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Geology > Ch. 2 > Flashcards

Ch. 2 Flashcards

1
Q

what brought more evidence for COntinental drift

A

mapping the ocean floor (Marie Tharp)

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2
Q

Convergent Boundaries

A

lithospheric [plate moves toward each other
crust experiences compression- shortening and thickening of crust, crust recycled into mantle
Subduction and conitnental collision

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3
Q

Plate tectonics with NW native American myths

A

thunderbird and whale has terrible fight-
St Helens and Adams both belong to Rainer, fight and Helens blew her top and unheaded Rainer

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4
Q

Continetal collision is characterized by

A

tall broad mountains
little to no volcanoes
broad zones of freqeutn earthquakes (moderate to strong)

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5
Q

rate of spreading

A

width of stripes/ time duration

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6
Q

Evidence of continental drift analysis

A

coastlines of continents fit together like pieces- used contintal shelves
Observed matching rock formation, mountain, fossil, and glacial formations across oceans
(land-dwelling animals on different continents when not able to swim)
(evidence of glaciers in tropical parts and tropical animals in cold parts)

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7
Q

Transform boundary

A

plates slide horizontally, sideways, past each other in different directions (shearing motion)
faults at boundary called transform/stick slip fault
crust is not created or destroyed but transformed

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8
Q

Accretionary Wedge/Prism

A

scraped up/squish material from the subducted slab (highly deformed material)

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9
Q

where do majority of eathquakes and volcanoes fall

A

same location as the plate boundaries

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10
Q

Rock’s magnetism and Earth’s Magnetic field

A

when magma solidify, iron based inerals align themselves with earth;s current magnetic field

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11
Q

Continental rifts

A

continent breaking apart
crust thickening bc of extension, causing faults and crustal down-dropped blocks (rift valleys)
mantle meets up to crate, space below continents, mantle upwelling
as mantle upwells, ptrdsure descrease, metls form- bouyant and rises to top- volcanism
*** valleys within continents that have volcanoes and earthquakes **

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12
Q

slab pull

A

gravity pulls dense subducting slab in asthenosphere

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13
Q

OC-CC (oceanic to continental)

A

the denser one (OC) is subducted under CC

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14
Q

Failed contiental rifting

A

large scale rifting- multiple rift branches
some die out- no tectonic activity

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15
Q

Hotspots

A

area where magma breaks through OC or CC and creaes volcanic center, islands in ocean, and moutnain on land
NOT associated with plate boundaries
mantle plume is stable- but plarte moves causing bolcanic island- as plate mvoes, volcanic osurce cut off, forms new volcanic isalnd, sinks as gets colder

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16
Q

Divergent boundaries characteristics

A

crustal stretching/extension lead to normal faults and rift valleys (moderate earthwuakes occur)
volcanism common bc of decompression melting (formation of new crust)

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17
Q

movement of lithospheric plates

A

Slab pull
ridge push
mant;e convection (basal traction)

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18
Q

Rate of relative plate movement

A

measure position of GPS recievees over time
arrows show direction of motion, with highest rarte shwon by larger arrow
some arrow curve because plate rorating on spheres

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19
Q

Continental collision

A

2 continental lithospheric plates converging
no subduction- crust to buoyant
crust thickening, mountain building, high plateaus

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20
Q

Wadati-Benioff ZOnes

A

recognition of earthquake epicenters tracing shapes of oceanic plates that are sinking into the mantle
EQ epicenters starting at deep trenches on the ocean floor, concentrate along a descending plane angles beneath continents or island arcs
crust being pulled into mantles at the locations (convergent boundary)

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21
Q

What is primary cause of movement of lithosphere plates

A

slab pull

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22
Q

OC- OC

A

older (colder and denserO subducts under the uounger
trench- defines boundaryd

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23
Q

The wilson cycle

A

ongoing cyclical process of the origin and breakups of superconitinents

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24
Q

Continental Drift Analysis

A

1912, Alfred Weneger, all continentas connected but broke and drifted apart to present positions

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25
Q

Why was continental drift anaylsis rejected

A

not ahve the mechanism for continental movement

26
Q

The Wilson Cycle

A

J. Tuzco Wilson porposed cyclical process of opening and closing of oceans leading to breaking apart and reassembly of continents

27
Q

Subduction

A

Oceanic- Oceanic convergence and Oceanic-continental convergence
plates of different densities converge, the higher density plate is pushed beneath the more buoyant plate

28
Q

What do subduction zones produce

A

largest earthquakes and tsunamis
where deepest earthquales occur, along subducting slab and megathrust

29
Q

two types of rifts

A

narrow and broad

30
Q

transform boundary characteristics

A

no volcanoes or mountains- mainly earthquakes
most associeated with MOR- help accomodate for different rates of sea floor spreading
zig zag pattern

31
Q

ocean trench

A

deepest part, plate boundary at surface
OV subducts under CC, Causes CC to drag down and create deep crevice

32
Q

oceanic fracture zone

A

plates along fractures still moving in same direction

33
Q

Paleomagnetism

A

geologist study/measure the direction that magnetic minerals are oriented i nrocks and the strength of magnetism building a record of past magnetic polar changes- paleomagnetic record

34
Q

broad rifts

A

create parallel ridges and valleys
graben- downfaulted stack
horst- upfaulted block

35
Q

Seafloor Spreading

A

Harry Hess and ROvert Dietz- 1959-
propoed along Mid-Ocean Ridges-
Earth’s crust separates, new ocean crust is CREATED, newly formed ocean crust masss laterally, away from the ridge (divergent)

36
Q

what happens in continental rift continues

A

continent will break apart and a new ocean floor will form- sea floor spreading developed
edges of two new continents called passive margins (no plate boundaries are there

37
Q

Difference between magma with cc-oc and oc-oc

A

on cc-oc, its a mountain belt with volcano
on oc-oc, its a volcanic island arc (not island chain)

38
Q

PLate tectonics and Japanese culture

A

Namazu- the earthquaker
catfish undergound that causes earthquakes when shaking
Japan has 1/10 of the world’s earthquakes

39
Q

when was plate tectonic theory well established

A

1970s
total of 15 plates, named after conitnents

40
Q

Divergent boundaries

A

tensional forces and/or upwelling of mantle
plates move away from each other
continental rifts and Mid-ocean ridges (MOR)

41
Q

Earth’s magnetic field

A

generated by the outer core, iron is liquid and constantly moving (named dynamic effect)

42
Q

Magnetic pattern of ocean floor

A

caused by earth’s magnetic field flipping back and forth reversing polarity
supports sea floor spreading

43
Q

three types of plate motion

A

Divergent- move apart
Convergent - move towards each other
transform - move horizontally past each other

44
Q

seafloor spreading rates

A

width of stripe/time duration

45
Q

Magnetic stripes of the ocean floor

A

late 1950s, equipment to measure magnetic fields on ocean seafloor
the magnetic were alternating and mirrored each other on both sides

46
Q

Ocean drilling program

A

began 1960s
ships drill in sea floor, collect rocks and sediment
brought up oceanic crust (ages at multiple locations)
youngest crust lives along the MOR
HARD PROOF of sea floor spreading

47
Q

ophiolite

A

sequence of igneous rocks that represent a slice of oceanic crust
shows where ancient ocean floor was sceraped up ontio continental crust due to subduction

48
Q

Mantle Convection

A

hotter material rises and cooler mterial sinks- drag force along base of plates

49
Q

Continental converge in general

A

start with closing of ocean causign continents to join together

50
Q

How is drilling giving the hard proof of Seafloor spreafing

A

shows the age at multiple locations- youngest at the MOR
sediments on sea floor shows increasing thickness with distance away from ridge

51
Q

Cascadia earthquake

A

earthquake releases stress, falls down, water submerged again, ghost forect

52
Q

fold and thrust belt

A

lots of faults, deformed rocks,

53
Q

glacial strations

A

record direction of glacial flow

54
Q

narrow rifts

A

East African rift system- narrow and long

55
Q

Transform boundaries

A

continental transform fault occur along or within a continent as a single or sets of faults

56
Q

how MOR form

A

rift valley in center (spreading center)
mantle upwelling form 2 plates splitting- decompression melting
abyssal plain- where mantle upwelling occurs
hot and thin so bouyant- edges result in higher elevation for the ridges
as crust moves away, become scolder and older oceanic crust, falls down, flattens out, flat deep abyssal plains

57
Q

Mid ocean ridges

A

AKA spreading centers
oceanic plates move away from each other- widening of oceans
underwater ridges riaw 1 km above obyssal plain with rift valley in the center

58
Q

Himalayan Moiuntains

A

sea closed up, India slammed into Eurasis, stopped volcanism, expansion of Mt: himalayan and tibetan plateau

59
Q

Mapping of floor oceans

A

after WWII began mapping ocean floor using SONAR
Marie THarp and Bruce Heezen created first detailed map of the ocean floor and revealed the Mid-Atlantic ridge

60
Q

volcanic arc and mountain belt

A

as plates subducted, magma is forming and rises to form the heart of the mountains and creates volcanoes

61
Q

ridge push

A

gravity causes plates to slide away from topography of MOR, pushing plate outward

62
Q

Plate Tectonics

A

theory that layer of earth (Lithosphere) is broken into several plates that move relative to one another

Geology (8 decks)

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