GEO 109 Unit 2
reverse
fault that: -results from compressional stress -accomodates crustal shortening
hot-spot track
in the Hawaiian Island-Emperor Seamount Chain, this formed as the Pacific Plate moved over the hot spot
seafloor spreading
the process of producing new seafloor between two *diverging* plates
surface (SFD)
waves that we feel; what causes damage
-lava flows (pahoehoe or aa) -gas -pyroclastic materials (ash and bigger pieces) (PLG)
3 categories of materials extruded in a volcanic eruption
bed load, suspended load, dissolved load
3 types of loads carried by streams
-dissolved load: material in solution (-delivered by groundwater -not effected by velocity) -suspended load: material suspended in the water (-clay and silt particles -largest component) -bed load- material moving along the channel bed (-sand, gravel, large boulders -only in motion intermittently -smaller particles move via saltation -largest particles roll or slip)
3 ways streams transport sediment
Richter scale
A scale that rates an earthquake's magnitude based on the size of its seismic waves
Seismology
The study of earthquakes
-on both sides of the mid-ocean ridge
Where would you expect to see alternating bands of rock with different magnetic polarities?
tsunamis
Which hazard generated by earthquakes can be destructive many hundreds of kilometers away from the epicenter?
gravel, sand
Which of the following are part of the bed load? -ions -clay -gravel -sand
d
Which of the following are true of earthquakes a) an earthquake is always preceded by aftershocks b) an earthquake originates at the epicenter c) an earthquake builds up strain in the rock d) an earthquake originates at the focus
continental drift
a theory that was *replaced* by the plate tectonics theory, that the continents are rafted about
convection
a type of heat transfer that involves the actual movement of a substance
The subduction of oceanic crust under oceanic crust
a volcanic island arc is the result of...
a, d (only convergent boundaries do subduction)
The production of magma (magmatism) at divergent boundaries is characterized by which of the following? a) Outpourings of lava/magma originating from the mantle. b) Melting caused by subduction c) Outpourings of lava/magma originating mostly from the continental crust. d) Melting caused by decompression
ductile deformation
change in the size and shape of a rock that occurs at depth
less (convergent plate boundaries)
continental crust is --- dense than asthenosphere
no, transform don't
do all plate boundaries have volcanic activity
-dislodge and lift particles from the channel (-erodes poorly consolidated material quickly -can undercut banks)
flow of water in a stream can...
transform plate boundaries (-transform faults -connect spreading centers and offset oceanic ridges -active faults occur between offset ridge segments -few transform faults cut through continental crust but San Andreas Fault and Alpine Fault are exceptions)
form when two plates slide *horizontally* past one another
brittle deformation
fracturing of rocks that occurs at or near the surface; leads to faults
moment magnitude
measures total energy released based on amount of slide, area of rupture, and strength of faulted rock
magma
molten rock containing crystals and dissolved gas; source material for volcanic eruptions
weather (Snowmelt, heavy rains over large regions -Flash floods (-Limited geographic extent -Influenced by rainfall intensity, surface conditions, and topography) -Failure of dams or artificial levees)
most floods occur bc of ---
turbulent
most stream flow is ----; meaning water moves erratically in a swirling motion and lifts sediment from streambed
Continental volcanic arc
mountains formed in part by volcanic activity caused by the subduction of oceanic lithosphere beneath a continent
mechanism (*Wegener proposed* that *tidal forces* moved continents and that sturdy continents broke through thin oceanic crust)
objections of Wegner's hypothesis were based on lack of ----- for continental drift
convection
occurs as hot, less dense material rises and surface material cools and sinks
elastic rebound (earthquakes)
the sudden return of elastically deformed rock to its undeformed shape
Curie point
the temperature above which a material loses its magnetization
Plate Tectonic Theory
the theory that the lithosphere is broken up into large plates that move and then rejoin; considered the unifying theory of geology
-some travel along Earth's surface like rolling ocean waves -others move Earth materials from side to side (most damaging type of ground motion)
the two types of surface waves; what's the most damaging type
discharge (streamflow)
the volume of water flowing past a certain point in a given unit of time
-lithosphere is broken into irregular plates (plates move as rigid units relative to other plates) -Interactions between plates at plate boundaries (divergent boundaries, convergent boundaries, and transform plate boundaries)
theory of plate tectonics
hydrologic cycle
water moving between the ocean, atmosphere, and land
-connect spreading centers and offset oceanic ridges
what *transform* plate boundaries do
-stream channels that are composed of loosely consolidated sediment -its shape is controlled by avg sediment size (can change) -two common types: meandering channels and braided channels
what are alluvial channels
-floods occur when stream *discharge exceeds channel* capacity -most floods occur bc of weather (-snowmelt, heavy rains over large regions -Flash floods: limited geographic extent; influenced by rainfall intensity, surface conditions, and topography -failure of dams or artificial levees)
what causes floods
divergent, convergent, transform
three types of plate boundaries
magnetism
(a) pieces of evidence that supports the plate tectonic theory: The *stripe patterns* of high- and low-intensity ---are mirror images on both sides of an *oceanic ridge*
deformation (two types are brittle deformation and ductile deformation)
-*all* changes in shape, position, or orientation of a rock mass -bending and breaking occurs when *stress exceeds* strength
convergent plate boundaries
-*occur when two plates move toward each other* (-convergence rate is equal to seafloor spreading; -characteristics vary depending on subducting crust) -*lithosphere descends into the mantle* (old oceanic crust is about 2% denser than asthenosphere; continental crust is less dense than asthenosphere) -*deep ocean trenches* (long, linerar depressions; result of subduction)
-Gradient (of a river) -Discharge
-*vertical drop* of stream over a specified distance -*volume* of water *flowing past* a certain point in a given unit of time
steeper
--- gradient provides more energy for flow
-iron-rich (basalt erupts above the curie temp, so magnetite grains are nonmagnetic -grains align to magnetic field during cooling -rocks preserve a record of the direction of magnetic poles at the time of formation -> Paleomagnetism or fossil magnetism (the branch of geophysics concerned with the magnetism in rocks that was induced by the earth's magnetic field at the time of their formation))
---- minerals are influenced by magnetic pole
a
----- tend to increase the explosive potential of a magma body beneath a volcano by the greatest amount a) high viscosity and lots of dissolved gas b) high viscosity and very low levels of dissolved gas c) low viscosity and lots of dissolved gas d) low viscosity and very low levels of dissolved gas
-volcanic island arc -continental volcanic arc (*convergent* boundaries)
-A string of volcanoes that form as the result of subduction of one oceanic plate beneath a second oceanic plate -mountains formed in part by volcanic activity caused by the subduction of oceanic lithosphere beneath a continent
-they're displaced up and down (SDUD) -they expand and contract (PEC)
-How are rock within Earth affected as S waves pass? -How do rocks within Earth change as P waves pass?
-you would need to determine if the flood size will change which would change your risk of being inside the flood plain at some point in your life -it's useful bc it gives a good estimate in general for flood area; you can predict the future changes in flood size/behavior when possibly adding development/infrastructure in that area
-What info do you need to know if you're about to buy a house that's located adjacent to, but just outside the 100-yr flood plain? -What's the usefulness of the 100-yr flood as a legal designation for these two streams? Remember, this designation determines whether you can build a structure, and your flood insurance rates
magnitude (-measured by Richter scale -moment magnitude measures total energy released based on amount of slide, area of rupture, and strength of faulted rock)
-a *quantitative* measure of energy released in an earthquake
-divide -watershed -trunk stream
-a boundary, usually a hill or mountain, where water will flow in opposite directions on either side -an area in which all water falling in it flows out through one location -The primary river flowing out of a drainage basin
mantle plume
-a cylinder of upwelling hot rock that's beneath Hawaii
rift valley
-a deep canyon along the crest of a ridge resulting from tensional forces -A deep valley that forms where two plates move apart
-floodplain -natural levee -tributary
-a flat surface next to a river channel -a ridge of flood deposits next to a river channel -a river that feeds into another river
hydrosphere (96.5% of hydrosphere is the global ocean; 1.76% is ice sheets and glaciers; about 2% is lakes, streams, groundwater and atmosphere)
-all of the reservoirs where water is held (oceans, glaciers, rivers, lakes, soils, living tissues)
one block of rock slipping past another along a fault (most faults are locked until a sudden slip -Seismic waves radiate out from the *focus* (hypocenter), *where slips begins* -Earth's surface directly above the focus is the epicenter)
-an Earthquake is caused by the sudden movement of ---
fixed (continental drift was suggested but not agreeable)
-before 1960, geologists saw the positions of ocean basins and continents as ----
-divergent -convergent
-boundary that involves upwelling of hot material from mantle creates new seafloor -boundary where oceanic lithosphere descends and is reabsorbed into mantle
transform plate boundaries
-boundary where two plates slide past each other
shield volcanoes (Mauna Loa is largest shield volcano on Earth- 9 km high; low angle slopes)
-broad domes structures built by accumulation of basaltic lava -most begin as seamounts -mostly associated w/ oceanic hotspots
convergent
-characteristics of ------ plate boundaries vary depending on type of crust being *subducted*: -oceanic + continental -oceanic + oceanic -continental + continental
buoyant
-continental crust is ----- (-neither plate subducts during continent-continent collosions; folding and deformation of rocks; mountain building)
Circum-Pacific Belt
-convergent boundaries that experience 95% of earthquakes
-sediment age increases w/ distance from *ridge* -sediment is thicker w/ increased distance from the *ridge* -oldest seafloor is 180 million years old
-evidence of Plate Tectonics Model in modern day (from Deep Sea Drilling Project)
-magnetic field reverses polarity during a magnetic reversal (-rocks w/ same magnetic field as today have *normal polarity* -rocks w/ opposite magnetism have *reverse polarity*) -polarity of lava flows w/ radiometric ages was used to generate a *magnetic time scale* -Vince and Matthews (1963) suggested stripes of normal and reverse polarity are evidence of seafloor spreading
-explain how magnetic *fields* support Plate Tectonics Model
-today North and South magnetic poles align approximately w/ geographic North and South poles (Iron-rich minerals influenced by magnetic pole) (as time goes on: normal polarity -> reverse polarity-> normal polarity -see 2/13 PPT slide 18)
-explain how magnetic *poles* support Plate Tectonics Model
normal faults (fault-block mountains are associated w/ large normal faults)
-fault where the hanging wall moves *down* relative to footwall -accomodate extension of crust
Lahars
-fluid mudflows; water-saturated pyroclastic materials move down steep volcanic slopes
-pyroclastic flows
-hot volcanic gas infused in incandescent ash and lava fragments -gravity driven- can move up to 100 km/hr -low-density cloud of hot gases and fine ash on top of layer of vesicular pyroclastic material -caused by collapse of eruption columns
Earth's interior created by its earlier history
-iron and nickel melted and sank to the center to produce iron-rich core -Buoyant rock rose to the surface and formed crust rich in O, Si, and Al -chemical segregation led to iron-rich core, primitve crust and mantle
intensity (-*qualitative*; used for historical records -Modified Mercalli Intensity Scale)
-measures the amount of ground shaking based on property damage
destructive earthquake
-occurs bc tectonic motions builds up stress (-friction keeps the fault from slipping -slipping initiates when stress overcomes friction -*elastic rebound* causes deformed rock to spring back to undeformed position)
continental rifting (divergent plate boundaries)
-occurs when divergent boundaries develop within a continent (-tensional forces stretch and thin the lithosphere -brittle crust breaks into large blocks -eventually become ocean basins)
explosive volcanic eruptions
-pressure decreases as magma rises (dissolved gas forms expanding bubbles) -viscous magma expels fragmented lava and gas (buoyant plumes of material (eruption columns)) -rapid ejection of magma (-reduces pressure in magma chamber -causes further expansion and erruption)
Subduction
-process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary -one plate going under another plate
surface waves; body waves
-seismic waves that travel in rock layers just below Earth's surface -seismic waves that travel Earth's interior
meandering (meanders = name for sweeping bends)
-stream channel that has sweeping bends -high suspended load -deep, smooth channels -most erosion occurs on the outside of the meander, or the cut bank, where velocity is highest -sediment is deposited along the inside of the meander where turbulence and velocity are low, forming point bars -[ ] migrate laterally and downstream
-Lithosphere -asthenosphere (moves independently from lithosphere)
-the crust and uppermost (coolest) mantle -the hotter, weaker mantle below the lithosphere; rocks are nearly melted at this temp and pressure; respond to forces by flowing
Liquefaction
-the process by which an earthquake's violent movement suddenly turns loose soil into liquid mud -occurs when wet soil acts more like a liquid during an earthquake
seafloor spreading (divergent plate boundaries)
-the process by which new seafloor is created along the ocean ridge system -elevated seafloor w/ high heat flow and volcanism -longest topographic feature on Earth's surface (rift valley)
orogenesis (subduction of oceanic lithosphere is the driving force)
-the set of processes that forms a mountain belt; mountain building -where older mountain chains are eroded and less topographically prominent
earthquake
-the sudden movement of one block of rock slipping past another along a fault (most faults are locked until a sudden slip) -Seismic waves radiate out from the focus (hypocenter) where slip begins
gradient (steeper gradient provides more energy for flow) (streamflow)
-the vertical drop over a specified distance
asthenosphere (weak layer; rocks near their melting temp)
-this is where rocks are nearly melted at this temp and pressure -responds to forces by *flowing* -moves independently from lithosphere
divergent boundaries (upwelling = a rising of seawater, magma,, or other liquid)
-two plates move apart; upwelling of hot material from mantle creates new seafloor -places where plates are pulling apart
convergent boundaries
-two plates move together; oceanic lithosphere descends and is reabsorbed into mantle -places where tectonic plates are coming together
Primary or P waves
-type of body wave that pushes/pulls rocks in direction that wave is travelling -temporarily change volume of material -travel through solids, liquids, and gasses
Secondary or S waves
-type of body wave that shakes particles at right angles to direction that wave is traveling -change shape of material -don't travel through liquids or gases
brittle deformation (-common *at/near surface*)
-type of deformation that results in fractures and faults -where is this usually found
ductile deformation
-type of deformation that's solid-state flow at great *depths* -produces a change in the size and shape of a rock -some chemical bonds break and new ones form
-strike-slip fault (ex: San Andreas)
-type of fault that exhibits horizontal displacement
reverse faults (structures formed by brittle deformation)
-type of fault where hanging wall moves *up* relative to footwall -result from *compressional stress* -accomodate crustal shortening
anticlines; synclines (formed by ductile deformation)
-type of fold that's upfolded or arched layers -type of fold associated downfolds or troughs
suspended load
-type of load that involves the fine-grained particles that travel in the water column above the stream bed
infiltration
-water seeping into the ground
folds (formed by ductile deformation) (anticlines; synclines)
-wavelike undulations that form when rocks bend under compression -compressional forces result in shortening and thickening of crust
-volcanism bc of partial melting -generates *volcanic island arcs*-> volcanic cones underlain by oceanic crust)
-what happens when one slab subducts under another at oceanic-oceanic *convergent* boundaries
oceanic-continental convergence (subduction)
-where water from descending oceanic crust triggers *partial melting* of asthenosphere at about 100 km -when the oceanic plate descends into the asthenosphere, water driven from the subducting slab lowers the melting temp of mantle rock sufficiently to generate magma
hot-spot track
A chain of now-dead volcanoes transported off the hot spot by the movement of a lithosphere plate
flood frequency
A statistical assessment that determines the probability of flooding
b
According to the theory of plate tectonics, tectonic plates interact mainly---- a) on the underside of each plate b) along plate boundaries c) near the center of each plate where stress is greatest d) scientists don't know for sure
P wave
After an earthquake happens, which seismic wave arrives at a distant seismographic first
hot spot
An *area* where magma from deep within the mantle melts through the crust above it
b
Complex mountain systems such as the Alps, Appalachians, and Himalayas are generally formed at a: a) divergent boundary b) convergent boundary c) transform boundary d) hotspot
transform fault
Area where the earth's lithospheric plates move in opposite but parallel directions along a fracture (fault) in the lithosphere.
more; oceanic (-Volcanic activity is common at oceanic-continental subduction zones -referring to convergent boundaries)
Because the rocks of oceanic crust are ---- dense than those of continental crust, it is the plate with ---- crust that is subducted below the continent.
-*delta*: When a river reaches a lake or the sea the water slows down and loses the power to carry sediment . The *sediment is dropped at the mouth of the river*. Some rivers drop *so much sediment* that waves and *tides can't carry it all away*. It *builds up in layers forming a delta* -*levees*: The *natural movement of a body of water pushes sediment* to the side, creating a natural levee. The banks of a river are often slightly elevated from the river bed
Discuss formation of deltas and levees
-*Dams decrease flow*; *Levees just keep it* in the stream channel -*More rain or snow* melt mean *more stream flow*
Discuss streamflow and the factors that cause it to change
-Modified Mercalli Intensity scale; qualitative; used for historical records; measures the amount of ground shaking based on property damage -Richter Scale measures magnitude based on the size of its seismic waves; a quantitative measure of energy released in an earthquake; moment magnitude measures total energy released based on amount of slide, area of rupture, and strength of faulted rock
Distinguish between intensity scales and magnitude scales used to describe earthquakes
asthenosphere
Earth's rigid outer layer overlies a zone of weaker and hotter material known as the...
Transpiration (evapotranspiration = The combined amount of evaporation and transpiration)
Evaporation of water from the leaves of a plant
-building dams & levees -channelization
For Green River: suggest possible *human activities* (if any) in the watershed that could have caused the differences *(decrease)* in predicted floods that result from the two sets of data (Note: these two rivers are in different watersheds)
-there could be different surface conditions -different topography/gradient -different amount of water already in the soil
For Mercer Creek AND Green River: Discuss one or more natural causes (if any) in the watershed or in the area that could have caused the differences in predicted floods that result from the two sets of data for these rivers (Note: these two places are only 19 miles apart)
-loss of land bc of increase in development -increase in buildings & structures -loss of infiltration
For Mercer Creek: suggest possible *human activities* (if any) in the watershed that could have caused the differences *(increase)* in predicted floods that result from the two sets of data (Note: these two rivers are in different watersheds)
-yes it could have changed depending on weather conditions, erosion, the loss/gain of water in the river -the flow velocity could also have an effect
For both rives: do you think the size and extent of the 100-yr flood plain has changed? If so, in what way? If not, why not?
-S waves are body waves; vertical surface waves are surface waves. -the amplitude of S waves doesn't decrease with depth, but the amplitude of vertical surface waves does
How are S waves and vertical surface waves different?
A compass points toward the North Pole during normal polarity and to the South Pole during reverse polarity
How are normal polarity and reverse polarity of Earth's magnetic field different?
-reflection, refraction and velocity are used to interpret *composition* and *temp* of *rock* (geophysical models) (RRV)
How are seismic waves used to describe Earth's interior?
rolling, sliding, bouncing
How can pieces of rock in contact with a stream bed move?
Natural levees raise the height of the stream channel, reducing the amount of flooding that will occur on the floodplain
How does the formation of a natural levee impact flooding
rain (in the atmosphere, it condenses into liquid water and falls out of the atmosphere to land as rain)
How does water get from the oceans onto land?
every 100,000 to several million years
How often does the Earth's magnetic field switch polarity?
-reflected; boundaries -refracted; layers -velocity -liquid
How seismic waves are used as the only way to 'see' inside the interior: -waves are ----- at ----- ---- through --- ---- increases w/ depth -*S* waves don't pass through outer core, indicating it's --- (*rrvs*)
-dissolved load -suspended load -bed load
How streams transport sediment -load delivered by groundwater; not affected by velocity -load made of clay and silt particles; largest component of load -load that consists of sand, gravel, large boulders; only in motion intermittently; smaller particles move via saltation; larger particles roll or slip
-neither plate is subducted so there is no volcanism
If both plates have light continental crust, they will collide, moving rock upward into mountain chains, and...
-the denser of the two (-this is typically the older one (like tree rings) -Volcanic activity is common at oceanic-oceanic subduction zones -referring to convergent boundaries)
If the two plates moving toward each other both have oceanic crust, then which one will be subducted
convergent and divergent plate boundaries
In general, at what plate boundaries do both earthquakes *and* volcanic eruptions occur?
A record of Earth's magnetic field is recorded in *oceanic rocks*, which show a clear pattern of changes in Earth's magnetic polarity
In general, what is our best evidence that the orientation of Earth's magnetic field has changed over time?
-on the *overriding* plate, *away* from convergent boundary
In general, where do volcanoes form in subduction zones?
Crust- the thin, outer layer of the earth; made of solid rock, broken into plates (lithosphere) (made of continental and oceanic crust) Mantle-molten rock on which plates float (asthenosphere = upper mantle) Core-Inner layer of the Earth; made of both solid and liquid metals (inner core is dense ball of solid metal; outer core is a layer of molten metal that surrounds the inner core)
List and describe each of earth's major layers. (crust, mantle, core)
1. *c*ontinents fit like puzzle 2.*f*ossils match across continents (-identical fossils found in South America and Africa -opponents of theory explain fossil patterns by rafting, oceanic land bridges, and island stepping stones) 3. *r*ock and geological features match (-2.2 billion-year-old igneous rocks in Brazil and Africa -mountain belts end at coastlines and reappear across oceans) 4. evidence for *g*laciation (ancient climates (plants)) (CFRG)
List and explain the evidence presented by Alfred Wegener to support his continental drift hypothesis.
-Oceans, glaciers, rivers, lakes, air, soil, and living tissue; -Water evaporates from the ocean, plants, and soil; moves through the atmosphere, and eventually falls as precipitation (rain)
List the hydrosphere's major reservoirs, and describe the different paths that water takes though the hydrologic cycle
-lithosphere- strong, rigid layer, thinner; these are the plates; the crust; uppermost/coolest mantle -asthenosphere- weak, hotter, flowing; this layer *moves the plates* -rocks are nearly melted at this temp and pressure -respond to forces by flowing -moves independently from lithosphere (check! -> explain importance of plate tectonics theory??)
List the major differences between Earth's lithosphere and asthenosphere and explain the importance of each in the plate tectonics theory
generally, *lithosphere is less dense* and is *brittle* as opposed to the *asthenosphere*, which is *hot and ductile* (like Silly Putty) -bc the asthenosphere is ductile and without strength it *allows the plates to move over it* (slowly).
List the major differences between Earth's lithosphere and asthenosphere and explain the importance of each in the plate tectonics theory
Divide: Appalachian Mountains Watershed: Missouri River Basin Tributary: Big Horn River Trunk Stream: Mississippi River
Match the following geological features w/ the correct term (divide, water shed, tributary, trunk stream): -Big Horn River -Missouri River Basin -Mississippi River -Appalachian Mtns
-If the stream is in flood it can erode banks -As stream flow falls and it loses energy, it will deposit sediment
Outline the ways in which streams erode, transport, and deposit sediment
volume
P waves temporarily change the ---- of material
convection
Plate tectonics and plume generation are thought to be ultimately driven by....
shape
S waves change the ----- of material
Seafloor spreading occurs at divergent plate boundaries. As tectonic plates slowly move away from each other, heat from the mantle's convection currents makes the crust more plastic and less dense. The less-dense material rises, often forming a mountain or elevated area of the seafloor. (google pic; practice drawing to describe)
Sketch and describe the movement along a divergent plate boundary (sea-floor spreading) that results in the formation of new oceanic lithosphere
b
Subduction zones and deep oceanic trenches are associated w/ a a) divergent boundary b) convergent boundary c) transform boundary d) hotspot e) none of these
- Mantle plumes extend form mantle-core boundary and cause convection within the mantle
Summarize what is meant by plate-mantle convection
an ocean
The East African rift is a divergent plate boundary that is splitting the continent of Africa into two pieces. What will eventually form around this divergent boundary?
-suggested that the continents broke through thinner oceanic crust as they migrated over time
Wegener's statement that led to the ultimate rejection of continental drift as a hypothesis about continental movement
Both waves travel along Earth's surface and decrease in amplitude with depth below the surface
What do vertical and horizontal surface waves have in common?
how liquid and gaseous water move between the ocean, atmosphere, and land.
What does the hydrologic cycle describe?
-subducting plates -upwelling of hot rock
What drives plate motions: -this drives the *downward* component of *convection* -this drives the *upward* component of *convection*
-increasing flow *v*elocity increases *t*urbidity (muddiness of stream) (VT) -most stream flow is turbulent (-water moves erratically in a swirling motion -lifts sediment from streambed)
What factors cause streamflow to change
-the atmosphere would contain less water -the oceans would become smaller -Gulf of Mexico (Illinois is located in the Mississippi River drainage basin. The Mississippi River empties into the Gulf of Mexico)
What would happen to atmospheric water if Earth were mostly covered with land? What would happen to the oceans if surface runoff and groundwater flow were reduced (for example, by the growth of ice sheets during an ice age)? Water falling in Illinois would ultimately end up where?
-it's hot gas released during a volcano which can hurt living organisms, air quality and even airplane engines -it can include releasing ash and other volcanic materials and it moves very fast down the side of the volcano so it's hard to outrun
What's pyroclastic flow and why is it so dangerous
-when cold, dense *oceanic* crust sinks bc it's denser than the asthenosphere -part of convection/what drives plate motions
What's slab pull
a) the subducting slab supplies water to a wedge of hot mantle rock thereby lowering its melting temp
What's the main factor that triggers the formation of magma when a cold slab of oceanic lithosphere is subducted
at Earth's surface
Where are tectonic plates located
Body waves travel within Earth; surface waves travel along Earth's surface
Where do body waves and surface waves travel?
on earth's surface, directly above the hypocenter (think: hypo means under, and epi means above)
Where is the epicenter of an earthquake?
b and c (focus and hypocenter are same thing?)
Which of the following are true of earthquakes? a) An earthquake builds up strain in the rock. b) An earthquake originates at the focus. c) An earthquake occurs after strain has built up in the rocks. d) An earthquake originates at the epicenter. e) An earthquake is always preceded by aftershocks.
d
Which of the following has provided the best means for us to learn about the layered structure of Earth? a) X-rays of the interior b) infrared technology c) locations of volcanic activity d) study of seismic waves
c
Which of the following increases the viscosity of magma a) a decrease in ash content b) an increase in temperature c) an increase in silica content d) a change in the color of magma e) an increase in gas content
e
Which of the following is consistent with the plate tectonic theory? a) Convection driven by cool rocks rising in the mantle moves the overlying lithosphere. b) Lithosphere convection drives mantle movement. c) Lunar tidal forces drive continental movement. d) Gravity-driven "ridge push" moves plates at convergent plate boundaries. e) As a plate sinks into the asthenosphere, it pulls the trailing plate along.
c
Which of the following statements about Earth's magnetic field is most accurate? a) Earth's magnetic field does not switch polarity. b) Earth's magnetic field switches polarity at regular time intervals. c) Earth's magnetic field switches polarity at irregular time intervals. d) Earth does not have a regular magnetic field.
a (While drainage basins only have one trunk river, many tributary rivers can flow into this trunk river within the drainage basin)
Which of the following statements about drainage basins is false a) Drainage basins only contain one river. b) All water leaves a drainage basin through one river. c) A trunk stream for one drainage basin can be a tributary for a larger drainage basin. d) Water falling on opposite sides of a divide will flow in different directions.
b
Which of the following statements about earthquakes with magnitude greater than 4.0 is most accurate? a) Earthquakes with magnitude greater than 4.0 occur in a pattern than correlates closely with hot spots b) Earthquakes with magnitude greater than 4.0 occur in a pattern than correlates closely with plate boundaries c) Earthquakes with magnitude greater than 4.0 occur in a pattern than correlates loosely with plate boundaries d) Earthquakes with magnitude greater than 4.0 occur in a pattern than correlates loosely with hot spots.
b
Which of the following statements most accurately describes the volcanoes of the Hawaiian Islands, USA a) they occur along a mid-Pacific transform fault b) they're fed by a long-lived hot spot deep below the Pacific lithospheric plates c) they're associated w/ a mid-Pacific ocean ridge and seafloor spreading d) they're associated w/ subduction and convergent plate boundaries e) they're forming along an island arc
d
Which of the following theories about continents and ocean basins is correct? a) Continents and ocean basins have fixed geographic positions b) The continents moved apart approximately 200 million years ago, but are now stationary c) Continents move by plowing through oceanic crust. d) Plate material is formed at divergent plate boundaries and consumed at convergent plate boundaries. e) Ocean basins do not expand or contract.
hot spots
Which phenomenon can explain the presence of volcanoes in the middle of the Pacific Ocean?
divergent
Which type of plate boundary is most closely associated with the formation of new ocean floor?
pyroclastic flows
Which type of volcanic hazard results in a very fast-moving cloud of super-heated ash and toxic gases?
Transform boundaries do not cause changes to the pressure, temperature, or composition of the mantle
Why are volcanoes not found at transform boundaries?
rift valley
a *region* of Earth's crust along which divergence is taking place
-ocean crust being subducted under a continent (volcanoes form on the continent leading to a continental volcanic arc)
a continental volcanic arc is the result of...
magnetic time scale (google pics)
a scale that shows the ages of magnetic reversals and is based on the polarity of lava flows of various ages
3-10 cm/yr
approximate rate at which new oceanic crust is created at divergent boundaries
lava
erupted magma
-*a*ge and *t*hickness of seafloor sediment (sediment age increases w/ distance from ridge -sediment is thicker w/ increased distance from the ridge -oldest seafloor is 180 million years old) -*h*ot-spot tracks -apparent *p*olar wander -*m*agnetic reversals and seafloor spreading (AT-HP-MS)
evidence in support of the plate tectonic theory
San Andreas Fault
ex. of a transform plate boundary
-the heaviest (densest) material is at the center and the lightest is at the top -iron core; rocky mantle and crust; water ocean; gaseous atmosphere (Earth's interior is dynamic: mantle and crust are in motion; convection)
explain Earth's distinct layers
-*volcanoes increase* in *age w/ distance* from Hawaii (-a cylinder of upwelling hot rock (*mantle plume*) is beneath Hawaii -a *hot spot* is an area of volcanism, high heat flow, and crustal uplift above a mantle plume -a *hot-spot track* formed as the Pacific Plate moved over the hot spot)
explain how Hawaiian volcanoes support Plate Tectonics Model
-Basalt erupts above the *curie temp* so magnetite grains are nonmagnetic -grains align to magnetic field during cooling -rock preserve a record of the direction of magnetic poles at the time of formation (Paleomagnetism or fossil magnetism)
explain how Iron-rich minerals are influenced by magnetic pole (part of testing the Plate Tectonics Model)
-convergent: lithosphere is destroyed -divergent: lithosphere is formed -transform: lithosphere is neither formed nor destroyed
explain how the lithosphere is affected by the different plate boundaries
-convergent: earthquakes, volcanoes, mountain formation -divergent: earthquakes, volcanoes, *volcanic* mountain formation -transform- earthquakes
explain the geologic processes that occur for each of the plate boundaries
-divergent: spreading -convergent: subduction -transform: lateral sliding
explain the motion of the different plate boundaries
-states tectonic processes deform crust and create major structural features
explain the revolutionary new model of *tectonic processes* which came out after 1960
-divergent: ridge/rift -convergent: trench -transform: no major effect (DR; CT)
explain the topography of the different plate boundaries
-viscosity; *temperature*, *composition*, and *amount of dissolved gas* affect magma behavior (the nature of volcanic eruptions)
factors that account for the nature of volcanic eruptions
-viscosity, temp, composition and amount of dissolved gas
factors that affect magma behavior (the nature of volcanic eruptions)
-artificial *l*evees -flood control *d*ams -*c*hannelization (artificial cutoffs shorten the stream and increase gradient and velocity) -*nonstructural approaches may be more efficient* (LDC)
how can floods be controlled
the more viscosity the lava, the more explosive the eruption
how does viscosity affect the nature of volcanic eruptions
-increase temp -decrease silica content (-Rhyolitic magma (>70% Si) forms short flows -Basaltic magma (about 50% Si) is fluid) -add water
how to decrease magma viscosity (the nature of volcanic eruptions)
-increased small *e*arthquakes under the volcano, *i*nflation of ground, increased *h*eat flow and increased release of *g*ases indicate likelihood of activity (HIGE)
how volcanic activity can be predicted
evaporation (also via evapotranspiration; condensation; precipitation)
how water enters atmosphere from the oceans
-earthquakes, active volcanoes, varied earthquake depths at different epicenters -it's a convergent boundary where there's subduction, likely oceanic-continental bc so close to islands -there's a trench; at the tench the earthquakes are shallow and as you go further away, the earthquakes get deeper (at epicenters further from trench) -there's more than one volcanic island
in plate tectonic case study (geo activity): -What are the general signs that this is a plate boundary (or not)? -Is it the center of tectonic plate, a divergent boundary, a convergent boundary, or a transform boundary? Is it a hotspot? What's the evidence supporting your choice?
-subduction of *oceanic* lithosphere (-continental lithosphere is less dense -water from descending oceanic crust triggers partial melting of asthenosphere at about 100 km -molten material is less dense and rises (*continental volcanic arcs*) (-convergent plate boundaries and subduction)
oceanic lithosphere + continental lithosphere =...
transform
plate boundary not associated w/ volcanic eruptions
transform
plate boundary that would exhibit vertical faults w/ rock units that didn't match, offset stream channels, and strong earthquakes w/ no volcanoes
hanging wall block (rock surface below the fault is the foot-wall block)
rock surface above the fault (brittle deformation)
vibrations (Earthquake destruction)
soft sediment amplifies ---- which cause loosely packed, waterlogged materials to behave like a fluid (during liquefaction stable soil becomes mobile and rises to the surface) -these also trigger landslides, ground subsidies, and fires
faults (-fractures in the crust w/ appreciable displacement -rock surface above the fault is the *hanging wall block* -surface below the fault is the *foot-wall block*)
structures formed by brittle deformation
slab pull
tectonic process associated with convection currents in Earth's mantle that occurs as the weight of the subducting plate *pulls the trailing lithosphere* into a subduction zone
a
the Richter Magnitude scale is based upon a) the amount of energy released as recorded by the largest amplitude of the shear waves b) observations of the severity of shaking and damage caused c) the amount and length of earth surface rupture and the strength of rocks involved d) the depth of an earthquake
-pyroclastic flows- hot volcanic *gas* infused in incandescent ash and lava fragments; gravity driven- can move up to 100 km/hr; low-density cloud of hot gases and fine ash on top of layer of vesicular pyroclastic material; caused by collapse of eruption columns -Lahars- fluid mudflows; water-saturated pyroclastic materials move down steep volcanic slopes -Lava flows -ash and volcanic gasses (ash can damage buildings, living things and air craft engines; gases like sulfur dioxide affects air quality and creates acid rain) (-tsunamis caused by collapse of volcano flanks into the ocean -atmospheric cooling- ash and aerosols reflect solar energy) (PLLG)
the different volcanic hazards
subduction of oceanic lithosphere (-volcanic island arcs, continental volcanic arcs -convergence: also reverse faults here -continent-continent convergence)
the driving force of orogenesis (mountain building)
convection flow
the heat transfer mechanism from Earth's interior
top layer: crust, mantle, outer core, inner core
the layers of the earth from the surface downward are:
rift valley
the longest topographic feature on Earth's surface
outer core
the one layer in Earth that will transmit only one type of wave based on its composition
-Seismic waves (-waves are reflected at boundaries -refracted through layers -velocity increases w/ depth -S waves don't pass through outer core, indicating it's liquid)
the only way we can 'see' inside the Earth's interior
Apparent Polar Wandering
the perceived movement of the poles in relation to the continent
earthquake damage
this depends on: -intensity/magnitude -duration -nature of surface materials -nature of building materials -construction practices
large, cyclical
transform and strike-slip faults generate ----- earthquakes
-surface waves; body waves (P and S waves)
two main types of seismic waves generated by earthquakes
surface and body waves
two primary types of waves generated by earthquakes
-Primary or P waves; Secondary or S waves
two types of body waves
ductile deformation
type of deformation where some chemical bonds break and new ones form
strike-slip
type of fault
convergent
type of plate boundary that's most closely associated with uplifting continental regions and mountain building
-*mantle* convective flow drives plate motion (-mantle is solid, but heat and weak enough to flow -*convection* occurs as hot, less dense material rises and surface material cools and sinks) (-*subducting* plates drive *downward component* of convection -*upwelling* of hot rock -during *slab pull*, cold, dense oceanic crust sinks bc it's denser than the asthenosphere)
what drives plate motions
new oceanic lithosphere
what forms at divergent plate boundaries
the Sun
what powers the Hydrologic cycle
-intensity and duration of rainfall -amount of water already in the soil -nature of the surface material -slope of the land -extent and type of vegetation
what precipitation that forms runoff depends on
-Intensity and duration of rainfall -Amount of water already in the soil -Nature of the surface material -Slope of the land -Extent and type of vegetation
what precipitation that forms runoff depends on - - - - -
-water that flows over the ground surface rather than soaking into the ground (precipitation that forms runoff depends on: -intensity and duration of rainfall -amount of water already in the soil -nature of the surface material -slope of the land -extent and type of vegetation)
what's runoff
the size of seismic waves
what's the magnitude the Richter Scale measures based on
-*tectonic motion* builds up stress -friction keeps the fault from slipping -*slip* initiates when *stress overcomes friction* (-elastic rebound causes deformed rock to spring back to underformed position)
when do destructive earthquakes occur
intraplate volcanism
where a mantle plume of hot material ascends to the surface
-along the *crests* of oceanic ridges (-new ocean floor is generated when mantle fills narrow fractures in oceanic crust)
where most divergent plate boundaries are
-Ring of Fire around the Pacific Ocean -Mid-ocean ridges (few are randomly distributed)
where most volcanoes are found near
convergent boundaries (where young mountain belts are found; remember convergent boundaries = mountain building)
where's Earth major mountain belts
divergent
which boundary involves continental rifting
-physical and chemical segregation of molten material after initial formation (-temp increased as material accumulated to form Earth: -Iron and nickel melted and sank to the center to produce iron-rich core -buoyant rock rose to the surface and formed crust -chemical segregation led to iron-rich core, primitive crust, and mantle)
why the Earth is layered
continental collision
why there's earthquakes along Alpine-Himalayan belt
bc tension pulls plates apart
why there's weak earthquakes along oceanic ridge system
he didn't have a good mechanism for explaining continental drift
why was Wegener's hypothesis of continental drift not taken seriously by most geologists