preexisting rock from which a metamorphic rock forms Parent Rock -------------- Metamorphic

Types of Metamorphism Regional Metamorphism: occurs over large areas and is associated with mountain building Deeply buried igneous and sedimentary rocks are squeezed by the weight of rock layers above Examples: Slate, Phyllite, Schist, Gneiss

Regional Metamorphism

Contact Metamorphism Contact Metamorphism: occurs when molten rock comes into contact with surrounding rocks

How do metamorphic rocks change? 1. Crystalline Texture: Recrystallization Under heat and pressure the size, shape, and spacing of grains change. Rock may partially melt and fuse together forming larger crystals or pressure may break grains into smaller pieces, destroying the original texture of the rock

How do metamorphic rocks change? (con’t) 2. Increased Density: Pressure from deep burial closes pore spaces in sedimentary rocks and openings in igneous Its mass is forced into a smaller volume, and its density increases.

Visual Characteristics of Metamorphic Rocks Foliation: results when mineral grains recrystallize or are flattened under pressure A rock is said to be foliated when its crystals are arranged in layers or bands along which the rock breaks easily. Example: foliation of gneiss

Visual Characteristics (con’t) Banding: occurs when minerals of different densities recrystallize under pressure and separate into layers Like oil and water Alternate light and dark (light being less dense than dark)

Banding gneiss

Visual Characteristics (con’t) Distortion of Layers: When layers of rock become metamorphosed, twisting and contorting could occur. These distortions are commonly seen in large-scale outcrops.

Distortion

Roman Forum, Roma, Italy 7/29/2011 Name That Rock! Location: Roman Forum, Roma, Italy 7/29/2011

Erosion Transportation Heat, pressure, stress Magma (molten rock) Weathering Deposition Igneous rock Granite, pumice, basalt Sedimentary rock Sandstone, limestone Heat, pressure Cooling Heat, pressure, stress Magma (molten rock) Figure 15.8 Natural capital: the rock cycle is the slowest of the earth’s cyclic processes. The earth’s materials are recycled over millions of years by three processes: melting, erosion, and metamorphism, which produce igneous, sedimentary, and metamorphic rocks. Rock from any of these classes can be converted to rock of either of the other two classes, or can be recycled within its own class. QUESTION: List three ways that the rock cycle benefits your lifestyle. Melting Metamorphic rock Slate, marble, gneiss, quartzite Fig. 15-8, p. 343 17

The Rock Cycle: The Story of “Herbie”