The Rock Cycle Flashcards
What is a mineral
A naturally occurring, inorganic, crystalline solid
Specific chemical composition
What are rocks? What are outcops/exposures?
Coherent and naturally occurring
- aggregate of one or more minerals
Outcrop/Exposure = exposed rock surfaces
What is granite made of?
Made up of Plagioclase feldspar, quartz, potassium feldspar, and biotite
Explain silicate minerals and carbonate minerals (2 types of rock forming minerals)
examples?
Silicate minerals:
- SiO4 tatrahedra
- ~30% of all known minerals
- 90% of Earth’s crust
- ex. quartz, potassium feldspar
Carbonate minerals:
- CO3
- ex. calcite: most common non-silicate > main component of animal shells and skeletons
What are igneous rocks?
What are the two types of igneous rocks? what are these classified by?
Rocks that form when molten rock, or magma, cools and solidifies
Extrusive (volcanic)
- rapid cooling on or near earth’s surface
- aphanitic > fine-grained texture that is too small to see without magnification
(rhyolite, andesite, basalt)
Intrusive (plutonic)
- slow cooling deep within the earth
- phaneritic > large crystals that are visible to the naked eye
(granite, diorite, gabbro)
Which Igneous rock has a porphyritic texture? What does this mean?
Andesite
> 2 stage cooling - slow cooling stars in the magma chamber and then sudden eruption which causes the rest to cool rapidly
> large crystals are set in a finer-grained matrix
*porphyritic rocks are porphyrys
How are igneous rocks mostly classified?
Most igneous rocks are classified by composition and texture
Composition: felsic or mafic
> main component of magma is silica > different percentages of silica determine composition >
felsic = most silica (lighter elements and typically lighter in colour)
mafic = least silica (heavier elements and typically darker colour)
Texture:
vesicular - gas bubbles (ex. pumice and scoria)
glassy - cools quickly (ex. obsidian) pyroclastic or fragmental - ash (ex. tuff)
Compare pumice and scoria
Both igneous rocks with vesicular texture
- pumice is glassy and its density is so low that it floats > felsic composition
- scoria is darker, heavier, and more crystalline > mafic composition
What are sedimentary rocks and how are they formed and where do these processes take place? How is sediment transported?
Any rocks made up of sediment
Formed by:
- weathering, erosion
- precipitation of minerals from solution
- compaction of plant and animal remains
> processes take place at the surface
Sediment is transported by water, glaciers, and wind
Explain the lithification process of sedimentary rocks
- sediments accumulate
- sediments become compacted by weight
- sediments are cemented by minerals
What are the relative particle sizes of gravel, sand, silt, and clay?
gravel > 2mm
sand 1/16-2mm
silt 1/256-1/16mm
clay <1/256mm
What are detrital sedimentary rocks? example?
- composed of clasts
- clasts = weathered fragments of pre-existing rocks
> made up of different sizes of sediments (gravel, sand, silt, clay)
ex. sandstone (made from sand grains that come from the breaking down of pre-existing rocks)
What are chemical and biochemical sedimentary rocks? How are they classified? What’s an example related to Manitoba’s economy?
They form when minerals are extracted from solution by inorganic chemical processes or by organisms (biochemical)
> crystalline (mostly chemical) or clastic (mostly biochemical) texture
> classified based on composition and the minerals they contain
> ex. limestone (chemical or types of biochemical like chalk)
*ex. Gypsum : important for manitoba’s economy because it makes drywall
What is clastic texture?
Characteristic of sedimentary rocks that are made up of broken fragments, or clasts, of pre-existing rocks
What are Metamorphic Rocks? What are the types of metamorphic changes?
Igneous and sedimentary rocks that are altered by heat and pressure
Types of metamorphic changes:
- new minerals are formed > compositional
- minerals are aligned > textural
- combination of compositional and textural > foliated
What causes metamorphism?
- heat
- pressure : lithostatic pressure or differential pressure
- fluid activity
What are the two main types of metamorphism? others?
Regional:
- large areas, large movements of rocks deep under the surface
- mountain building type environment
- most metamorphic rocks result from this
Contact:
- mostly derived by high heat
- ex. limestone transformed to marble due to high heat from nearby magma intrusion
others: shock, dynamic, burial, hydrothermal
What is foliated texture?
When rocks are subjected to differential pressure, the mineral grains are typically arranged in a parallel fashion, producing a foliated texture
> elongated minerals arranged in a parallel fashion as a result of either…
shear stress: pressure going parallel against the grains in two different directions ^
direct pressure: pressure applied to two sides inwards –> <–
> Some rocks don’t develop any obvious orientation of their minerals - have a mosaic of roughly equidimensional minerals and have a nonfoliated texture
What are some examples of foliated metamorphic rocks? And nonfoliated metamorphic rocks?
foliated: slate (typically from mudrocks, very fine grain sedimentary rocks), gneiss, schist, migamite
nonfoliated: marble (comes from limestone) and quartzite (comes from sandstone)
How are metamorphic rocks classified? Different types?
Primarily classified based on texture and specifically whether they are foliated (formed in an environment with direct pressure or shear stress) or nonfoliated (no direct pressure or near the surface with little pressure)
ferromagnesian silicates are _____ coloured and non ferromagnesian silicates are ______ coloured
darker
lighter
What does the rock cycle show about the 3 major rock groups?
Shows that they are interrelated > any can be derived from either of the other two
