GEOL 1340 - EXAM 3

Composite volcanoes are constructed of what? and associated with what?

Constructed of alternating pyroclastic deposits and lava flows. Associated with convergent plate boundaries (Andes & Cascades)

detritial sedimentary rock

- clastic - form from pre-existing particles - classified by size of particles

3 types/groups of seismic waves?

- surface waves - P waves - S waves

3 types of differential stress

1) compressional 2) tension 3) shear

Angles of response:

Angle of response is the max angle a slope can have and still be stable. Ranges from 33 to 37 degrees for most materials Angle of response depends on several factors: - Coarser materials can have steeper slopes - cohesiveness and internal friction of the material: ~ Wet, unsaturated sand is more cohesive than dry sand this can have steeper slope..... ~... but too much water can destroy cohesion lead to slope failure

Contact metamorphism of country rock along the margins of a magmatic intrusion produces a zone of high-temp alteration called?

Aureole

Mass Wasting:

The transfer of rock and soil up slope under the influence of gravity

Continental shield:

a region where a craton is exposed at the surface

S waves

arrive at the station next (second)

Declination:

compass direction points to magnetic north pole

How is magma generated beneath mid ocean ridges?

decompression melting

Felsic:

further magmatic differentiation results in more highly evolved melting (granite & rhyolite)

What is the composition of the outer core?

liquid iron

divergent boundary

move apart

what is the basic building block of all silicate minerals?

silicon oxygen tetrahedron

Which seismic waves do the most damage in earthquakes?

surface waves

P waves

travel the FASTEST. Arrives at station first.

Sedimentary rocks (3 major groups)

(1) Detrital (clastic): composed of particles of pre-existing rocks (2)Chemical/Biochemical: precipitated by water sometimes w/ aid of marine organisms (3) Organic: composed mostly of the remains of plants/animals

Matching (HAVE TO LOOK AT POWER POINTS TO SEE IMAGE ASSOCIATED WITH ANSWER CHOICE) (1) rotational slide (2) mud flow (3) soil creep (4) debris avalanche (5) translational slide (6) rock fall

(1) E (2) F (3) A (4) D (5) C (6) B

Match each locatin w/ appropriate plae boundary: (1) Aleutian islands (2) Andes, South America (3)Cascades, NW U.S. (4) Himalayan Mts (5) Philippines (Mariana trench)

(1) Ocean - Ocean convergence (2) Ocean - Continent convergence (3) Ocean - Continent convergence (4) Continent - Continent convergence (5) Ocean - Ocean convergence

match the items with appropriate type of metamorphism: (1) margins of magma intrusion (2) colliding continents (3) blueschists & ecogites (4) mid ocean ridge (5) reactions w/ hot fluids (6) differential stress & foliated metamorphic rocks (7) shale -> slate -> schist -> gneiss (8)nonfoliated quartzite, marble, and hornfels

(1) contact metamorphism (2) Regional metamorphism (3) Subduction zone metamorphism (4) Hydrothermal metamorphism (5) Hydrothermal metamorphism (6) Regional metamorphism (7) Regional metamorphism (8) Contact metamorphism

Strike-slip faults:

- 1 block slips horizontally past the other - Results from shear stresses - Common along transform boundaries

Continents grow by:

- Addition of igneous material through partial melting of underlying mantle - Erosion of uplifted areas, followed by sediment deposition around the margins - Accretion of arc terrains & micro-continents around the margins - Collision & assembly w/ other continents

P - waves bend ____________ when entering the outer core due to a ___________ in velocity, and bend again when they leave.

- DOWNWARD - DECREASE

Thrust or Reverse faults:

- Hanging wall moved upward relative to the footwall - Results from compressional stresses - Common along convergent boundaries

Normal fault:

- Hanging wall slips downward relative to footwall - Results from tensional stresses - Common along divergent boundaries

Major processes that have contributed to Earth's internal heat:

- Heat released by colliding particles during the formation of Earth - Heat released during gravitational contraction of early Earth - Heat emitted by radioactive decay of unstable isotopes within Earth - Early impact w/ a Mars-sized object - Heat released as iron crystallized to form the solid inner core

Lithosphere

- Includes crust & solid upper portion of mantle - cool, rigid layer - average 100 km thickness (but can be 250 km + thick beneath older portions of continents) - broken into series of plates

Cratons

- Nuclei of ancient crystalline rocks - Found on all continents - Date to Precambrian (600 m.y old) - Regions of thickest lithosphere

Liquid iron in the outer core is stirred into _______________ motion by Earth's rotation and internal heat. Circulation of the liquid iron produces ________ currents. These electric currents, in turn, generate Earth's ___________ ______.

- convective - electric - magnetic field

Shield volcanoes are associated with what? and constructed of what?

- mantle plumes - Basaltic lave flows (Hawaiian islands)

Igneous Rocks:

- melting of ultramafic mantle (peridoitite) forms mafic (basaltic) magma - Magma then rises towards the surface and compositionally evolves as it cools & crystallizes minerals to form igneous rocks

Seismic waves arrive at a seismograph station in 3 distinct group:

- surface waves - P waves - S waves

Role of volatiles:

- the additon of volatiles (primarily water) causes rocks to melt at lower temps. - important factor where oceanic lithosphere descends into the mantle.

chemical and biochemical sedimentary rocks

- the dissolves products (ions) of weathering are transported to large bodies of water by rivers/streams - dissolved ions are eventually precipitated from water (usually seawater) by chemical & biochemical reactions to form chemical/biochemical sediment

3 types of plate tectonics (be able to identify in illustrations, look in powerpoint slides)

1) Divergent plate boundaries 2) Convergent plate boundaries 3) Transform plate boundaries

Match with appropriate plate boundary or other feature: 1) divergent boundary 2) convergent boundary 3) lateral strike-slip motion 4) creation of new oceanic lithosphere 5) destruction of oceanic lithosphere 6) Hawaiian islands 7) San Andres fault

1) Mid-Ocean ridge 2) Subduction zone 3) Transform plate boundary 4) Mid-Ocean ridge 5) Subduction zone 6) Mantle plume/ hot spot 7) Transform plate boundary

Evidence for continental drift?

1) fit of continents 2) fossil evidence 3) geologic matches 4) paleoclimates 5) paleomagnetism

What 3 cycles compromise the geologic cycle?

1) hydrologic cycle 2) rock cycle 3) tectonic cycle

what 5 criteria define a mineral?

1) naturally occurring; generally found in nature 2) solid within temp ranges normally found at Earth's surface 3) Orderly crystalline structure where atoms are arranged in an orderly, repetitive manner 4) well-defined chemical composition 5) generally inorganic even though some may contain carbon

Seismic tomography: (LOOK AT EXAMPLE IN SLIDES)

3D model of Earth's interior based on seismic imaging. Requires seismic records from many diff earthquakes Identifies regions where P- & S- waves are faster/slower than average Velocity variations of seismic waves are attributed to variable temps & other material properties: - warmer temps = slower velocity (RED) - cooler temps = faster velocity (BLUE)

Slope Stability:

A slope is an open system seeking a stable angle of equilibrium A lope strives for a balance among several conflicting forces: - gravity - frictional resistance b/w the slope & particles - Inertia (tendency of particles to remain at rest) - cohesion and internal friction of particles

What is the composition of the inner core?

Solid iron

What is the lowest level at which a stream will erode?

Base level

S- waves _____ ____ travel through the outer core

CAN NOT

classification of chemical and biochemical sedimentary rocks:

Classified by composition. Carbonates: - limestone (composed of calcite with or without fossil shells) - chalk (carbonate rock composed of microscopic shells) - dolostone (Mg-rich carbonate rock composed of dolomite) Siliceous rocks: - Chert & flint (composed of microcrystalline quartz) Evaporites (rock gypsum,rock salt) Organic (coal forms from burial/alteration of plant matter)

Domes & Basins: Strata exposed at the surface form ___________ circles around a central point

Concentric

How does continental crust differ from oceanic crust in terms of thickness and composition?

Continental crust is thicker and less dense than oceanic crust. Continental crust consists of granite, whereas oceanic crust is composed of basalt and gabbro (primarily)

Where is the asthenosphere located?

below the lithosphere, in upper mantle

Non- silicate minerals include:

calcite (carbonate) dolomite (carbonate) halite (halide) gypsum (sulfate) hematite (oxide) magnetite (oxide) galena (sulfide) chalcopyrite (sulfide) fluorite (halide)

Lava types vary based on what?

composition, temp, silica content and amount of dissolved gasses. Fluid lava flow, lava fountain, thick lava flow, pyroclastic eruption

D" Layer (thin layer b/w outer core & mantle) =

conduction

How is heat transferred in the crust?

conduction

Inner core (solid iron) =

conduction

lithosphere =

conduction

Outer core (liquid iron) =

conduction & convection

Accreted Terranes:

continental growth by assembling of micro-continents, arcs, and other crustal fragments accreted along the edge of a continent adjacent to a subduction zone

How is heat transferred in the mantle?

convection

Describe brittle deformation?

cracks

what 2 layers compromise the lithosphere?

crust & upper mantle

magma composition changes through what?

crystallization of minerals and assimilation of crust

regional metamorphism of shale forms different _______ ____________ _______

foliated metamorphic rocks

Earth's internal temperature INCREASE with depth at a rate known as the ________________ ____________. - varies considerably from place to place. - average about 20 - 30 degrees Celsius per km in crust - increases dramatically w/ depth, reaching ~5,500 degree Celsius in inner core

geothermal gradient

Mafic:

igneous activity produces rocks having the compositions of the initial magma (gabbro & basalt)

Individual tetrahedra can what?

link together to form a variety of silicates

asthenosphere (weak sphere)

located in upper mantle below lithosphere Small amount of melting in the upper asthenosphere mechanically detaches it from overlying lithosphere the lower asthenosphere is SOLID

What is the source of earth's internal heat today?

long lived radioactive isotopes that continue to decay in the interior keep earth hot

what is the composition of magma generated though partial melting of mantle periodotite?

mafic

intermidiate:

magmatic differentiation (crystallization and setting) changes the compostion of the remaining melt. (diorite & andesite)

The Wilson Cycle (cont)

Declining stage: e.g. Pacific Ocean Remnant Stage: e.g. Mediterranean Sea Suture Zone: e.g. Himalayan Mnts

Stream actively down cutting towards its base level produces what?

Deep, narrow valley

Under what conditions will ductile deformation be favored over brittle deformation?

Ductile has higher temp & pressure whereas brittle has low temp and pressure

Wave fronts

Energy travels away from the focus as seismic waves

What generates the Earth's magnetic field?

Fluid motion of liquid iron in outer core

Folds:

Folds are twists and bends in rocks. Folds result from ductile deformation of rocks in response to compressional stress by external forces: - Anticlines are layers rocks that folded into arches - Synclines are layered rocks folded into troughs

foliated metamorphic rock

Foliated Metamorphic rocks exhibit preferential alignment of platy minerals or other features in a common direction. Requires differential stress Foliation can form in various ways including: - rotation of platy and/or elongated minerals - re crystallization of minerals in the direction of preferred orientation - changing the shape of equidimensional grains into elongated shapes that are aligned

Earth's increasing temperature w/ depth is represented by what?

Geothermal Gradient

Regional Metamorphism

High temp & pressure over large areas. Intense alteration of original rock: - recrystallization & formation of new minerals - original sedimentary layering and/or structures destroyed Caused by major tectonic forces associated w/ mountain-building along convergent plate boundaries

What are endogenic processes?

Igneous activity, metamorphism, orogenesis

Outer Core is composed of ________ Iron, whereas the Inner Core is composed of _________ Iron.

Outer core = LIQUID Iron Inner core = SOLID Iron

how are P & S waves affected when passing through the asthenosphere?

P & S waves slow down b/c the asthenosphere is a weak layer. It is considered the "low velocity zone" b/c it slows down seismic waves

Bending of P waves in the outer core creates what?

P wave shadow zone

what happens to P- & S- waves that encounter the outer core?

P waves slow down. S waves can NOT travel through the outer core b/c they cant travel though liquid

What principle rock type comprises the asthenosphere?

Peridotite

Transform Fault Boundaries:

Plates slide laterally past one another so that lithosphere is neither created nor destroyed. Transform faults are important features in ocean basins & on continents: - most join segments of a mid ocean ridge along breaks in the oceanic crust known as fracture zones - a few (the San Andres fault and the Alpine fault of New Zealand) cut through continental crust

Crustal Deformation Processes

Rocks subjected to powerful tectonic forces, deep burial, and gravity will eventually deform. Types of deformation: - Folding: rocks bent & contorted - Faulting: rocks break/slip & slip along a plane of dislocation Plate boundaries are typically sites of crustal deformation

which 2 of the 3 groups of seismic waves are body waves that travel through Earths's deep interior?

S and P waves (body waves; they give us info about the Earth's interior)

Formation of sedimentary rocks:

STEP 1) Chemical and mechanical weathering break down rock. STEP 2) Erosional agents transport sediment STEP 3) Deposition occurs when solid particles settle out or when ions in solution are precipitated by inorganic or biological processes STEP 4) Diagenesis - burial and trafsormation into sedimentary rock

non-silica minerals lack what?

Silica Tetrahedra (SiO4)

Hypocenter (focus)

Site of initial fault slippage

Karst topography results from what?

Slightly acidic ground water dissolving limestone bedrock. (cave features form above the water table)

Weathering forms sediments:

Solid Earth interactions w/ hydrosphere & atmosphere at Earth's surface breaks down rocks (weathering) to form sediment. Products of weathering include: - Rock fragments from mechanical weathering - Clay minerals and/or iron oxide as products of chemical weathering - Dissolved ions into solution

Do seismic waves speed up or slow down in the inner core?

Speed up (b/c of the high density and solid nature)

Formation of liner island chains (LOOK AT PICTURE)

Stationary hot spot. Volcano forms over hot spot. Volcanism shits off as area moves away. Plate Moves over a hot spot. Plate subsides as cools.

Classification of slope failure:

Type of material: - solid rock - unconsolidated material ( sediment, soil or mixture called debris) Mechanism of movement: - Fall (free fall from a near-vertical face) - Slide (rock or material moves as a coherent mass down-slope) - Flow (rock or material moves as incoherent material down-slope) Rate of Movement: - Fast - Slow

Types of eruptions

Volcanic eruptions can be mild (effusive) or explosive. Factors that influence type of volcanic eruption: - temp of magma (hotter or more fluid) - Magma chemistry and viscosity: (low silica magma is more fluid; high silica magma is thicker and flows sluggishly) - Dissolved Gases: higher gas content and greater viscosity lead to more explosive eruptions.

Weathering:

the physical breakdown (disintegration) and chemical alteration (decomposition) of rock at earth surface

Eriosion:

the physical removal of material by mobile agents such as water, wind, ice, or gravity

interplate volcanism is associated with what?

mantle plumes & hot spots

Tansform boundary

move horizontally past one another

convergent boundary

move toward each-other

S wave shadow zone:

much larger than P wave shadow zone

what is the 1 major criteria that distinguishes silicate from non-silicate minerals?

non-silicate is not composed of silicon oxygen tetrahedron

Wilson cycle: (look at pics)

opening and closing of ocean basins - Crustal doming - Rifting - Linear Sea - Mature Ocean

Most earthquakes and volcanoes occur along what?

plate boundaries

Early ideas of continental drift gradually evolved into the modern theory of what?

plate tectonics

Epicenter

point on surface directly above hypocenter

atmosphere =

radiation

How is magma generated along convergent plate boundaries?

release of volatiles

Earths magnetic field has ________ polarity many times in the past (know picture in powerpoints)

reversed

is the lithosphere rigid or weak?

rigid & very strong

Silicate minerals are composed of _________ _______________________ bound together by CATIONS (e.g. Mg, Fe, Ca, K)

silica tetrahedra (SiO4)

Cinder cones:

small and constructed mainly of pyroclastic material

Surface waves

surface waves are the SLOWEST, they arrive last (third).

Metamorphic rocks have undergone changes in mineralogy, texture and/or chemical composition as a result of changes in what?

temp & pressure

classification of igneous rocks

the classification of igneous rocks is mainly based on compostion (silica content) and texture (mineral sizes) - Ultramafic: <45% Sio2 - Mafic: 45 to 52% siO2 - Intermediate: 52 to 65% SiO2 - Felsic: >65% SiO2

describe ductile deformation?

change shape without breaking or fracturing

Orogenesis:

An orogeny is a mountain-building event. Orogenies typically associated w/ convergent boundaries. 3 types of convergent plate boundaries: - (1) OCEAN - OCEAN - (2) OCEAN - CONTINENT - (3) CONTINENT -CONTINENT

supercontinent cycle

2 Major super continents existed over the last 1 billion years: - RODINIA: Assembled ~1 b.y ago & began to break apart ~600 m.y ago - PANGEA: Assembled by 230 m.y ago & began to break apart ~200 m/y ago BOTH may be products of the super continent cycle

Oceanic crust:

3 to 15 km thick Consists primarily of basalt * gabbro More dense than continental crust

Inclination:

Magnetic inclination is the angle a compass needle makes w/ Earth's surface and is a function of latitude

Know Earths internal structure - know where they are located, their destiny, composition, etc.

Inner core outer core lower mantle upper mantle asthenosphere crust (continental & oceanic) lithosphere atmosphere

Seafloor magnetic stripes:

Mid ocean ridges are divergent plate boundaries where new oceanic crust forms Spreading along the ridge pushes older rocks aside as new crust forms: - this would occur in conjunction with occasional flips in Earth's magnetic field Explains the alternating bands of normal and reverse polarity recorded in oceanic crust on both sides of mid ocean ridges

Measuring Earth quakes:

Modified Merclli Scale: - ranged from I - XII - based on amount of damage Richter Scale: - numeric scale - based on the amplitude of seismic waves Moment Magnitude Scale: - measured the energy released by earthquakes - considers amount of fault slippage & nature of the bedrock

Non-Foliated Metamorphic Rock

No preferntial alignment of minerals or other features Some types of metamorphism lack the conditions for forming foliated textures: - contact metamorphism - hydrothermal metamorphism - metamorphism of rocks w/o platy minerals

New oceanic lithosphere formed at mid ocean ridge is ultimately?

destroyed along convergent plate boundary

Transform boundaries do not form what?

volcanic activity (only hurricanes)

intraplate volcanism

volcanic activity that occurs within the interior of plates (away from plate boundaries) are associated with mantle plumes and hot spots

Hydrothermal metamorphism results from reactions b/w what?

warm fluid & rock

Earth's external processes

weathering mass wasting erosion

what are exogenic processes?

weathering, erosion, mass wasting

Stream reaches base level and side to side erosion creates what?

wide flood plain and meanders

continental crust:

~40 to 65 km thick Average composition of granite Less dense (buoyant) than oceanic crust