exam 2 Flashcards
petrology
the study of rocks
igneous rock
form directly from a magma via freezing/crystallizing; made up of randomly distributed crystals, characterized by shade and texture
bowen’s reaction series
minerals freeze at varying temperatures; quartz melts at 800, olivine and plagioclase melt at 1200, potassium feldspar is in the middle
dark igneous rocks
mafic
light igneous rocks
felsic
phaneritic texture
coarse crystals visible to the naked eye, cool slowly 1-10 mi underground, plutonic
aphanitic texture
fine crystals that require magnification, cool rapidly on the surface, volcanic
granite
felsic phaneritic igneous rock
diorite
intermediate phaneritic igneous rock
gabbro
mafic phaneritic igneous rock
rhyolite
felsic aphanitic igneous rock
andasite
intermediate aphanitic igneous rock
basalt
mafic aphanitic igneous rock
obsidian and pumice
glassy igneous rocks
magma
liquid rock located 1-10 miles underground
batholith
frozen body of igneous rock deep underground that contain rare elements, become exposed by extensive uplift and erosion
sills
branches of batholiths in the host rock that freeze horizontally
dikes
branches of batholiths in the host rock that freeze vertically
igneous intrusions
more resistant to weathering than the host rock ex: stone mountain in Atlanta
active volcanos
any eruption during human history
dormant volcanos
sleeping/inactive but have the potential to erupt, no human has seen it erupt
extinct volcanos
no longer has the potential to erupt
effusive eruptions
lava flow, quiet and controlled eruptions from mafic volcanos; caused because they contain iron rich minerals which melt at high temps (1000-1200) so all minerals are melted form shield volcanos
shield volcanos
10x wider than they are tall, primarily made of basalt, have effusive eruptions
explosive eruptions
violent, producing mostly ash and limited lava from felsic volcanos; minerals melt at low temperatures (800-1000), not all minerals melt at once causing blockages that build up pressure, form composite volcanos
composite volcanos
steep, made up of built up ash and primarily rhyolite, smaller because they destroy themselves, have explosive eruptions
pyroclastic material
ash
caldera
hole in a volcano
phreatic eruptions
very big explosive eruptions surrounded by water, powered by steam when water enters the magma chamber, krakatoa and tambora
sedimentary rocks
made up of cemented debris, stratified, bedded, layered, give earth’s history form at 50-250 degrees
4 step process of sedimentary rock formation
weathering, erosion, deposition, lithification
weathering
atmosphere attacks rocks causing decay
mechanical weathering
physical, decreases size and increases surface area, ex: freeze thaw
chemical weathering
reactions that change the mineral composition to a more stable form from atmospheric chemicals
oxidation - mafic minerals oxidize to rust
hydrolysis - feldspar hydrates to clay
carbonation - CO2 forms carbonic acid which dissolves carbonate minerals
erosion and deposition
dependent on size of clasts and speed of movement
sand
clasts 2-0.05mm
silt
clasts 0.05-0.002mm
clay
clasts <0.002mm
fluvial processes
flowing water is a vehicle to transport sediment and dissolved minerals
eolian processes
flowing wind moves small clasts such as clay globally, silt shorter distances, and sand very short distances forming dunes
loess
wind blown silt deposits
lag gravel
clasts left behind because they are too big to move by wind
total fluvial transport
bedload (movement on the bottom that moves by saltation) + suspended load + dissolved load
glacial processes
flowing ice in polar or alpine regions, or Pleistocene climates
lithification
compaction and cementation over time by adding weight, quartz, calcite, and iron are common glues, requires 10s of millions of years, generates 50-250 degrees of heat
clastic sedimentary rocks
based on size, form via mechanical weathering, made of sand silt and clay, rough grainy texture
sandstone
grainy texture made of quartz sand clasts, forms in a high energy environment
shale
made of clay clasts, flat shape, fissile, forms in a low energy environment
fissile
breaks into thin sheets
nonclastic sedimentary rocks
biochemical, form via chemical weathering, undissolved precipitates
limestone
nonclastic sedimentary rock, gray, varying thickness, can contain fossils, made up of calcite, fizzes with HCl, forms in shallow marine environments
coal
compacted organic matter, require a tropical climate, forms in swamps of shallow water to prevent decomposition; pressure and heat convert peat to coal over a long period of time
lignite
first stage of coal formation, water is removed from peat
bituminous coal
soft bedded coal found in western PA
anthracite
hard shiny coal found in eastern PA
coquina
nonclastic sedimentary rock made up of broken shells, fizzes with HCl, can compact further into limestone
chalk
white, dull, nonclastic sedimentary rock fizzes with HCl
chert
similar to limestone in appearance, vitreous with conchoidal fractures, used for arrow heads
conglomerate
clastic sedimentary rock formed from water, rounded pieces of rock debris, non uniform
breccia
clastic sedimentary rock formed from earthquakes, angular rock debris, non uniform
siltstone
clastic sedimentary rock, very fine sandstone
metamorphic rocks
changed by heat and pressure cooks rocks creating aligned mineral crystals different from the original form at 250 - 750 degrees
foliation
swirls and bands on metamorphic rocks
methods of metamorphic formation
burial and tectonics both require depth followed by erosion and occur on a large scale, contact metamorphism is smaller scale
burial
under 10’s of km’s of material creates high pressure and increases heat
tectonics
pressure from the sides pushes materials in and up, acts on the roots of mountains
contact metamorphism
as plutons of magma move towards the surface in dikes and sills, they cook the walls of the host rock, 1-10ft below the surface
metamorphosis of shale
compresses to slate (low grade) which compresses to phyllite which compresses to schist which compresses to gneiss (high grade)
slate
harder, darker, and smoother than shale
schist
sparkly due to muscovite mica
phyllite
shiny aligned layers
gneiss
zebra striped in pink or white and black
marble
contact metamorphizes from limestone, still fizzes under HCl
quartzite
contact metamorphizes from quartz sandstone