Download Metamorphic Rocks

Metamorphic Rocks
Metamorphism
• Preexisting rocks change form
• Rocks that are the result of
metamorphism often look very different
from the parent rock (rock you start
with)
• Occurs at high temperature and
pressure—from a few kilometers down
to the upper mantle
Two Types of Metamorphism
Contact Metamorphism
• Also called low grade metamorphism
• Occurs when magma intrudes (pushes
into) rock
• Causes only minor changes in rocks
• Ex: Marble forms when magma intrudes
into limestone.
Regional Metamorphism
• Also called high grade metamorphism
• Occurs during mountain building events
• Results in large scale deformation of
rocks (big changes)
• Ex: folded rocks
Agents of Metamorphism
• Heat—most important agent, comes
from magma and increasing depth within
Earth, “bake” rocks and minerals change
• Pressure—stress, like heat increases
with depth, rocks flatten and flow,
mountain building
• Hydrothermal solutions—hot waterbased solutions dissolve original
minerals and deposit new ones
Classification of Metamorphic
Rocks
• Like igneous rocks based on texture and
composition
Texture
Foliated
Nonfoliated
•Banded appearance
•Do not have banded
texture
•Example: gneiss
(pronounced nice)
•Ex: marble, quartzite