Metamorphic Rock
Rocks that have changed their-structure,
texture, or composition
Rocks were changed due to heat, pressure
or a combination
Origins of Metamorphic Rock
• When surroundings of rock change so will the
• Temperature is between 50-1000C, rocks melt
• Metamorphic rock also need pressure and
depth to change
• Earth crust moving helps create this pressure
besides the depth
Contact Metamorphism
• When magma moves through earth layers, it
heats rocks around it-may cause some of them
to change
• Pg. 107- Figure 2
Regional Metamorphism
• When pressure builds up or crust collide
• Happens deep in the Earth
Composition of Meta. Rock
• Index minerals- are minerals that change at
certain temperatures and pressures
– Ex- biotite mica, chlorite, garnet, kyanite,
muscovite mica, sillimantie, and staurolite
Texture of Meta. Rock
• Foliated
– Mineral grains are arranged in planes or bands
– Ex. Slate—phyllite—schist---gneiss (this all
happens when more heat and pressure is added)
• Nonfoliated
– Mineral grains are NOT arranged in planes/bands
– Crystals-can change the size or minerals its made
off= recrystallization
• Ex. Quartzite- is shiny, glittery appearance
– Crystals have gotten larger
– Limestone can due this and become Marble
Metamorphic Rock Structures
• Deformations
– Change in the shape of a rock caused by force
placed on it
– Usually see it squeezed, stretched, fold, or bends

Metamorphic Rock - Treynor Community Schools