Chapter 7
Chapter 7: Metamorphism: A Process of Change
Animation
This animation shows how squeezing or shearing a rock under metamorphic conditions can result in preferred mineral orientation. Inequant grains distributed through a soft matrix rotate into parallelism as the rock changes shape. For more information, see “Foliated Metamorphic Rocks” starting on p. 180 and Figure 7.4 in your textbook.
A glaciated surface exposing gneiss contains alternating bands of light-colored and dark-colored minerals. A geologist’s interpretation of the outcrop emphasizes the banding.For more information, see “Gneiss” starting on p. 181 and Figure 7.6a in your textbook.
Metamorphic rocks form when a preexisting rock (a protolith) undergoes changes in texture and/or mineral content in the solid state, in response to changes in temperature, pressure, or differential stress, or in response to interactions with hydrothermal fluids. For more information, see 7.6 Where Do You Find Metamorphic Rocks? starting on p. 191 and Geology at a Glance: Environments of Metamorphism on p. 188 in your textbook.