Rock Cycle
Foliation & Rock Types
Metamorphism
100
What processes form sedimentary rock?
Weathering - to break it into sediment
Erosion - to transport that sediment to a basin
Compaction & Cementation - to turn the sediment to stone
100
What conditions produce low grade and high grade metamorphism?
Bonus: What are the other names for "Low" and "High" foliation?
low temp, low pressure = low grade / "slatey"
high temp, high pressure* = high-grade / "gneissic"
*by rock standards, still very high
100
What kind of metamorphism is happening to the rocks in the blue area?
Contact metamorphism
200
What rocks can turn into igneous rock? How?
Any of our main 3 (Igneous, Meta, Sedimentary) can form an igneous rock if they are melted and then freeze(crystallize).
200
What does foliation look like in a rock?
Layers
200
True or false: Metamorphic rocks are rocks that have been partially melted.
FALSE
Metamorphic rocks NEVER melt. Heat may cause crystals to recrystalize into new structures or minerals, but they don't melt.
They may get so close that minerals can migrate within the rock, which is how felsic and mafic minerals come together to make light and dark bands in Gneissic Banding/High Grade Foliation in the highest temperature and pressure metamorphic rocks, BUT, they never actually melt.
300
If a metamorphic rock is:
1. buried deep underground
2. Exposed to heat and pressure as two continents collide and raise enormous mountains
What kind of rock would it be now?
(One word)
Bonus: What kind of metamorphism is this?
metamorphic - maybe much more metamorphosed than the original rock, but still metamorphic
This would be regional metamorphism, rocks being changed by heat and pressure in a tectonic collision, like what is happening in the Himalayas right now.
300
What causes foliation?
Bonus: What kind of metamorphism *doesn't* produce foliation?
Pressure!
Contact metamorphism is all about heat so it doesn't typically produce foliation.
It doesn't produce a layered or laminated texture, but instead gives a more sugary texture.
Example: Quartzite, note the sugary texture
300
Which kind of metamorphism focuses on heat alone, not pressure?
Contact Metamorphism, which occurs when magma punches through rock and the heat alters the crystal structure of the surrounding rock, without actually melting it.
On the diagram below (there is a similar one in your notes packet) contact metamorphism would be at the top right - where we have heat, but not pressure.
400
What kind of metamorphism produces fractured, folded, wavy rocks?
Regional
400
What is the difference between medium grade and high grade metamorphism?
Gneissic banding - high grade foliated rocks get alternating light and dark bands, formed when felsic (light) and mafic (dark) minerals migrate towards one another, on a molecular scale, within the rock. This can only happen the rock is really hot, so the formation of these bands is our divide between medium-grade and high-grade metamorphism.
400
Heat and pressure, together result in what kind of metamorphism?
Regional Metamorphism, which typically occurs at convergent plate boundaries.
500
Gneiss can be formed from which two kinds of parent rock?
Shale and Granite (or a lower grade metamorphic rock derived from either of those).
500
What is foliation? (What is changing in the rock?)
Minerals are being rotated to all align in flat (or flat-ish) planes perpendicular to the pressure being applied.
500
What kind of metamorphism might be happening to the rocks in the middle of this picture?
Regional Metamorphism