Organizing Metamorphic Rocks
Metamorphism: the process that creates metamorphic rocks.
All made from the alteration of existing rocks by excessive…
pRESSURE
AND/OR
The most obvious effect is the
rearrangement of minerals grains
into bands or stripes called
foliations.
hEAT
Temperatures above 200oC will
create new minerals in the rock or
will enlarge existing minerals known
as recrystallization
Two types of MR: sorted by texture
1. Foliated – bands or stripes
The mineral grains in rocks
subjected to extreme pressure
often rearrange themselves in a
parallel fashion.
2. Non-Foliated - no particular direction
Examples:
Foliated –
Non-Foliated –
How does metamorphism happen?
What force has the power to squish & heat rocks until the crystals change?
Regional Metamorphism
Occurs over large areas (as big as states or countries!) Existing
rock will change by the heat and pressure created during mountain
building.
(A) continents collide
(B) ocean crust subducts
How does metamorphism happen?
What force has the power to squish & heat rocks until the crystals change?
Contact metamorphism
Occurs over small areas. Existing rock is heated when it comes
in contact with magma or lava.
This sill baked the
adjoining limestone into
marble.
The lava flow (in gray)
seen in this road cut has
baked the mud beneath it
into brick.
Rock
Type
SR
MR
MR
MR
SR
SR
IR
IR
Parent Rock
Metamorphic Rock
Shale
Slate
Phyllite
Schist
Sandstone
Limestone
Basalt
Granite
Slate
Phyllite
Schist
Gneiss
Quartzite
Marble
Schist
Gneiss