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277 Cards in this Set

  • Front
  • Back
Rocks rich in silica
Silicic
Rocks rich in iron and magnesium
Mafic
Rocks super rich in iron and magnesium
Ultramafic
In between silicic and mafic
Intermediate
Crust contains what type of rock? continental and oceanic..
continental - silicic
oceanic - mafic
Mantle contains what type of rock?
Ultramafic
Outer and Inner core contain what type of elements?
Outer - Liquid Fe and INi
Inner - Solid Fe and Ni
Igneous rocks formed by:
solidification of a melt
Magma
melt in the interior of the Earth - the second it reaches the surface it's not magma anymore
Lava
melt at the surface of the Earth
Between what temperatures will rocks melt under surface conditions
Between 650 and 1100
How how is your household oven
500 degrees Celsius
The inner core reaches what temperature?
4300C
The Lithospheric mantle ranges from what temperatures?
500-12800
The crust ranges from what temperatures?
0-500C
How do rocks of mantle remain solid?
they are under extremely high pressure
Heat-transfer melting
By increasing the temperature you will reach the point at which rocks melt even under high pressure
Decompression melting
By reducing pressure you decrease the melting point of the rocks
Flux Melting
Adding volatile elements like water or co2 decreases the melting point of rocks
Where does heat-transfer melting take place
Up through the lithospheric mantle where magma melts the surrounding rock
Where does flux melting occur?
Water and co2 get squeezed out of subducting slab at subduction zones
Intrusive Igneous rocks
solidified inside the Earth from a magma - coarse grained
Extrusive igneous rocks
solidified on the surface of the Earth from a lava, fine-grained
Why do igneous rocks have different compositions?
because they solidified from melts with different compositions
Granite composition
66-76% silica, silicic
Diorite composition
52-66% silica, intermediate
Gabbro composition
45-52% silica, mafic
Peridotite (mantle rocks) composition
38-45% silica, ultramafic
Three ways of getting magma of different compositions?
Partial melting, fractional crystallization, Magma contamination
Partial Melting
only some minerals add to the composition of the new melt because not all minerals melt at the same time
Fractional crystallization
in magma chambers, heavy magma sinks to the bottom - not all minerals crystallize at the same time so only some actually stay in the rising magma and make it to their destination
Magma composition
As magma travels up to surface, light felsic crustal rocks break off into the flow of magma and melt, enriching upstream flow with silica
Dike
rock feature that cuts across layers
Sill
Pushes between layers of rock
Laccolith
Blister-like sill that pushes up overlying layers
Pluton
Also called batholiths, usually refer to a distinctive mass of igneous rock
Ability of lava to flow depends on its
viscosity
the more viscous a substance is, the faster/slower it flows
slower
water has high/low viscosity
low
honey has high/low viscosity
high
The more silica the lava contains, the greater/lower its viscosity
greater
Viscosity of lava depends on its content of
silica
What does a highly viscous lava flow look like?
dome-like shape, travels little distance
What does an intermediately viscous flow look like?
thick flow, travels some distance
What does a fluid lava flow look like?
thin flows, travels great distances
What are the two types of eruptions?
Explosive (gray) eruptions, effusive (red) eruptions
What level of viscosity results in an explosive (gray) eruption?
HIGH viscosity
Why does viscous lava explode more?
Gas escapes slower from a viscous lava so more gets trapped
What happens to bubbles of gas as they move up to lower pressure
They expand and become HUGE
Part of the volcano where the the main lava pipe comes out
Summit vent
part of the volcano where an auxillary flow of magma comes
flank vent
underground cavity of magma under the volcano
magma chamber
Silica: low
viscosity: low
Gas content: low
Type of flow: thin
shield volcanoes
Shield volcano type of eruption:
primarily effusive lava flows
Silica: Intermediate
Viscosity: Intermediate
Gas content: Intermediate
Type of flow: Thin
Cinder cone volcano
Cinder cone volcano type of eruption
very explosive at vent, effusive lava flows
Silica: high
Viscosity: high
Gas content: high
Type of flow: thick, dome
Stratovolcano
Stratovolcano type of eruption
Primarily explosive pyroclastic eruptions
What do stratovolcanoes look like?
Very large cone-shaped mountain
Granite, diorite gabbro - intrusive or extrusive?
Intrusive
Name three extrusive rocks
Rhyolite, Andesite, Basalt
How many plate interact at the Cascades?
three
What type of volcanoes are the Cascades?
Stratovolcanoes (big mountains)
What are the layers of a stratovolcano
alternating eruptions of explosive pyroclastic material and effusive lava flows
Which type of volcano is prone to landsliding?
Stratovolcano
What does volcanic ash consist of
microscopic particles of rock shards and glass
What is a lahar
fast-moving mudflow-likes slurry of ash, debris, and water
Biggest hazards of stratovolcanoes
Ash fall, pyroclastic flows, lahars, and landslides
How far are the Hawaiian Islands from the nearest plate boundary?
3520 km
What's going on with Hawaii?
Hot spot - part of a volcanic mountain chain that is largely underwater
What is a hot spot?
a location at the base of the lithosphere, at the tope of a mantle plume, where temperatures can cause melting
What is a hot spot track or train?
chain of now-dead volcanoes transported off the hot spot by the movement a tectonic lithospheric plate
What is a hot-spot volcano?
not caused by movement of a plate boundary - malting of a mantle plume
What is the Hawaiian Island Seamount Chain?
Undersea mountain range where Hawaii is - starts in North/South direction then turns more laterally
How did the Seamounts form?
Stationary hot spot - Pacific plate was moving north until 43 million years ago - changed to a NW direction 40 million years ago
Which plate are the Hawaiian islands smack in the middle of?
The Pacific Plate
How many volcanic centers are there in Hawaii? active-dormant
3 active, 14 dormant
How many Hawaiian islands are there?
8
What are the active volcanoes in Hawaii?
Mauna Loa, Loihi, and Kilauea
How big are hotspots generally?
hundreds of kilometers wide
When did Mauna Loa last erupt?
1984
When did Loihi last erupt?
1996
Which volcano in Hawaii is still producing lava flows?
Kilauea
Which of the Hawaiian volcanoes is the youngest and is still underwater?
Loihi
What is the crater associated with the Kilauea volcano?
Pu'u 'O'o Crater
When did Kilauea last erupt?
1982
How high is Loihi as measured from the sea floor?
3000 meters
When was Loihi first identified as a volcano?
1970
When was the first eruption of Loihi?
1996
What are pillow basalts?
Blob-like shaped pieces of lava formed under water
What are the major hazards of red volcanoes?
Lava bombs, lava flows - pahoehoe and Aa
Explain lava bombs and why they occur
Although lava has lost most of its gas content by the time it reaches the surface, there is still some that causes explosions - lava bombs are bits of lava that cool before hitting the ground
What are Pele's tears?
lava that cools so fast that they turn into black glass
What trails behind lava bombs?
Hair thin pieces of cooled lava
How far can lava bombs fly?
Hundreds of meters from the vent
What are the two types of lava flows?
Pahoehoe and Aa
What are pahoehoe flows?
Drag of fluid inside lava flow pulls the surface into ropy ridges
What are Aa flows?
rubbly flow with jumbled angular pieces - too thick to turn to ropes - distal edge of lava flow
Where did the name Aa come from (myth)?
people walking over them and saying "ah ah ah"
Explain catastrophism
Basically the idea that the processes that laid down rocks were biblical floods in some capacity
"processes that laid down rocks are no longer with us"
Catastrophism
What did most naturalists think about Noah's flood by the late 1700s?
Most naturalists didn't take the story literally
Who was the famous friend of James Hutton?
Adam Smith
What theory did James Hutton propose?
Uniformitarianism
Define uniformitarianism
The slow, gradual processes that are shaping the geology of our planet today are sufficient to explain the geology of the past
When did James Hutton live?
1726-1797
Who was the strict-uniformitarianism that did not believe in any catastrophes?
Charles Lyell (1797-1875)
"cumulative slow change produced by natural processes operating at RELATIVELY CONSTANT RATES" - who would have said this?
Charles Lyell
True/false - Hutton argued that slow, gradual processes are the only things shaping geology
false - he thought it was a combination
What did Hutton think were a result of catastrophe?
mountains
What first led Hutton to the idea of gradual change?
beach erosion
Neocatastrophism?
sudden, high magnitude events do happen - but gradual processes are as important - laws of the universe do not change
How is clastic sedimentary rock formed?
mineral material that precipitated between the grains and "glued"/cemented them together
How is crystalline sedimentary rock formed?
chemicals are transported in solution, then when water evaporates the grains tightly interlock with one another like a jigsaw puzzle
What does cemented texture look like?
layers
What are clastic sedimentary rocks?
Cemented together fragments of pre-existing rocks
What are chemical sedimentary rocks and what kind of texture do they have?
Precipitation of crystals out of a solution - interlocking
What are the two types of sedimentary rock textures?
Cemented, interlocking
What are biogenic sedimentary rocks?
clasts/grains consisting of skeletal material - underwater from bones of shellfish
Why are grains from a desert environment frosted?
Because the wind blows them around so they scratch each other a lot
Where is the world's biggest desert?
Antarctica
Sand grains transported by water are ?
highly polished
Discuss well-sorted vs. poorly sorted grains
wind has a narrow size range that can be carried, unlike water. Most sediments in the desert, carried by wind, are "well-sorted" because there is a narrow range of size that wind can transport
What is the stoss side
The side facing the wind - the side the wind blows up
What is the lee side?
The side on which grains are dumped - faces the direction in the dune will move
What are cross-beds?
Areas where you see tons of crossing sedimentary layers because each dune has layers in itself and then you could have hundreds of moving layers in each desert
Where is there a big cross-bed and why is it there?
Zion National Park, UT - deposited when North America was at the the heart of Pagaea in a huge desert rainshadow
How tall were some of the dunes in the desert in N. America when Pangaea existed?
kilometers high
Why do you find very few terrestrial fossils in desert environments?
Things get eaten very quickly, little life to begin with
What do you find in desert rocks instead of fossils?
Tracks
How do tracks get fossilized?
Dew in the morning causes tracks to glue together and get baked in the sun - quickly covered with sand from elsewhere and preserved that way
What are evaporites?
sedimentary rocks or minerals that form by evaporation of a solution enriched in minerals
What do evaporites look like in the rock record?
spaces left behind by evaporite minerals that dissolved after the sediment had hardened
How do evaporites form?
puddles form and create a solution - water evaporates and gypsum crystals form - get buried and can become lithified
What do evaporites tell you?
There must have been a very hot environment
What do you see in a core sample from a lake?
Alternating layers of light and dark laminations formed by the very fine-grained sediments that make it to the center of the lake
Why are there alternating colors in a lake core sample?
During summer, lake gets a lot of fine/light sediment - during fall/winter, lake gets a huge carbon influx as stuff dies
In a lake core sample, what do the light and dark layers signify
light - summer, dark - winter
Why are lake environments geologically ephemeral?
they eventually fill up with sediment
What is a varve?
A lamination
How can you determine the age of a lake
count the number of laminations/varves like tree rings
What are metamorphic rocks?
What rocks permanently turn into when they are altered by heat and pressure
What is physical deformation?
Normal physical stress - compression and extension
What is change in physical deformation of rocks?
the physical shape of the grains
Explain shear stress
Rock is pushed in 2 opposite directions and everything is skewed - on an atomic scale you create shear planes
What are chemical changes of rocks?
Run superhot fluids through the grains of a rock - grains fuse and recrystallize, usually into bigger grain-size crystals
what is a solid-state phase change
Same exact elements but different arrangement - results in different properties
How does the crystal structure of atoms in minerals change during a solid-state phase change?
Instantaneously
Polymorphs
Crystals of the same mineral but with different atomic structures
With increasing pressure, alpha-quartz turns to...
beta-quartz, then into coesite
What is neocrystallization?
At the right pressures/temperatures, completely new minerals can form - chemical reactions (weathering) digest the minerals of the original rock which yields new minerals
What is an example of neocrystallization?
Garnet - combination of quartz, iron oxide, and micas
Pressure solution metamorphism
At low temp/pressure minerals dissolve at pressure surfaces between grains, causing grains to fuse together
What are the four processes of metamorphic change?
Recrystallization, phase change, neocrystallization, pressure solution
Foliated metamorphic rocks
Flattened grains, expanded horizaontally - all grains turned into pancakes - is a type of grain organization
What type of rock is slate?
Foliated metamorphic
As you increase pressure, what does mudstone turn into?
Mudstone -> slate -> phyllite -> schisst -> Gneiss
How do you know if a metamorphic rock is foliated?
They exhibit some form of mineral alignment due to shear or normal stress
Formation of Marble
Recrystallization of limestone occurs and the grains/fossils are destroyed - marble retains original composition - no mineral foliation
Formation of quartzite
Quartz-rich sandstone (SiO2) - recystallization + pressure solution = grains fuse into interlocking texture
What does quartzite look like?
giant lumps of quartz with a mottled surface texture when broken
Why doesn't quartzite take on foliation?
resistance of quartz grains to deformation, and lack of elements available inside the protolith for neocrystallization to form micas
Hornfels
non-foliated metamorphic rocks that are the result of heating and little to no pressure
How do hornfels usually form?
As the result of "baking" by an igneous intrusion into shallow crustal rocks (less than 3 km deep)
What are the common nonfoliated metamorphic rocks?
Marble, quartzite, hornfels
Where do neocrystalline grains grow in foliated metamorphic rocks?
Perpendicular to stress
What are reasons for metamorphic rocks not taking on foliation?
Minerals that resist deformation or recrystallize w/o preferred orientation, rocks experiencing too little stress, protoliths lacking minerals that could provide elements for neocrystallization of aligned minerals
Formation of Marble
Recrystallization of limestone occurs and the grains/fossils are destroyed - marble retains original composition - no mineral foliation
Formation of quartzite
Quartz-rich sandstone (SiO2) - recystallization + pressure solution = grains fuse into interlocking texture
Difference between faults and folds?
Faults - brittle deformation
Folds - ductile deformation
What does quartzite look like?
giant lumps of quartz with a mottled surface texture when broken
Why doesn't quartzite take on foliation?
resistance of quartz grains to deformation, and lack of elements available inside the protolith for neocrystallization to form micas
Hornfels
non-foliated metamorphic rocks that are the result of heating and little to no pressure
How do hornfels usually form?
As the result of "baking" by an igneous intrusion into shallow crustal rocks (less than 3 km deep)
What are the common nonfoliated metamorphic rocks?
Marble, quartzite, hornfels
Where do neocrystalline grains grow in foliated metamorphic rocks?
Perpendicular to stress
What are reasons for metamorphic rocks not taking on foliation?
Minerals that resist deformation or recrystallize w/o preferred orientation, rocks experiencing too little stress, protoliths lacking minerals that could provide elements for neocrystallization of aligned minerals
Difference between faults and folds?
Faults - brittle deformation
Folds - ductile deformation
What types of folds form from compressional stress?
Synclines, Anticlines, and Monoclines
Which type of fold is like a Smiley face?
Syncline
Which type of fold is like a mountain
Anticline
Which type of fold is just like a wavy line
Monocline
What is an angular fold with straight things
Chevron folds (syncline or anticline)
What type of structure is the lady's cave?
Chevron fold
What is the part of a fault that is uncovered by the land slipping away? (diagonal)
Fault plane
What do you call the distance the land fell in a fault?
Fault scarp
What is the edge lining the fault plane called?
Fault trace
Which "wall" is the one that stays still?
Footwall
Which "wall" is the one that is fattest on top?
Hanging wall
In a normal fault, in which directions do the "walls" move?
Hanging wall moves down, footwall moves up
In a reverse fault, in which directions do the "walls" move?
Hanging wall moves up, footwall moves down
In a transform fault, in which directions do the "walls" move
Sideways (footwall towards you, hanging wall away?)
What faults are associated with the term dip-slip?
Reverse fault, normal fault
What fault is associated with the term strike-slip?
Transform fault
Type of stress associated with reverse fault
Compressional
Type of stress associated with normal fault
Extensional stress
Type of stress associated with transform fault
Shear stress
Thrust fault
Gently dipping reverse fault - layer of older rock laid on top of older rock
Intraplate fault
Small fracture in interior of plate - pressure can build up and cause earthquakes
What proportion of earthquakes occur along plate boundaries
about 99%
Earthquakes along mid-ocean ridges
there are large fracture zones along the mid-ocean ridge - you can get slippage/movement on transform faults that cas
How do earthquakes happen?
Faulting causes pressure buildup and when it fails, you get seismic waves
Analogy for surface waves
Surface of water when you drop a pebble in
Analogy for body waves
Energy that propagates through the interior of the water when you drop a pebble in- can't see
Besides tectonic earthquakes, what kinds are there?
Volcanic, collapse (landslide or cave collapse), impact explosion (nuclear detonations, fuel plant explosions),
What are the most common types of natural quakes?
Tectonic and volcanic
What is the point of the earthquake where the disturbance occurs (underground)?
Focus
What is the point on the surface directly above the focus?
Epicenter
How do shear waves move?
Particles move up/down or left/right
How do compressional waves move?
particles move back and forth parallel to the direction of wave motion
What are the four types of waves?
Compressional body waves (p-waves), shear body waves (S-waves), Shear surface wave type I (r-wave), Shear surface wave type II (L-wave)
What is the primary, fastest-moving type of seismic wave?
P-waves (compressional body)
What is the secondary wave?
S-wave (shear body)
describe a Rayleigh wave
circular surface wave - magnitude decreases with depth
Describe a Love wave
Side to side surface wave - decreases with depth
What are the major hazards during an earthquake?
Ground shaking, landslides, and liquefaction
What are the major hazards after an earthquake?
Fire, disease
What is pancaking of buildings?
floors of a building collapse on each other because the columns in between aren't strong enough to withstand shaking
Ground shaking is primarily caused by which type of waves?
Shear waves
What type of ground surface expresses seismic waves the strongest?
Water-logged sediment
Where is one of the safest places to be during an earthquake?
a mine
What type of column is made now that can withstand earthquake shaking
Concrete inside a steel jacket - even if the concrete crumbles it is still contained
What U.S. areas are in major danger of landslides from earthquakes?
Southern CA to L.A. with expensive real estate, place where the Great Alaska Christmas earthquake happened
What is liquefaction
water-logged soils turn to slurry when shaken by earthquakes
What are sand blows
Cracks or holes in the ground open up when liquefaction occurs, and water gushes out above where a slurry has been created/shaken up
What is the big problem with fires after earthquakes/
Since there is so much debris everywhere, it's very hard to get to fires to put them out - lots of times hydrant pipes have been broken also
Two examples of huge fires after earthquakes
1906 San Francisco - Kobe, Japan
What has Kobe, Japan done to counter dangers of fires with earthquakes
Have built underground steel tubs filled with water every two blocks
Examples of really bad disease outbreaks after earthquakes
Haiti, Pakistan, Indonesia
What is the recorDER of earthquakes
seismometer
What is the recordING of earthquakes?
Seismogram
What is the I-XII intensity scale and who invented it?
Giuseppe Mercalli - 12 categories to describe the damage done by an earthquake
What does the Mercalli Intensity Scale range from
I-XII
problems with Mercalli scale
buildings respond differently, varies depending on distance from epicenter, relies on eyewitness reports
Why is there minimal shaking in Appalachian mountains during an earthquake?
It is underlain by hard metamorphic rock
how does the Richter scale work?
Measures the relative amount of energy released by determining the amplitude of the largest ground motion
Biggest problem with Richter scale
Loses resolution for quakes >7.0 (also only uses one source for data)
What is the earthquake scale we use today?
Moment Magnitude Scale
An increase of one unit of magnitude on the Richter scale equals:
33 times more energy
What things does the Moment Magnitude Scale include in its calculation?
Length of the fault rupture, area of rupture surface, and shear strengths of rocks
Igneous rock formation
formed as solidifications of a melt
Do silicic and felsic rocks have any Mg or Fe in them?
yes, but proportionately more silica
How does rock composition relate to the temperature required to melt it?
Generally, more Fe and Mg require higher temperature to melt
Why don't rocks in the mantle melt?
Because they are at such high pressures
Decompression melting
Parcel from mantle moves fast enough up to the lithospheric mantle, pressure change causes melting
heat transfer melting
melt flows into cracks and burns its way through the lithosphereic mantle
What percentage of parcels from the mantle never make it to the surface?
90% - because they usually go cold before reaching crust
Intrusive igneous rocks
solidfy inside the Earth - have time to arrange themselves into intricate crystal patterns
Relationship between grain size and cooling time?
Rapid cooling - fine grained, slow cooling - coarse grained
Generally, of what grain size are volcanic rocks?
Fine-grained
How fast do convection cells of magma move?
one rotation takes hundreds of thousands of years
Partial melting
not everything melts at the same temperature - silica minerals melt more easily
How does magma chamber differentiation happen?
Mafic minerals crystallize before silicic minerals - so magma becomes more silicic and the crystallizes mafic minerals sink to the bottom of the less dense magma chamber
Magma Assimilation/Contamination
Silica crust breaks off and melts into the magma flow, adding lots of silica to the magma
Dike intrusion
sheet of igneous rock that cuts discordantly across rock structures/formations
Sill
too much magma in a dike expands laterally between layers
Laccolith
sill fills more and warps the layers up above
Pluton
irregular blob of magma that never reaches surface
Category of "plutons" includes:
batholiths, dikes, sills, laccoliths, other igneous bodies
Most fluid type of lava has what kind of composition?
Most magnesium and iron
What type of lava tends to lead to really explosive eruptions?
Viscous - high in silica
What is an effusive eruption like and where do they occur?
fluid - typical of Hawaii - hot spots
Why does viscous lava make bigger explosions?
Giant bubbles of gas form and can't escape - then they dramatically expand as pressure decreases
Flank vents - what are they, when do they happen?
kind of like an escape route for lava - happen when main vent is plugged up with old magma
Where are there shield volcanoes in the U.S.?
Hawaii
Where are there stratovolcanoes in the U.S.?
the Cascades (WA, OR)
Where are there cinder cone volcanoes in the U.S.?
In the Southwest but they are largely inactive
What is the number one hazard associated with stratovolcanoes?
Big chunks break off since stratified layers cause the mountain to be unstable
What is the last volcano to have erupted before St. Helens?
Lassen
What type of plate boundary are the Cascades near?
Subduction zone
When did Mt. St. Helens erupt?
1980
What was the level of the earthquake produced by the St. Helens eruption/
3.0
How far did the landslide after Mt. St. Helens travel?
50 miles
How fast do pyroclastic flows travel?
150-180 mph
Worst pyroclastic flow
1902 - St. Pierre on Island Martinique - killed everyone but 2
Lahar flows
result of stratovolcano erupting during higher rainfall - steaming, boiling mud flow 100s of degrees hot
Most famous Lahar flow
Colombia in the 80's that covered the whole village