Transcript Metamorphism - Earth Science Teachers' Association

Metamorphism
What is it ?
Meta means ‘change’
Morph means ‘form’
Activity : Look at the rocks you have – put
them in groups that make sense to you
Metamorphic Rocks
Schist
Gneiss
What is the difference ?
Watch the overhead projector
Metamorphic Rocks
Spotted Rock
Gneiss
Which one is has been
under pressure and which
not ?
Contact Metamorphism
• Changes due to the action of heat alone
• Magma rises in cracks, faults and joints
• Heat from the magma
transfers to the rock
surrounding it (called country
rock)
• The country rock then
changes and creates new
minerals - but does not melt
Regional Metamorphism
• Occurs due to progressive increase in
pressure and temperature conditions
• Related to subduction zones – very large
scale
Foliation
Contact – no layers
Regional - layers
Rocks that have been subjected to
pressure form foliations = layers
Summary
• Contact - by the action of Heat alone
• Regional - by the action of Heat and
Pressure together
• Mudrocks – change a lot : new minerals
• Sandstones and Limestones - change very
little : no new minerals, but original minerals
get bigger
Key Words
Slate
Schist
Gneiss
Marble
Foliation
Regional
Metamorphism
Unfoliated
Contact
Metamorphism